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SECTION IV

RESULTS AND DISCUSSION

Results and Discussion

Page 85

CHAPTER– 1

PHY SIC O-CHE MICAL PROPERTIES, ANTINUTRIENT AND PROTEIN

PROFILE OF PEARL MILLET AS INFLUENC ED BY PROCESSING

Pearl millet has significant potential as food and feed in addition to its current

usage as forage. It is a drought-tolerant crop and can be grown under difficult

ecological conditions. For this reason it is widely grown in tropical regions of world

including Africa and Asia. It is comparable and even superior in some of the

nutritional characteristics to major cereals, with respect to its energy value, protein,

fat and minerals content (Abdalla et al. 1998). The use of pearl millet for human

consumption is limited due to non-availability in convenience form. The millet is

mostly used as whole flour for traditional food preparation and hence confined to

traditional consumers and to people of lower economic strata. Pearl millet can be

consumed raw after soaking and sprouting in form of salads but most of them require

cooking to improve digestibility, palatability and keeping quality. Two commercially

available pearl millet varieties such as Kalukombu (K) & Maharashtra Rabi Bajra

(MRB) were subjected to various processing methods [milling, wet and dry heat

treatments (Pressure cooking, boiling and roasting) and germination] commonly

adopted practices in Indian households and was studied for its influence on the

physico-chemical properties, nutrient composition, antinutrient profile as well as

influence of cooking medium which is a potential source of iron/calcium

contamination on total iron and calcium was explored. Total sugar and total soluble

protein of the raw and processed flours were also analyzed. Buffer-soluble proteins

were extracted from the raw and processed flours and separated by sodium dodecyl

sulfate – poly acrylamide gel electrophoresis (SDS-PAGE).


Page 86

Table 4.1. Proximate Composition of the Two Pearl Millet Varieties (per 100g)

Proximate composition Reported values* Analyzed values

Kalukombu MRB

Moisture (g) 12.4 10.1 9.6

Proteins (Nx6.25) (g) 11.6 9.3 10.2

Fat (g) 5.0 4.8 5.4

Ash (g) 2.3 2.0 1.5

Iron (mg) 8.0 5.0 6.4

Calcium (mg) 42.0 41.3 40.0

Phosphorus (mg) 296.0 327.8 255.7

Zinc (mg) 3.10 4.40 4.2

Copper (mg) 1.06 0.99 0.90

Manganese (mg) 1.15 1.61 1.78

Magnesium (mg) 137 99.34 105.08

Sodium (mg) 10.9 7.8 7.2

Potassium (mg) 307 200 180

* National Institute of Nutrition (NIN), Hyderabad, MRB – Maharashtra Rabi Bajra.

The proximate compositions of the two pearl millet varieties (K and MRB)

were determined and compared with the reported values (Table 4.1). K variety

contained 9.3% protein, 4.8% fat and 2.0% ash. Comparatively, MRB contained

higher protein (10.2%), fat (5.4%) and lower ash (1.5%) content. However, these


Page 87

values were similar to the reported values. The highest content of iron (6.4%) was

found in MRB while K had high phosphorus content (327.8%). Values for minerals

like calcium, zinc, copper and manganese were found to be similar for both varieties.

However, values for iron, zinc, manganese, magnesium, sodium and potassium

content were lower than the reported values.

Table 4.2. Bulk Density, Water and Oil Holding Capacity of Pearl Millet as

Influenced by Processing

Processing

Bulk Density

(ml/g)

Oil Holding Capacity

(g/g)

Water Holding Capacity

(g/g)

K MRB K MRB K MRB

WF (Raw) 1.68 a ± 0.1 1.65

a ± 0.2 1.38

a ± 0.1 1.18

a ± 0.0 0.88

a ± 0.11 0.95

a ± 0.05

SRF 1.84 ab

± 0.1 1.88 ab

± 0.1 1.43 a ± 0.1 1.35

a ± 0.1 1.13

a ± 0.08 1.08

a ± 0.08

BRF 1.93 b ± 0.0 2.03 c ± 0.0 2.87 b ± 0.0 3.00 b ± 0.0 3.13 d ± 0.09 2.97 d ± 0.05

Boiling 1.75 a ± 0.1 1.83

a ± 0.0 1.43

a ± 0.1 1.40

a ± 0.1 2.25

b ± 0.30 1.70

b ± 0.17

PC 1.75 a ± 0.0 1.80

a ± 0.1 1.25

a ± 0.2 1.50

a ± 0.1 2.38

c ± 0.04 2.23

c ± 0.30

Roasting 1.98 bc ± 0.0 2.00 bc ± 0.0 1.30 a ± 0.1 1.38 a ± 0.1 1.13 a ± 0.13 1.15 a ± 0.17

G 2.08 c ± 0.1 2.08

c ± 0.0 1.50

a ± 0.2 1.43

a ± 0.1 1.00

a ± 0.07 0.98

a ± 0.11

Values are mean ± SD (n = 4), Means with different superscripts (a, b, c, d) along the column are

significantly (P ≤ 0.05) different based on Tukey’s test. K – Kalukombu, MRB – Maharashtra Rabi

Bajra, WF – whole flour, SRF – semi refined flour, BRF – bran rich fraction, PC – pressure cooking, G

- germination


Page 88

Knowledge of physical/functional properties and their dependence on the

moisture content are useful for design and development of any processing methods

and equipment. Functional properties such as bulk density, water and oil holding

capacities of raw and processed pearl millet are presented in Table – 4.2. Bulk density

is an important parameter that determines the packaging requirement of a product

(Chandi et al 2007). The bulk densities of processed pearl millet flours (WF < Boiling

< PC < SRF < BRF < Roasting < Germination) were significantly (P ≤ 0:05) different

from each other, with whole flour (WF) having the lowest density (about 1.66 ml/g).

Germinated grains produced finer flours which led to its higher bulking capacity

(2.08ml/g). Interactions of water and oil with proteins are very important in the food

systems because of their effects on the flavor and texture of foods (Chandi et al 2007).

The oil holding capacity (OHC) ranged from 1.18 – 3.0 g/g for K and MRB. OHC of

the flours were not significantly (P ≤ 0.05) affected by different heat treatments and

germination respectively. However, bran rich fraction, a byproduct of milling, showed

highest OHC (3.00 and 2.87g/g for K and MRB respectively). Water absorption

capacities are related to the starch and protein contents and the particle size

distribution of the ingredient. The water holding capacity (WHC) of a sample is an

important determinant of stool-bulking effect, which is more related to the manner in

which water is held, rather than to the absolute amount held. These properties are also

important for stating the usefulness of the sample obtained as bulking, swelling and/or

thickening agents in formulations or foods of relatively high water activity

(Raghavendra et al 2004; De Escalada et al 2007). The water holding capacity (WHC)

ranged from 0.88 to 3.13 g/g for both varieties. BRF (3.13 and 2.97 g/g for K and

MRB respectively) and wet heat treatments such as boiling (2.25 and 1.70g/g for K


Page 89

and MRB respectively) and pressure cooking (2.38 and 2.23 g/g for K and MRB

respectively) presented highest WHC, whilst no significant (P ≤ 0:05) differences

were found between whole flour; semi refined flour, roasted or germinated flour. The

highest WHC of wet heat treated millet (boiling and pressure cooking respectively)

might be attributed to its lowest density among the processed samples. Flours with

lower bulk densities have larger surface area, polar groups, and uronic acid groups to

the surrounding water, leading to an increase in water absorption or swelling volume

(Bao et al 1994). However, this trend was not followed in case of BRF, which

exhibited highest bulk density, WHC and OHC. In this study, variations in the

functional properties (bulk density, WHC and OHC) amongst the processed millet

flours indicated that all these properties were affected by different preparation

methods.


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Table 4.3a. Swelling Power of Pearl Millet as Influenced by Processing (g/g)

Processing 55

oC 65

oC 75

oC 85

oC 95

oC

K MRB K MRB K MRB K MRB K MRB

WF (Raw) 2.77

a3 ±

0.02

2.94 b2

±

0.05

3.95 b2

±

0.05

3.31 c3

±

0.00

4.71 d4

±

0.05

4.91e4

±0.03

5.67 f3

±

0.01

6.05 g4

±

0.01

8.01 h5

± 0.02

10.01 i7

± 0.01

SRF 3.03 b4 ±

0.02

2.95 a2 ±

0.05

3.37 d4 ±

0.01

3.14 c2 ±

0.00

4.47 e2 ±

0.01

4.93 f4 ±

0.02

5.54 d2 ±

0.04

6.69 g3 ±

0.01

8.76 i7

± 0.03

8.80 i6

± 0.00

BRF 3.85 b5 ±

0.02

3.90 bc3 ±

0.00

3.72 a5 ±

0.01

3.94 c5 ±

0.02

4.63 d3 ±

0.04

4.80 e3 ±

0.00

6.06 f6 ±

0.00

6.32 g5 ±

0.02

8.57 i6

± 0.06

8.32 h4

± 0.01

Boling 4.87

b6 ±

0.03

4.56 a4

±

0.01

5.31 d6

±

0.03

5.24 c6

± 0.01

5.43 e5

±

0.02

5.86 fg6

±

0.02

5.83 g4

±

0.02

6.06 h4

±

0.04

6.48 i2

± 0.00

7.69 j3

± 0.00

PC 4.80 a6 ±

0.00

5.14 b5 ±

0.01

5.54 d7 ±

0.00

5.61 e7 ±

0.01

5.70 f6 ±

0.01

5.11 b5 ±

0.01

5.95 g5 ±

0.04

5.19 c2 ±

0.01

6.70 h3

± 0.00

6.67 h2

± 0.01

Roasting 2.61

a2 ±

0.00

2.88 b2

±

0.06

3.17 c3

±

0.05

2.62 a1

± 0.02

4.47 d2

±

0.00

4.72 e2

±

0.01

6.02 g6

±

0.02

5.73 f3

±

0.03

7.73 h4

± 0.00

8.41 i5

± 0.01

G 2.45

b1 ±

0.04

2.55 c1

± 0.04

2.35 a1

± 0.01

3.49 f4

±

0.04

3.39 e1

±

0.00

3.28 d1

±

0.02

3.29 d1

±

0.02

3.53 f1

±

0.01

3.63 g1

± 0.02

3.50 f1

± 0.00

Values are mean ± SD (n = 4), Means with different superscripts (a, b, c, d) along the row and means with different superscripts

(1, 2, 3, 4, 5, 6,7) along the column are significantly different (P ≤ 0.05), K –Kalukombu, MRB – Maharashtra Rabi Bajra, WF

– whole flour, SRF – Semi refined flour, BRF – bran rich fraction, PC – pressure cooking, G - germination


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Table 4.3b. Solubility of Pearl Millet as Influenced by Processing (g/g)

Processing 55 oC 65 oC 75 oC 85 oC 95 oC

K MRB K MRB K MRB K MRB K MRB

WF (Raw) 0.085

b12 ±

0.00

0.112b2

±

0.00

0.068b2

±

0.01

0.090b1

±

0.00

0.008a1

±

0.00

0.012a1

±

0.00

0.006a1

±

0.00

0.117b2

±

0.02

0.012a1

±

0.00

0.079b1

±

0.05

SRF 0.123

d23 ±

0.00

0.108cd2

±

0.00

0.112d5

±

0.00

0.105cd1

±

0.00

0.078bcd2

±

0.05

0.094cd34

±

0.00

0.002a1

±

0.00

0.075bcd1

±

0.00

0.067bc3

±

0.00

0.045b1

±

0.00

BRF 0.098

ab123 ±

0.00

0.150c34

±

0.01

0.095ab4

±

0.00

0.093b1

±

0.00

0.084a2

±

0.00

0.082a3

±

0.00

0.117ab4

±

0.02

0.117b2

±

0.00

0.093a4

±

0.00

0.075a1

±

0.00

Boiling 0.135d3 ±

0.00

0.164e4 ±

0.00

0.082b3 ±

0.00

0.113c1 ±

0.00

0.045a12 ±

0.00

0.117c5 ±

0.01

0.045a2 ±

0.00

0.106c2 ±

0.00

0.049a2 ±

0.00

0.090b1 ±

0.00

PC 0.109

c123 ±

0.01 0.130

d23

±0.01 0.060

a12 ±

0.00 0.082

b1 ±

0.00 0.081

b2 ±

0.00 0.104

c45 ±

0.00 0.070

ab3 ±

0.00

0.113c2

± 0.00

0.060a3

± 0.00

0.071ab1

± 0.00

Roasting 0.068

bc12 ±

0.00

0.060bc1

±0.00

0.055ab1

±

0.00

0.119f1

±

0.01

0.084de2

±

0.00

0.061bc2

±

0.00

0.074cde3

± 0.00

0.071bcd1

±

0.00

0.042a2

±

0.00

0.088e1

±

0.00

G 0.342

bc4 ±

0.04

0.426c5

±

0.02

0.248ab6

±

0.01

0.179a1

±

0.08

0.531d3

±

0.00

0.545d6

±

0.00

0.543d5

±

0.04

0.592d3

±

0.00

0.342bc5

±

0.03

0.408c2

±

0.01

Values are mean ± SD (n = 4), Means with different superscripts (a, b, c, d) along the row and means with different superscripts (1, 2, 3, 4, 5, 6,7) along the

column are significantly different (P ≤ 0.05), K –Kalukombu, MRB – Maharashtra Rabi Bajra, WF – whole flour, SRF – semi refined flour, BRF – bran rich

fraction, PC – pressure cooking, G - germination.


2

Swelling is a desirable physicochemical property making it useful in a range of

foods. The effect of temperature on swelling power and solubility of raw and processed

pearl millet is presented in table 4.3a&b. The swelling index is the measure of the ability

of the flour to absorb water and swell. Swelling power of raw and processed flours

increased with increase in temperature (55°C – 95°C). Swelling power of all the flours

significantly increased with increase in temperature. Whole flour had the highest value

(about 9g/g), while germinated flour had the lowest (3.5g/g) at 95oC.

Whole flour of K and MRB showed 8.5% and 11.2% solubility at 55oC. The

solubility of the millet after germination profoundly increased to 34.2 and 42.6% in K

and MRB respectively. Contrasting to swelling property, solubility of all the

processed flours decreased with the increasing temperature. For example, solubility of

processed flours was highest at 55oC and 65

oC, as the temperature increased from

75oC onwards the solubility of the flours decreased. For example, solubility of WF of

K and MRB was 0.085 and 0.112 g/g at 55oC which dipped to 0.012 and 0.079g/g at

95oC. Similar decreases were found in all processed flours except for germinated

flour. Germination altered the swelling and solubility of pearl millet. In germinated

flours, the decrease was not consistent, for instance, its solubility decreased at 65 o

C,

increased at temperatures 75oC – 85

oC and again decreased at 95

oC. The

solubilization of the flours progressively deceased with increasing in swelling power.

This result is different from that reported for corn (Yung et al 2006).


Page 93

Table 4. 4. Proximate Composition of Pearl Millet as Influenced by Processing

(Dry basis g/100g)

Processing

treatments Moisture Protein Fat Ash

Kalukombu

WF (Raw) 10.1 b

± 1.80

10.3 ab

± 1.08

5.3 bc

± 0.60

2.2 a ± 0.35

SRF 10.8 b ± 0.31 9.6

ab ± 0.75

5.0

bc ± 0.46

1.5

a ± 0.15

BRF 10.2 b ± 0.34 9.6

ab ± 0.70 7.8

d ± 0.77

3.6

c ± 0.36

Boiling 7.2 a± 0.30 7.9

a ± 0.26 5.2

c ± 0.26

1.3

a ± 0.29

PC 7.5 a ± 1.80 7.9

a ± 0.49 4.3

b ± 0.21

1.6

a ± 0.11

Roasting 6.6 a ± 0.40 8.1 a ± 1.64 4.4 b ± 0.19 1.9 b ± 0.08

Germination 7.4 a ± 0.10 10.4 b ± 1.27 3.4 a ± 0.12 2.0 b ± 0.04

Maharashtra Rabi Bajra

WF (Raw) 9.6 c ± 0.82 11.3 d ± 0.33 6.0 c ± 0.19 1.6 a ± 0.06

SRF 9.5 c ± 0.72 11.3 d ± 0.47 5.6 bc ± 0.14 1.4 a ± 0.17

BRF 9.5 c ± 0.30 9.4 bc ± 0.40 5.4 bc ± 0.24 3.9 b ± 0.09

Boiling 8.4 b ± 0.10

10.5

cd ± 0.20

3.9

a ± 0.32

1.5

a ± 0.08

PC 7.0 a ± 0.40

7.3

a ± 0.53

5.9

c ± 0.49

1.5

a ± 0.41

Roasting 6.4 a ± 0.20

7.9

ab ± 1.66

4.3

a ± 0.05

1.6

a ± 0.09

Germination 9.4 c ± 0.70

8.6

ab ± 1.53

5.1

b ± 0.81

1.5

a ± 0.02

Values are mean ± SD (n = 4), Means with different superscripts (a, b, c, d) along the column

are significantly different (P ≤ 0.05), WF – Whole flour, SRF – Semi refined flour, BRF –

Bran rich fraction.


Page 94

The proximate composition of processed pearl millet is presented in Table –

4.4. The moisture content of the flours were not altered by the process of milling or

germination however, heat treatments significantly (P ≤ 0.05) reduced the moisture

content in both varieties. The drying effect due to roasting caused a significant (P ≤

0.05) moisture loss in the millet. Reduction in moisture is favorable as high moisture

could possibly affect the storability of the product. The decrease in moisture content

upon roasting was in accordance with the earlier report (Komeine et al 2008).

Nonetheless the moisture content of all the flours, both raw and processed was below

the maximum moisture content limit (13%) for pearl millet flour recommended by

FAO/WHO (1995). This is the maximum allowable moisture content acceptable for

pearl millet flour meant for human consumption. The mean protein content of K and

MRB was 10.3% & 11.3% respectively. Processing did not affect the protein content

of K variety grains however; significant (P ≤ 0.05) reduction due to processing (heat

treatments, germination and bran rich fraction) was noticed in MRB. Reduction in wet

heat treatmented (boiling/pressure cooking) or germinated millet could be attributed

to leaching of water soluble and low molecular weight proteins into cooking/soaking

water (Alka et al 1997; Habiba 2002) while, decrease during roasting could be due to

destruction of amino acids as result of high temperature (Mauron 1982). The fat

content of K & MRB was 5.3% & 6.0% respectively. The BRF of K variety (7.8%)

retained significant (P ≤ 0.05) amount of fat content. The fat content of the heat

treated millet reduced significantly (P ≤ 0.05), could be attributed to its diffusion into

the cooking water or due to conversion of fat to fatty acid and glycerol which was

further hydrolyzed to acetate at high temperature (King et al 1987). Ash represents the

non-combustible fraction of the sample, i.e. minerals. The % ash content of K and


Page 95

MRB was 2.2% and 1.6% respectively. A significant (P ≤ 0.05) amount of ash content

was found in the bran rich fraction (3.6% in K & 3.9% in MRB). Roasting and

germination significantly (P ≤ 0.05) reduced ash content in K variety grains.The fat

and ash content reduced upon germination which could be due to losses of total

soluble solids during soaking prior to germination (Wang et al 1997).

Table 4.5. Mineral Content of Pearl Millet as Influenced by Processing

(Dry Basis, mg/100g)

Processing

treatments Iron Calcium Phosphorus

Kalukombu

WF (Raw) 5.9 c ± 0.35 45.7

a ± 4.54 364.0

b ± 33.67

SRF 4.6 b ± 0.52 51.0 abc ± 2.21 348.1 b ± 7.75

BRF 3.6 ab ± 0.01 61.5 d ± 1.52 307.9 b ± 71.53

Boiling 3.2 a ± 0.59 54.0

bc ± 1.41 225.2

a ± 27.5

PC 3.3 a ± 0.14 47.2

ab ± 2.37 241.8

a ± 17.0

Roasting 3.2 a ± 0.01 44.6

a ± 7.13 337.9

b ± 6.0

Germination 6.7 d ± 1.14 53.7 cd ± 4.50 239.0 a ± 11.4

MRB

WF (Raw) 7.1 c ± 1.50 44.2

ab ± 4.59 283.1

bc ± 36.9

SRF 6.5 bc

± 0.53 52.8 b ± 5.76 298.3

c ± 18.8

BRF 5.2 ab

± 0.80 85.9 c ± 8.30 392.0

d ± 31.4

Boiling 6.6 bc

± 1.77 53.3 b ± 2.21 257.6

abc ± 10.1

PC 7.3 c ± 0.42 52.4 b ± 2.27 247.7 ab ± 14.2

Roasting 4.0 a ± 0.26 39.6 a ± 9.46 262.4 abc ± 7.7

Germination 4.5a ± 0.49 53.7

b ± 3.25 221.5

a ± 21.1


are significantly different (P ≤ 0.05), MRB – Maharashtra Rabi Bajra, WF – Whole flour,

SRF – Semi refined flour, BRF – Bran rich fraction, PC – Pressure cooking.


Page 96

Table 4.5 depicts the mineral content of raw and processed pearl millet. The

total iron content was 5.6 & 7.1 mg/100g for K & MRB respectively. Pearl millet

subjected to milling and heat treatments significantly (P ≤ 0.05) lowered the iron

content whilst, a significant (P ≤ 0.05) increase in the germinated K variety was noted

which was in accordance with an earlier report on pearl millet (Sushma et al 2008).

This increase could be attributed to the mineral contamination in the water used for

soaking prior to germination. The total calcium content was 45.7 and 44.2 mg/100g in

K and MRB respectively. The bran rich fraction contained significant (P ≤ 0.05)

calcium levels. Pearl millet that was subjected to wet heat treatments or germination

had high calcium content. The total phosphorus content was significantly (P ≤ 0.05)

higher in K (364.0 mg %) compared to MRB (283.1 mg %). BRF of MRB contained

significantly (P ≤ 0.05) higher phosphorus whilst, wet heat treated K variety had low

phosphorus content. Similarly upon germination, the phosphorus content of the millet

reduced significantly (P ≤ 0.05).


Page 97

Table 4.6. Mineral Content of Processed Pearl Millet as Influence by Water

Type (dry basis, mg/100g)

Processing Iron Calcium Phosphorus

TW DMW TW DMW TW DMW

Kalukombu

Boiling 3.8 a ± 0.35 3.2

a ±0.59 53.3

a ±2.07 54.0

a ± 1.41 268.4

a ± 46.4 225.2

a ± 27.5

PC 4.6 b ± 0.49 3.3 a ±0.14 46.7 a± 3.76 47.2 a± 2.37 290.2 b± 42.7 241.8 a± 17.0

Germination 7.5 a ± 0.18 6.7 a ±1.14 54.7 a ± 1.82 53.7 a± 4.50 253.3 a± 26.2 239.0 a ±11.4

MRB

Boiling 6.6 a ± 1.43 6.6 a ± 1.77 54.0 a ± 3.1 53.3 a ± 2.2 256.9 a ± 12.3 257.6 a ± 10.1

PC 8.5 b ± 0.59 7.3 a ± 0.42 53.6 a ± 2.6 52.4 a ± 2.2 293.4 b ± 22.8 247.7 a ± 14.2

Germination 5.8 b ± 0.52 4.5

a ± 0.49 55.8

a ± 5.4 53.8

a ± 3.2 250.7

a ± 3.7 221.5

a ± 21.1

Values are mean ± SD (n = 4), means with different superscripts (a, b,) along the row are

significantly (P ≤ 0.05) different, MRB – Maharashtra rabi bajra, TW – tap water, DMW – de-

mineralized water, PC – Pressure cooking.


Page 98

Mineral contamination has been reported during the postharvest treatments of

cereals under uncontrolled conditions. Studies on the influence of iron pots and

utensils on iron content in a variety of foods have consistently shown that foods

cooked in iron pots and ⁄ or with iron utensils have significantly higher total iron

content than foods cooked with non-iron equipment (Prinsen et al 2003; Valerie et al

2011). Various food and water samples prepared in pots with and without an iron

ingot revealed low bioavailability of contaminant iron, while, approximately 75% of

the daily iron requirement was met by consuming 1L of lemon water prepared with an

iron ingot. Its use may be a cheap and sustainable means of improving iron intake for

those with iron-deficient diets (Christopher et al 2011). The introduction of iron pots

for the preparation of food may be a promising innovative intervention for reducing

iron deficiency and iron deficiency anemia (Prinsen et al 2003). Since this study was

an approach towards household practice, it was interesting to find out the extent of

contamination with extrinsic iron, calcium or potassium. Table 4.6 showed that

pressure cooked or germinated K variety millet, prepared using tap water had 1.3 and

48.4 mg/100g more iron and phosphorus than those prepared using de-mineralized

water. Similarly, pressure cooked MRB contained 1.2 and 45.7mg/100g more iron

and phosphorus. However, germinated MRB contained 1.3 mg/100g of more iron.

Millet cooked in tap water had around 1.3 mg/100 of iron and 47mg/100 of

phosphorus; however calcium contamination due to use of tap water for processes like

cooking or germination was not seen and also mineral transfer during the process of

boiling the millet was not seen.


Page 99

Table 4.7. Antinutrient Content of Pearl Millet as Influenced by Processing

Processing

treatments

Phytin

Phosphorus

(mg/100g)

Phytate

(g/100g)

Oxalate

(mg/100g)

Tannin

(g/100g)

Total Dietary

fiber (g/100g)

Kalukombu

WF (Raw) 219.1 c ± 5.50

0.78

c ± 0.02 36.0

b ± 4.90 0.23

c ± 0.01 13.3

a ± 1.80

SRF 186.6 b ± 18.30 0.66 b ± 0.06 45.2 c ± 1.94 0.21 b ± 0.01 9.20 a ± 0.20

BRF 277.7 d ± 17.30

0.99

d ± 0.06 65.8

d ± 10.4 0.31

d ± 0.01 28.0

b ± 5.00

Boiling 159.9 b ± 34.70 0.57 b ± 0.11 26.0 a ± 3.30 0.18 a ± 0.01 12.5 a ± 0.30

PC 164.5 b ± 12.60

0.58

b ± 0.04 35.3

b ± 2.10 0.18

a ± 0.01 12.6

a ± 0.70

Roasting 121.7 a ± 14.30 0.43 a ± 0.06 33.8 b ± 1.50 0.20 b ± 0.00 12.2 a ± 0.30

Germination 104.1 a

± 22.90

0.37 a

± 0.07 27.5 a ± 2.69 0.36

e ± 0.01 13.4

a ± 0.40

MRB

WF (Raw) 160.6 d ± 18.30 0.57 cd ± 0.07 31.6 b ± 1.10 0.21 a ± 0.02 11.9 a ± 1.80

SRF 93.2 ab

± 24.60

0.33 ab

± 0.09 41.8 c ± 0.97 0.19

a ± 0.01 10.6

a ± 0.40

BRF 326.5 d ± 13.60 0.61 d ± 0.10 58.4 d ± 8.27 0.32 b ± 0.01 29.1 b ± 7.80

Boiling 109.9 bc

± 12.50

0.39 ab

± 0.04

22.5 a ± 2.30 0.19

a ± 0.01 9.8

a ± 0.80

PC 167.8 d ± 16.20

0.60

d ± 0.06 30.7

b ± 3.20 0.22

a ± 0.02 11.1

a ± 0.20

Roasting 245.6 c ± 6.90

0.45

bc ± 0.11

22.6

b ± 3.70 0.23

a ± 0.03 11.7

a ± 1.00

Germination 75.60 a

± 3.20

0.26 a ± 0.01 16.4

a ± 1.77 0.28

a ± 0.01 9.7

a ± 0.10


are significantly different (P ≤ 0.05), MRB – Maharashtra rabi bajra, WF – Whole flour, SRF

– Semi refined flour, BRF – Bran rich fraction, PC – Pressure cooking.


Page 100

The antinutrient content of raw and processed pearl milled is presented in Table

4.7. The phytin P content of K variety was 219.1 and 160.6 mg/100g in MRB. The

phytin P values were used to derive phytic acid content by assuming 28.20% of

phosphorus is present in the molecule. Bran rich fraction (BRF) retained significant (P

≤ 0.05) phytin P and phytate content. As a result, semi refined flour contained lower

values for phytin P and phytic acid. This result correlate well with an earlier report on

pearl millet as well as wheat, stating that debranning to get refined flours considerably

reduced the phytate content, signifying the distribution of phytate in the outer layers

(Guansheng et al. 2005; Pawar et al. 2006). Pearl millet subjected to heat treatments

and germination respectively decreased Phytin P and phytate content (P ≤ 0.05).

The oxalate content was relatively low in pearl millet (31.6 and 36.0mg/g for K

and MRB). Heat treatments (boiling) and germination respectively further reduced

oxalate content to about 26% and 19% for K and MRB. Milling fractions such as SRF

and BRF retained significant (P ≤ 0.05) amounts of oxalate (ranging from 41.8 to

65.8mg/100g). Nevertheless, the values for the processed millet (except for BRF)

were below 50mg/100g, falling in the range of low oxalate foods. Similar amounts of

oxalates were found to occur widely in many vegetables and fruits which do not pose

a nutritional problem (Fasset, 1973; Ruth et al 2002).

Tannins are polyphenolic compounds which bind to proteins, carbohydrates

and minerals thereby reducing digestibility of these nutrients (Linda et al 2006). The

tannin content of pearl millet varied between the two varieties (K-0.23% and MRB-

0.21% tannic acid equivalents). However, these values were within the range reported

for millets (Pawar et al 1990; Ahmed et al 1996). The bran rich fraction of both

varieties retained most of the tannin content (about 0.32%). This increase can be


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attributed to concentration of tannins in the seed coat of the grain (Shivani et al 2004).

Tannin content significantly (P ≤ 0.05) reduced upon heat treatments but results

varied between the two varieties studied. Germination has been reported to reduce the

tannin content and improve in vitro digestibility of proteins in legumes (Maeda et al,

1991). In contrast, germination of pearl millet significantly (P ≤ 0.05) increased the

level of tannin in both varieties (from 0.21 to 0.28g/100 in MRB and 0.23 to

0.36g/100g in K).

The total dietary fiber content of the whole flour was higher in K variety

(13.3%) than MRB (11.91%). BRF had high total dietary fiber content (about

28.5g/100g). Heat treatments and germination did not did not bring about any

significant changes in the total dietary fiber content of pearl millet.


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Table – 4.8. Total and Soluble Amylose Content of Pearl Millet as Influenced by

Processing (g/100g)

Processing Soluble Amylose Total Amylose

K MRB K MRB

WF (raw) 1.06 b ± 0.07 1.72 c ± 0.03 3.47 d ± 0.05 2.89 a ± 0.07

SRF 2.15 e ± 0.05 1.60 c ± 0.10 4.29 f ± 0.10 4.81 f ± 0.08

BRF 1.60 c ± 0.12 1.15

b ± 0.07 2.47

a ± 0.02 3.83

d ± 0.03

Boiling 0.86 b ± 0.07 0.85

a ± 0.02 2.99

b ±

0.06 4.52

e ± 0.02

PC 0.53 a ± 0.02 0.85

a ± 0.04 2.51

a ± 0.03 4.93

f ± 0.14

Roasting 1.46 c ± 0.10 1.91

d ± 0.01 3.30

c ± 0.08 3.63

c ± 0.05

Germination 1.92 d ± 0.08 1.55 c ± 0.08 4.12 e ± 0.02 3.30 b ± 0.06

Values are mean ± SD (n = 4), Means with different superscripts (a, b, c, d, f) along the column

are significantly different (P ≤ 0.05), K – Kalukombu, MRB – Maharashtra Rabi Bajra, WF –

Whole flour, SRF – Semi refined flour, BRF – Bran rich fraction, PC – Pressure cooking.

Starch consists of two polydispersed α -D-glucan components, amylose and

amylopectin. Amylose is linear (α-D-[1 - 4]) or slightly branched and when dispersed

in water forms gels. The formation of a gel or paste, which is a determinant of food

texture, depends not only on the starch concentration but also the amount of amylose

and amylopectin leached from the granule and the heating conditions such as

temperature, time, heating velocity and shear stress (Miles et al 1985). Starch is

further classified based on the amylose content, as nonwaxy (17.0 to 31.9%), low

amylose (7.8 to 16.0%) and waxy type (0 to 3.5%) (Nakamura et al 1995). The total


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amylose content of defatted K (3.47g/100g) was higher than MRB (2.89g/100g)

(Table 4.8). Of this, 1.72% amylose was soluble in MRB while only 1.02% was

soluble in K. Based on the classification of starch as reported by Nakamura et al. the

starch in pearl millet can be classified as waxy. All the processing treatments

increased total amylose content in K variety with highest increase seen in pressure

cooked (4.93%) millet followed by boiled (4.52%) millet. However, in MRB, only

semi refined flour (4.29%) had the highest total amylose content followed by

germination (4.12%). All the processing treatments, except for wet heat treatment,

increased solubility of amylose content. Highest soluble amylose content was seen in

SRF (2.15%) of K variety followed by roasted MRB (1.91%).

Table 4.9. The Total Dietary Fiber Content and its Fractions of Pearl Millet as

Influenced by Processing (g/100g)

Processing Insoluble Dietary Fiber Soluble Dietary Fiber Total Dietary Fiber

K MRB K MRB K MRB

WF (raw) 12.6 a ± 1.6 10.9

a ± 1.7 0.70

a ± 0.0 1.05

a ± 0.1 13.3

a ± 1.8 11.9

a ± 1.8

SRF 8.6 a ± 0.2 9.2

a ± 0.2 0.65

a ± 0.2 1.5

a ± 0.3 9.2

a ± 0.2 10.6

a ± 0.4

BRF 27.1 b ± 4.9 27.0 b ± 7.8 0.90 a ± 0.1 2.1 b ± 0.5 28.0 b ± 5.0 29.1 b ± 7.8

Boiling 11.9 a ± 0.2 8.2 a ± 0.9 0.65 a ± 0.3 1.6 a ± 0.4 12.5 a ± 0.3 9.8 a ± 0.8

PC 12.0 a ± 0.6 9.9 a ± 0.3 0.63 a ± 0.2 1.2 a ± 0.2 12.6 a ± 0.7 11.1 a ± 0.2

Roasting 11.6 a ± 0.3 10.0 a ± 0.9 0.58 a ± 0.1 1.6 a ± 0.2 12.2 a ± 0.3 11.7 a ± 1.0

Germination 12.2 a ± 0.4 9.0 a ± 0.1 1.2 a ± 0.1 0.68 a ± 0.1 13.4 a ± 0.4 9.7 a ± 0.1

Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05), K

– Kalukombu, MRB – Maharashtra Rabi Bajra, WF – Whole flour, SRF – Semi refined flour,

BRF – Bran rich fraction, PC – Pressure cooking.


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The influence of common household processing methods on the dietary fiber

composition of pearl millet is depicted in Table 4.9. The total dietary fiber content of

the whole flour was higher in K variety (13.3%) than MRB (11.91%). The process of

partial removal of bran by sieving to obtain semi refined flour resulted in a significant

amount of dietary fiber (10.6% - MRB & 9.2% - K). Dehusking has been reported to

decrease dietary fiber content in pulses (Ramulu et al 1997). The bran rich fraction, a

byproduct of flour milling contained around 29% of total dietary fiber of which

around 1.5% was soluble and 27% was insoluble fraction. By virtue of its high fiber

content, the bran rich fraction can be used as a novel source of dietary fiber. Semi

refined flour of pearl millet can also be used in bakery products as it will contribute to

both the texture and fiber content of the products.

From the nutritional point of view, data on dietary fiber content of processed

millet is of importance, because millets are never eaten raw. In this study, wet and dry

heat treatment of the millets did not considerably change the insoluble and soluble

dietary fiber content. Although, boiling, pressure cooking and roasting increased the

SDF in MRB, it was statistically not significant. Changes in dietary fiber composition

of processed cereal and pulses have been reported where increase in TDF content

could be due to formation of resistant starch (Ramulu et al 1997).

Germination is an inexpensive technique for improving the nutritional quality of

millet seeds. The total dietary fiber content of germinated millet was 9.68% in MRB

and 13.4% in K variety. The results indicate that germination did not alter the total

dietary fiber and its fractions. Studies have indicated that germination has a

significant impact on the dietary fiber content. In legumes, germination increased the

dietary fiber content, while another study reported a decrease in dietary fiber content


Page 105

due to germination, which could be partly attributed to the conversion of complex

carbohydrates into simpler molecules by the action of hydrolyzing enzymes

(Mahadevamma et al 2003; Mathers 1989).

Table 4.10. Total Sugar Content of Pearl Millet as Influenced by Processing

Processing Total sugars (g/100g)

Kalukombu MRB

WF (Raw) 0.10 ab

± 0.00 0.06 a ± 0.00

Semi Refined Flour 0.11 abc

± 0.00 0.15 c ± 0.01

Bran Rich Fraction 0.19 d ± 0.00 0.21

d ± 0.02

Boiling 0.09 a ± 0.00 0.12 b ± 0.01

Pressure Cooking 0.14 c ± 0.02 0.12 b ± 0.00

Roasting 0.12 bc ± 0.00 0.13 bc ± 0.00

Germination 0.35 e ± 0.02 0.39 e ± 0.01

Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05);

MRB – Maharashtra Rabi Bajra,


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The total sugar content in the whole flour of K and MRB was 0.10% and

0.06% (Table 4.10). Overall, the milling fractions showed an increase in the total

sugar content for both varieties. Semi refining of MRB (0.15%) showed a substantial

increase in the total sugar content while; the same did not alter the sugar content of K

variety (0.11%). A three-fold increase in the total sugar content was noticed in the

germinated sample (about 0.37%) followed by 0.20% in BRF of both varieties.

Degradation of starch in grains during germination led to the increase in small dextrin

and fermentable sugar (Wijngaard et al 2005). Wet and heat treatments such as

boiling, pressure cooking and roasting respectively caused a marginal increase in the

total sugar content of both varieties compared to whole flour (raw).

Table 4.11. Total Soluble Protein Content of Pearl Millet as Influenced by

Processing

Processing Total soluble proteins (g/100g)

K MRB

WF (Raw) 2.63 b ± 0.18 3.63 c ± 0.30

Semi Refined Flour 2.48 b ± 0.22 3.75 c ± 0.41

Bran Rich Fraction 2.83 b ± 0.68 2.72

b ± 0.41

Boiling 0.92 a ± 0.10 2.04

a ± 0.35

Pressure Cooking 1.03 a ± 0.19 1.48

a ± 0.10

Roasting 1.29 a ± 0.12 1.51

a ± 0.39

Germination 2.76 b ± 0.46 3.68 c ± 0.34

Means followed by different letters (a, b, c) in the same column differ significantly (P

≤ 0.05); K – Kalukombu, MRB – Maharashtra Rabi Bajra.


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Soluble protein content of raw and processed pearl millet ranged from 0.92 to

2.83% in K variety and 1.48 to 3.75% in MRB (Table 4.11). Overall, both varieties

showed similar response to milling, heat treatments and germination. All the heat

treated samples (boiled, pressure cooked and roasted respectively) showed a

significant and sharp decline in the total soluble protein content however, semi

refining or germination did not alter the total soluble protein content in both varieties.

MWM – Molecular weight marker, WF – Whole flour, SRF – Semi refined flour, BRF – Bran

rich fraction.

Figure 4.1. Effect of Milling on Protein Profile of Pearl Millet


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MWM – Molecular weight marker, PC – Pressure cooking

Figure 4.2: Effect of Heat Treatment on Protein Profile of Pearl Millet

MWM – Molecular weight marker.

Figure 4.3: Effect of Germination on Protein Profile of Pearl Millet


Page 109

The SDS – PAGE was performed on the soluble protein extracts of two pearl

millet varieties (K and MRB) that were subjected to various processing treatments.

Both varieties showed similar electrophoretic patterns. The milling fractions were

classified as whole flour (WF), semi refined flour (SRF) and bran rich fraction (BRF).

The main protein bands at 38, 30 and 23 kDa along with some minor sub units of 66.2

and 45.0 kDa were found in the milling fractions of K and MRB (Fig. 4.1).

Protein bands of 66.2 and 45.0 kDa were prominent in all the heat treated millet

samples and low molecular weight protein bands were sparse in these samples.

Further wet heat treatment resulted in an enhanced appearance of 45, 42 and 36 kDa

in K and 35 to 38 kDa in MRB that was subjected to boiling (Fig. 4.2). Pearl millet

subjected to pressure cooking showed three characteristic bands of 40, 27 and 19kDa,

While, expression of only low molecular weight bands were found in MRB grains. In

roasted grains, the most prominent band was seen at 36 kDa. Further, expression of

low molecular weight bands was more prominent in K grains compared to MRB. In

general heat treatments caused shearing of protein, identified as a streak in the gel.

Upon germination a number of minor bands were concentrated between 34 –

14.4 and 45 – 35 kDa (Fig. 4.3). Biochemical as well as physical changes occur in

millets during germination. Functional proteins are synthesized in millet under a stress

circumstance, such as disease, physical or chemical stress. The stress plays an

important role in germination in the course of physiological response and functional

protein synthesis (Jingjun et al 2008).

Summing up, the results of the present investigation demonstrated a wide

variation in the nutrient composition of raw and processed pearl millet. MRB

contained higher protein and fat, while K variety exhibited higher ash reflecting its


Page 110

high mineral content. The bran rich fraction (BRF), a by product of milling, retained

significant amounts of fat, ash as well as antinutrients. Semi refining of pearl millet

flour displayed desirable nutritional qualities of both whole and refined flour. Heat

treatments and germination respectively reduced proteins, fat and ash content.

Functional properties varied with the processing methods with germination showing

higher bulk density. Variations in the total mineral content due to processing were

seen. For example, milling and heat treatment lowered iron, while the same was high

in the germinated millet. Calcium increased with the processing methods applied

while phosphorus reduced due to heat treatments and germination respectively.


Page 111

CHAPTER – 2

STUDIES ON ISOLATED STARCH FROM PEARL MILLET

Starch is the chief dietary source of carbohydrates and is the most abundant

storage polysaccharide in plants. It is present in high amounts in roots, tubers, cereal

grains and legumes (Eerlingen et al 1995). Starches have been used in the food

industry for variety of applications. The range of food products utilizing starch in one

form or another are soup, stew, gravy, pie filling, sauce or custard. Starch contributes

greatly to the textural properties of various foods and has many industrial applications

as a thickener, colloidal, stabilizer, gelling agent, bulking agent, water retention agent

and adhesive (Singh et al 2003).

Starch is a major component of pearl millet. In different pearl millet

genotypes the starch content of the grain varied from 62.8 to 70.5 % (Taylor 2004).

Attempts to isolate starch from pearl millet have been previously reported (Hadimani

et al 2001; Adelaide et al 1980; Hoover et al 1996). Most of the researchers used

random – mating bulk populations of pearl millet or cultivars grown in crop research

institutes for their research work. However, reports on isolated starch from local or

commercial varieties are scanty. Starch from the two commercially available pearl

millet varieties were isolated (K and MRB) and evaluate for its functional properties,

proximate composition, pasting and X-ray diffraction. The gelatinized pearl millet

starch was analyzed for nutritionally important starch fractions [rapidly digestible

starch (RDS), slowly digestible starch (SDS), and resistant starch (RS)] as described

by Englyst et al (1992).


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Table – 4.12. Chemical Composition of Corn and Pearl Millet Starches (g/100g)

Corn Kalukombu MRB

Yield† – 24.50

a ± 0.50 29.40

b ± 0.45

Moisture 9.62 a ± 0.14 12.81

b ± 0.20 12.47

b ± 0.20

Proteins£ 0.19 a ± 0.01 0.55

b ± 0.01 0.53

b ± 0.01

Fat 0.00 a ± 0.00 0.37 b ± 0.05 0.38 b ± 0.02

Ash 0.096 a ± 0.00 0.103 a ± 0.00 0.103 a ± 0.00

Total Amylose 16.8 c ± 0.06 14.0

a ± 0.10 15.0

b ± 0.16

† – The value represents the mean of three determinations, on whole flour basis

£ – Nitrogen x 6.25

Means followed by different letters (a, b, c) in the same column differ significantly

(P ≤ 0.05), MRB – Maharashtra rabi bajra.

Corn starch (control) K starch MRB starch

Figure 4.4. Pictures of Corn and Pearl Millet Starches


Page 113

The chemical composition of isolated starch from pearl millet is presented in

Table – 4. 12. The results revealed that MRB variety contained 29.4% starch which

was higher than K variety (24.5%) on the whole flour basis. However these values

were low when compared with the reported value (Wankhede et al 1990; Hoover et al

1996). The variations in the yield of starch from pearl millet may be due to isolation

and purification methods adopted by the researcher. The moisture content of pearl

millet starch was approximately 12% which was higher than corn starch (9.62%). The

amount and distribution of water within starch granules is important in relation to the

physical properties and chemical reaction of starch (Kokini et al 1992). The reported

moisture content of pearl millet starch was 10.18% while for cocoyam Starch; it

ranged from 9.4 to 17.3% which was considered to be within the acceptable range

(Wankhede et al 1990; Horsfall et al 2009). The protein content of pearl millet

starches (0.55 and 0.53% in K and MRB) was higher than corn starch (0.19%) and

were in the range reported by researchers (Wankhede et al 1990; Adelaide et al 1980).

The fat content of pearl millet starches was 0.37 and 0.38% for K and MRB. These

values were less than that reported (0.45 – 0.51%) (Hoover et al 1996). The amylose

content of the starch was approximately 14.5%. According to reported values (Badi

et al 1976) pearl millet starch contains 17% amylose.


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Table – 4.13a. Water Holding Capacity, Oil Holding Capacity and Bulk Density

of Pearl Millet and Corn Starches.

Isolated Starch WHC (g/g) OHC (g/g) Bulk Density (ml/g)

Corn (C) 0.41 a ± 0.01 1.90 c ± 0.08 1.85 a ± 0.05

Kalukombu 0.48 b ± 0.01 0.73

a ± 0.08 1.90

a ± 0.05

MRB 0.44 ab ± 0.03 1.27 b ± 0.09 1.90 a ± 0.05

Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05),

MRB – Maharashtra Rabi Bajra.

4.13b. Swelling Power and Solubility of Pearl Millet and Corn Starches (g/g).

Starch 55 oC 65 oC 75 oC 85 oC 95 oC

Corn

(Control)

SP 1.80 a ± 0.00 2.10

b ± 0.05 7.40

c ± 0.01 8.50

d ± 0.01 8.54

d ± 0.04

Solubility 0.001 a ± 0.0 0.029

e ± 0.0 0.009

b ± 0.0 0.018

c ± 0.0 0.024

d ± 0.0

K

SP 2.02 a ± 0.01 5.43 b ± 0.05 7.62 c ± 0.05 8.76 d ± 0.05 12.13 e ± 0.03

Solubility 0.001 a ± 0.0 0.035 c± 0.0 0.027 b± 0.0 0.015 b± 0.0 0.024 b± 0.0

MRB

SP 2.77 a ± 0.05 4.60

b ± 0.01 7.19

c ± 0.02 10.75

d ± 0.04 12.06

e ± 0.04

Solubility 0.001 a ± 0.0 0.053

d ± 0.0 0.048

e ± 0.0 0.018

b ± 0.0 0.025

c ± 0.0


(P ≤ 0.05), K – Kalukombu, MRB – Maharashtra rabi bajra, SP – Swelling power.


Page 115

K-Kalukombu, MRB- Maharashtra rabi bajra

Figure 4.5. Swelling Power and Solubility of Pearl Millet and Corn Starches

The ability to hold water is an important functional attribute of all flours and

starches used in food preparations such as custard, dough etc. The observed water

holding capacity (WHC) of the starches was lower than that reported for pearl millet

starch (Adelaide et al 1980). The ability of food materials to absorb water is

sometimes attributed to its proteins content (Kinsella 1976). The observed WHC of

starches studied cannot, however, be attributed to the protein content since pearl

millet starch in particular has low protein. Oil holding capacity (OHC) is useful in

structure interaction in food especially in flavor retention, improvement of palatability

and extension of shelf life particularly in bakery or meat products (Adebewale et al

2004). The range of OHC of the starch samples (0.73 – 1.90ml/g) showed that corn


Page 116

starch (1.90ml/g) had highest OHC followed by MRB (1.27ml/g) and K (0.73ml/g)

(Table 4.13a). The higher OHC of the millet flour could be due to its higher fat

contents, which can entrap more oil. Basically, the mechanism of OAC is mainly due

to the physical entrapment of oil by capillary attraction (Kinsella 1976).

Swelling and solubility of starches provides indication of noncovalent bonding

between molecules within starch molecule (Horsfall et al 2009). Swelling and

solubility of pearl millet and corn starches were determined over a range of

temperatures (55 – 95oC). Swelling power of pearl millet and corn starches (Table

4.13b & Fig 4.5) showed the amount of water absorbed significantly (P ≤ 0.05)

increased with increase in temperature (55 – 95oC). Swelling behavior of starch is

mainly due to swelling of amylopectin (Tsai et al 1997). Starch from K and MRB had

significantly (P ≤ 0.05) higher swelling power than corn starch. The swelling power

has been shown to be influenced by the amylose/amylopectin ratio and by the

characteristics of amylose and amylopectin in terms of molecular weight distribution,

degree of branching, length of branches and conformation of the molecules (Hoover

et al 2002).

The solubility pattern was determined in conjunction with swelling power (Table

4.13b & Fig 4.5). Solubility patterns did not basically follow swelling patterns. Pearl

millet and corn starches had higher solubility at 65oC. From 65 to 95

oC, all the starch

samples were less soluble in water. As the swelling of starch increased with increase

in temperature, its solubility decreased. Similar trend was also seen in pearl millet raw

and processed flours.


Page 117


Page 118

Figure 4.6. X – Ray Deffractograms of Pearl Millet and Corn Starches and Pearl

Millet Flours

Starch is a semi crystalline polymer with low and imperfect crystallinity. The

crystal structures in native starches are formed by packing of hexagonal arrays of

amylopectin in helical coils. The amylopectin side chains, organized in double helices

and constituting the crystalline fraction of starch, are considered as mesogens,

attached to the backbone through amorphous and flexible spacer units. The length of

these amylopectin double helices are related to the crystalline morphology of starch

(short double helices related to A – type and long double helices to B – type) (Zobel

et al 1988; Amparo et al 2007). Native starch granules display quite a complex

structure with several levels of organization. Starch constituting two main polymers

(essentially linear amylose and branched amylopectin) is distributed in amorphous


Page 119

and semi crystalline concentric shells. (Amparo et al 2007). Heat and humidity

involved in many processing conditions results in the disruption of starch’s structure,

a phenomenon known as gelatinization. Gelatinization involves loss of granular and

crystalline structures by heating with water and often including other plasticizers or

modifying polymers (Vermeylen et al 2006). Information regarding starch granule’s

crystalline properties can be acquired by X – ray diffraction studies by exposing the

starch samples to X – ray beam. Starch can be classified as A, B and C forms. In the

native granular forms, the A pattern is associated mainly with cereal starches, while

the B form is usually obtained from tuber starches. The C pattern is a mixture of both

A and B types, but also occurs naturally, e.g. smooth-seeded pea starch and various

bean starches (Norman et al 1998). The X – ray diffraction patterns of corn and

isolated pearl millet starches as well as whole flour of pearl millet are presented in

Fig. 4.6. The results revealed that pearl millet starches showed X – ray patterns

similar to corn starch (control). Corn starch exhibited sharper peaks at 2θ values of

14.69, 18.08 and 22.86 with an unresolved doublet at 2θ of 17.02. Similarly, K variety

showed peaks at 2θ values 14.92, 17.8 and 23.26 while MRB showed peaks at 15.3,

18.44 and 23.2. The diffraction pattern of corn and pearl millet starches was similar

to any other unprocessed cereal starch indicating its semi crystalline nature. The

whole flour of K exhibited diffraction patterns similar to its isolated starch but for a

slight shift in the 2θ values (from 15.36 to 14.92, 17.48 to 16.94 and 18.2 to 17.8

respectively). Whole flour and isolated starch from MRB exhibited similar diffraction

patters. However, the intensity of the peaks for the starch was comparatively higher

than that of the respective whole flour samples. The X – ray diffractograms mainly

represent the type of the starch present in the sample. Apart from starch which is the


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major component of the whole flour, it also contains other components such as

proteins, dietary fiber, fat etc. The presence of these components may slightly

interfere with the diffraction pattern of the samples. Hence, slightly sharper peaks for

the starch samples may be expected. It was observed from the diffractograms that

these samples exhibited ‘A’ type diffraction pattern similar to any other cereal

starches (Norman et al 1998). The sharp peaks in an X – ray diffractogram are

directly correlated to crystalline region and the diffused peaks to amorphous region of

the samples (Usha et al 2011). In the present study, all the three starches exhibited

semi – crystalline type.

Table – 4.14. Nutritionally Important Starch Fractions of Corn and Pearl Millet

Starches (g/100g).

Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05).

K – Kalukombu, MRB – Maharashtra rabi bajra, TS – total starch, RDS – rapidly digestible

starch, SDS – slowly digestible starch, RS – resistant starch, RAG – readily available glucose.

Starch TS RDS SDS RS SDI RAG

Corn (C) 20.2 a ± 0.25 10.2

a ± 0.27 7.2

a ± 0.35 2.8

b ± 0.52 50

a ± 1.00 11.3

a ± 0.30

K 22.5 b ± 0.80 11.3

b ± 0.31 9.0

b ± 0.29 2.2

ab ± 0.23 50

a ± 0.45 12.5

b ± 0.34

MRB 21.5 ab

± 0.00 12.2 c ± 0.18 7.9

a ± 0.34 1.4

a ± 0.19 57

b ± 0.84 13.6

c ± 0.20


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Nutritionally important starch fractions of starch from two pearl millet

varieties and corn (control) is presented in table 4.14. Gelatinization is an important

step in starch processing; hence all the starch samples were gelatinized prior to

analysis (sample to water ratio of 1:4) and expressed on an as eaten basis. Starch is

the main carbohydrate in human nutrition and is chiefly divided into rapidly digestible

starch (RDS), slowly digestible starch (SDS), and resistant starch (RS). RDS and SDS

in pearl millet starches were higher than corn starch (control). However RS content

was higher in corn (2.8) and K (2.2) while lower in MRB (1.4). The lower RS content

of these gelatinized starches was apparently due to the elimination of structural

obstruction to amylase hydrolysis during the process of starch isolation (Perera et al

2010). Also during the process of gelatinization which involves uptake of water and

heat by starch granules lead to the disruption of the crystalline structure and

consequently increased accessibility of glucose chains to amylolytic enzymes

(Sadequr et al 2007). The pearl millet starches had similar total starch (TS) content

which was higher than corn starch.

A measure of the relative rate of starch digestion is given by starch digestion

index (SDI). In the present investigation, SDI ranged from 50 (K and corn) to 57

(MRB). Similar values were reported for freshly cooked spaghetti (52), millet (55)

and lentils (44). The rate of starch digestion was comparatively low in the starch

isolated from pearl millet and corn (control) may be due to the fact that the physical

form of these starches which are millet based possibly render starch partly

inaccessible to the digestive enzymes (Englyst et al, 1992). The simple in vitro

measurement of RAG and SAG is of physiologic relevance and could serve as a tool

for investigating the importance of the amount, type, and form of dietary


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carbohydrates for health (Klaus et al, 1999). RAG values are those which represent

the amount of glucose that can be expected to be rapidly available for absorption after

a meal. It is a better indicator of blood glucose and insulin response as it includes

RDS and FG (Free glucose). RAG ranged from 11.3 (Corn) to 13.6 (MRB). Similar

RAG values were reported for instant potatoes, millet and spaghetti (approx. 13%)

(Englyst et al 1992). Low RAG values could be attributed to the fact that time for

gelatinization was too short for complete gelatinization of starch molecules and due to

the dense matrix which hindered enzymatic hydrolysis of starch.

In conclusion, the yield of starch from pearl millet was lower (about 26.5%)

than that reported (Wankhede et al 1997; Hoover et al 1996). Water and oil holding

capacity of pearl millet starched were higher that corn starch. Swelling power of corn

and pearl millet starches increased with increase in the temperature (55 to 95 oC).

However solubility patterns did not follow the trend set by swelling power. As the

swelling power increased with temperature, its solubility decreased. X – Ray

diffraction of corn and pearl millet starches exhibited semi crystalline structure.

Relatively sharper peaks exhibited in the starch compared to respective whole flour

suggested the interference of other components such as proteins, fat etc. An invitro

method for measuring nutritionally important starch fraction provided a means for

predicting the rate and extent of digestion in the human digestion. Although RDS and

SDS were lower than corn starch, RS and TS were relatively higher.


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CHAPTER – 3

ANTIOXIDANT COMPONENTS AND ACTIVITY OF PEARL MILLET AS

INFLUENC ED BY PROCESSING

The term “phytochemicals” or “plant chemicals” refers to every naturally

occurring chemical substance present in plants, which also has a potential for

antioxidant activity. Antioxidants play an important role in the body defense system

against reactive oxygen species (ROS), which are the harmful byproducts generated

during normal cell aerobic respiration (Boxin et al 2002). In foods, antioxidants

prevent undesirable changes in flavor and nutritional quality of a product (Zielinski et

al 2000). Several methods have been developed to measure “Antioxidant activity”.

Commonly used assays are reducing power assay (RPA), ferric reducing antioxidant

power (FRAP) and DPPH free radical scavenging activity. There are two basic

categories of antioxidants, namely, natural and synthetic. Examples of nature

antioxidants are phenolic compounds (tocopherols, flavonoids, and phenolic acids),

nitrogen compounds (alkaloids, chlorophyll derivatives, amino acids, and amines),

carotenoids and ascorbic acid. Butylated hydroxyanisole (BHA) and butylated

hydroxytoluene (BHT) are examples of commonly used synthetic antioxidants that

have been in use since the beginning of this century. Restrictions on the use of these

compounds, however, are being imposed because of their carcinogenicity (Velioglu et

al 1998; Hudson 1990). Thus, natural antioxidants have gained considerable interest

in recent years.

Cereals and millets are the most commonly consumed food items in India.

They contain wide range of phenolics which are good sources of natural antioxidants.

Studies report that methanolic extracts from red sorghum showed higher antioxidant


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activity and contain higher polyphenolic levels compared to rice, foxtail millet,

prosomillet and barley (Youngmin et al 2007). Bran, a byproduct of milling has

antioxidant potential due to phenolic acids such as p- coumaric acid and vanillic acids

that are concentrated in the bran portion of cereal kernels. Antioxidant activity of five

bran extracts exhibited appreciable levels of total phenolics, flavonoids and DPPH

radical scavenging activities (Shahid et al 2007). Processing such as soaking and

roasting have been shown to influence total phenolic, flavonoid and antioxidant

contents in selected dry beans. Raw kodo millet and finger millet have higher DPPH

radical scavenging activities. However cooking of these millets by roasting or boiling

reduced their antioxidant activity (Prashant et al 2005).

Millets contain phytic acid, tannins, phenols which can contribute to

antioxidant activity important in health, ageing and metabolic diseases. Pearl millet

(Pennisetum typhoideum) is the most widely grown type of millet. Nutritionally, pearl

millet is superior to major cereals with reference to energy value, high quality

proteins, fat and minerals such as calcium, iron, zinc. Besides, it is also a rich source

of dietary fiber and micro nutrients (Anu Sehgal et al 2006; Malik et al 2002). While,

extensive information is available on proximate composition and mineral

accessibility, information on antioxidant activity and its influence on processing in

pearl millet are scanty. Research on the effect of processing on retention of bioactive

components with potential antioxidant activity is very important.

The objective of this investigation was to evaluate the effect of various

processing methods (milling, heat treatments and germination respectively) on

antioxidant components as well as antioxidant activities of pearl millet extracts. The

methanolic extracts of raw and processed pearl millet were analyzed for DPPH free


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radical scavenging activity; reducing power assay (RPA) and ferric reducing

antioxidant power (FRAP) assays respectively. The samples were also evaluated for

tannin, phytic acid and flavonoid content and were correlated with the antioxidant

activity assayed using three methods.

Table 4.15. Yield of Methanolic Extracts from Pearl Millet as Influenced by

Processing (g/100g)

Processing Kalukombu MRB

Whole flour (Raw) 5.8 cd ± 1.20 4.4 bc ± 0.87

Semi refined flour 4.8 bc ± 0.30 3.7 abc ± 0.26

Bran rich fraction 2.1 a ± 0.05 3.2

ab ± 0.15

Boiling 2.4 ab

± 0.38 2.2 ab

± 0.14

Pressure cooking 2.2 a ± 0.10 1.8

a ± 0.04

Roasting 3.0 ab

± 0.03 2.3 ab

± 0.04

Germination 7.7 d ± 0.12 6.1 c ± 0.34


are significantly different (P ≤ 0.05), MRB - Maharashtra Rabi Bajra.


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Antioxidants are difficult to extract due to differences in the active

compounds. A wide variation is seen in detecting antioxidant components due to

differences in the polarity of the extracting solvents. Methanol is a relatively polar

organic solvent and appears to be efficient in extracting compounds such as phenolics,

flavonoids, and other polar material from millets (Florence et al 2010; Singh et al

2002). Methanol was therefore selected as an extracting solvent in the present

investigation. Table 4.15 exhibits the yield of methanolic extracts obtained from the

raw and processed two pearl millet varieties. The K variety (5.8g/100g) had higher

yield than MRB (4.4g/100g). Wide variations in the yield as a result of processing

were seen. Lower yields were seen in the millet subjected to heat treatments (boiling,

pressure cooking, roasting) as well as in the bran rich fraction while, the processes of

germination facilitated maximum extraction in both varieties; however this increase

was not statistically significant.


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Table 4.16. Effect of Processing on Antioxidant Components of Pearl millet.

Processing

treatments

Tannins (g/100g)† Phytic acid (g/100g) Flavonoids (mg/g)

£

K MRB K MRB K MRB

WF (Raw) 0.23 c ± 0.01 0.21

a ± 0.02 0.78

c ± 0.02 0.57

cd ± 0.07

0.27

ab ± 0.04 0.21

a ± 0.02

SRF 0.21 b ± 0.01 0.19 a ± 0.01 0.66 b ± 0.06 0.33 ab ± 0.09 0.20 a ± 0.07 0.18 a ± 0.02

BRF 0.31 d ± 0.01 0.32

b ± 0.01 0.99

d ± 0.06 0.61

d ± 0.10 0.19

a ± 0.01 0.18

a ± 0.00

Bo 0.18 a ± 0.01 0.19

a ± 0.01 0.57

b ± 0.11 0.39

ab ± 0.04

0.32

abc ± 0.1 0.13

a ± 0.00

PC 0.18 a ± 0.01 0.22 a ± 0.02 0.58 b ± 0.04 0.60 d ± 0.06 0.36 bc ± 0.06 0.13 a ± 0.01

Ro 0.20 b ± 0.00 0.23

a ± 0.03 0.43

a ± 0.06 0.45

bc ± 0.11

0.44

c ± 0.10 0.27

a ± 0.07

G 0.36 e ± 0.01 0.28

a ± 0.01 0.37

a ± 0.07 0.26

a ± 0.01 0.17

a ± 0.02 0.10

a ± 0.02

† - g tannic acid equivalents/100 of dry flour

£ - mg rutin equivalents/g of extract.


are significantly different (P ≤ 0.05), K – Kalukombu, MRB – Maharashtra Rabi Bajra, WF –

Whole flour, SRF – Semi refined flour, BRF – Bran rich fraction, Bo – boiling, PC – Pressure

cooking, Ro – roasting, G – germination.


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Millets contain phytates, phenols, tannins, trypsin inhibitors and dietary fiber

which act as ‘antinutrients’ by chelating minerals. Tannins are naturally occurring

polyphenolic compounds linked to reduce protein digestibility by forming complexes

with proteins and inhibiting enzymes (Aganga et al 2001). It is now established that

phytates, phenols and tannins present in cereals are also good sources of natural

antioxidants important in health, aging and metabolic diseases (Krings et al 2000).

Phytic acid occurring in the grains acts as an antioxidant by the formation of chelates

with prooxidant transition metals. Although, phytic acid is generally regarded as an

antinutrient due to its mineral binding activity it is known to reduce the risk for colon

and breast cancer in animals (Graf et al 1990). Table 4.16 exhibits tannin, phytic acid

and flavonoid content of raw and processed pearl millet. The tannin content of K and

MRB expressed as tannic acid equivalents was 23 and 21g/100g of dry flour. Semi

refining reduced the level of tannins in the SRF thus increasing its levels in BRF

suggesting its localization in the outer hulls of the grain. Millet subjected to various

heat treatments lead to considerable reduction in tannin levels only in the K variety.

On the other hand, the increase in the tannin content of the germinated flour extract in

both varieties was pronounced, however, statistically not significant for MRB variety.

The phytic acid content was highest in K (78g/100g) compared to MRB

(57g/100g). Semi refining significantly reduced the corresponding values to 66 and

33g/100g for K and MRB respectively. They were mainly found concentrated in the

bran rich fraction (99 and 61g/100g K and MRB respectively). Phytic acid content

significantly (P ≤ 0.05) decreased due to heat treatments though maximum reduction

was seen in the germinated millet.


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The flavonoid content of raw and processed millet extract were expressed as

mg rutin equivalents per gram of the extract (10mg/ml). The flavonoid content was

high in K (27mg/g) than MRB (21mg/g). The milling fractions (SRF and BRF)

irrespective of varietal differences, showed a reduction in the flavonoid content,

nonetheless, the decrease was not statistically significant. Unlike tannins and phytic

acid, the flavonoid levels considerably increased due to heat treatments (boiling,

pressure cooking, roasting) while, germination did not alter the flavonoid content of

pearl millet.


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Table 4.17. Effect of Processing on the Radical Scavenging Activity of Pearl

Millet Extracts by DPPH Method

Processing 200µg 400µg 600µg

K MRB K MRB K MRB

WF (Raw) 22 a12

± 7.2 31 ab1

± 5.7 37 b12

± 7.3 42 b1

± 7.9 42 b1

± 9.3 40 b1

± 7.7

SRF 16 a1

± 3.9 30 bc1

± 8.3 29 b1

± 9.3 41 de1

± 8.8 42 cd1

± 10.5 53 e2

± 3.6

BRF 19 a12

± 7.9 21 a1

± 2.5 31 c12

± 11.5 31 b1

± 1.3 38 d1

± 14.0 40 c1

± 2.9

Boiling 26 a2

± 7.9 26 a1

± 8.3 42 b2

± 11.8 41 b1

± 7.9 57 c23

± 8.6 45 b1

± 6.0

PC 24 a12

± 4.0 23 a1

± 6.7 41 b2

± 7.3 34 b1

± 9.9 57 c23

± 4.5 40 b1

± 0.6

Roasting 23 a12

± 4.3 29 a1

± 9.9 46 b2

± 4.1 45 b1

± 11.3 56 c3

± 3.8 61 c2

± 4.3

Germination 16 a12 ± 2.4 22 a1 ± 5.3 24 a1 ± 5.7 33 b1 ± 8.7 35 b1 ± 4.8 41 b1 ± 3.8

Concentration of the extracts – 10mg/ml, Values are mean ± SD (n = 4), Means with different

superscripts (a, b, c, d) along the row are significantly different (P ≤ 0.05), Values are mean ±

SD (n = 4), Means with different superscripts (1, 2, 3) along the column are significantly

different(P ≤ 0.05) , K - Kalukombu, MRB - Maharashtra Rabi Bajra, WF – Whole flour, SRF

– Semi refined flour, BRF – Bran rich fraction, PC – Pressure cooking.


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Bars with different superscripts (a, b, c, d) are significantly different (P ≤ 0.05), WF – whole

flour, SRF – semi refined flour, BRF – Bran rich fraction, Bo – boiling, PC – pressure


Figure – 4.7: Effect of Processing on the Radical Scavenging Activity of Pearl

Millet Extracts by DPPH Method

Table 4.17 and Figure 4.7 summarize data on DPPH radical scavenging

activity of raw and processed pearl millet. In DPPH assay, the color stable DPPH

radical is reduced in the presence of an antioxidant which donates hydrogen to non –

radical DPPH – H (Sanna et al 2006). DPPH free radical scavenging activity was

studied at three concentrations (200 µg, 400 µg and 600 µg). Radical scavenging

activity varied with the processing methods used and was concentration dependent.


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The greatest activity was obtained at a higher concentration of 600µg in the raw and

processed flour extracts. For example, the antioxidant activity of K and MRB which

was 22% and 31% at 200µg considerably increased to 42% and 40% respectively at

600µg. Heat treatments such as boiling; roasting and pressure cooking exhibited

significantly higher antioxidant activity as compared to the raw flour. Similar findings

were reported for little millet where roasting of the millet enhanced its radical

scavenging activity (95.5%), compared to germinated (91.7%) and steamed (93.4%)

millet (Pradeep et al 2011). In contrast, cooked peppers showed a marked reduction

in the radical scavenging activity when cooked for 30 minutes in boiling water. This

may be due to leaching of antioxidant compound from the pepper into cooking was

during the prolonged exposure to water and heat (Ai Mey Chuah et al 2008). It was

noteworthy that significantly high radical scavenging activity in heat treated millet

had the lowest yield, whilst, germinated millet extracts which showed lowest activity

had highest yield.


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Table 4.18. Effect of Processing on the Ferric Reducing Power of Pearl Millet

Extracts at Various Concentrations

Processing 200µg 400µg 600µg

K MRB K MRB K MRB

WF (Raw) 0.07 a12

± 0.01 0.06 a1

± 0.01 0.20 c23

± 0.01 0.15 b12

± 0.01 0.31 d1

± 0.03 0.32 d3

± 0.03

SRF 0.06 a1

± 0.02 0.06 a1

± 0.00 0.11 b1

± 0.03 0.13 b1

± 0.01 0.29 c1

± 0.07 0.27 c123

± 0.02

BRF 0.10 b2± 0.03 0.05 a1± 0.02 0.23 e3 ± 0.09 0.14 c12 ± 0.06 0.34 f2 ± 0.11 0.20 d1 ± 0.05

Boiling 0.10 a2

± 0.03 0.08 a1

± 0.01 0.19 b23

± 0.04 0.17 b2

± 0.01 0.47 d2

± 0.04 0.29 c23

± 0.03

PC 0.08 a12

± 0.00 0.06 a1

± 0.01 0.17 b2

± 0.02 0.14 b12

± 0.01 0.29 d1

± 0.03 0.23 c12

± 0.03

Roasting 0.09 a2± 0.01 0.07 a1± 0.01 0.21 c23 ± 0.00 0.16 b12 ± 0.02 0.39 e12 ± 0.09 0.28 d23 ± 0.01

G 0.07 a12

± 0.01 0.07 a1

± 0.02 0.16 b2

± 0.01 0.17 b2

± 0.03 0.29 c1

± 0.02 0. 30

c23 ± 0.02

Concentration of the extracts – 10mg/ml, Values are mean ± SD (n = 4), Means with different

superscripts (a, b, c, d) along the row are significantly different (P ≤ 0.05), Means with different

superscripts (1, 2, 3) along the column are significantly different (P ≤ 0.05), K – Kalukombu, MRB –

Maharashtra Rabi Bajra, WF – Whole flour, SRF – Semi refined flour, BRF – Bran rich fraction, PC –

Pressure cooking, G – germination.


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Different superscripts (a, b, c) on each bars are significantly (P ≤ 0.05) different (n = 6), WF

– whole flour, SRF – semi refined flour, BRF – bran rich fraction, Bo – boiling, PC – pressure


Figure – 4.8: Effect of Processing on the Ferric Reducing Power of Pearl Millet

Extracts at Various Concentrations

The ferric reducing power of raw and processed millet is presented in Table

4.18 and Fig 4.8. It was observed that the results followed a similar trend of DPPH

free radical scavenging activity. The reducing power assay of methanolic extracts of

the two pearl millet varieties differed between the processing treatments employed.

Raw and processed millet extracts exhibited lower reducing power at 200 µg,

nevertheless, it increased with the concentration (600µg). The reducing power of K

and MRB flour extracts at 200µg concentration were A700 = 0.07 and 0.06 respectively.

The corresponding values increased to A700 = 0.31 and 0.32 respectively at 600 µg. The


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respective bran rich fraction, roasted and boiled millet extracts of K variety exhibited

an increase in the absorbance (A700 = 0.34, 0.39 and 0.47, respectively) compared to

the raw millet extract (A700 = 0.31) while, processing did not alter the antioxidant

activity (reducing power) of MRB.

Table . 4.19. Effect of Processing on FRAP of Two Pearl Millet Varieties


Whole flour (Raw) 2.24 ab ± 0.57 1.85 ab ± 0.21

Semi refined flour 2.89 b

± 0.54 1.63 a ± 0.20

Bran rich fraction 2.08 ab

± 0.05 1.72 ab

± 0.09

Boiling 2.18 ab ± 0.03 1.99 ab ± 0.07

Pressure cooking 1.54 a ± 0.11 1.80

ab ± 0.00

Roasting 2.58 b

± 0.33 2.17 b

± 0.12

Germination 2.69 b ± 0.07 1.66 a ± 0.23


are significantly different (P ≤ 0.05), MRB - Maharashtra Rabi Bajra.


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Ferric reducing antioxidant power (FRAP) assay is a novel method for

assessing antioxidant power where the ferric reducing ability of sample extract is

tested. Ferric to ferrous ion reduction at low pH causes a colored ferrous-

tripyridyltriazine complex to form. FRAP values are obtained by comparing the

absorbance change at 593 nm in test reaction mixtures with those containing ferrous

ions in known concentration (Iris et al 1996). In this study, FRAP was calculated

using the equation Y = 0.2453x, where x is the OD of the sample. The ferric reducing

ability of the extracts was higher in K (2.24) followed by MRB (1.85) (Table 4.19).

Pressure cooked K variety and germinated MRB exhibited lowest activity, although

the decrease was not statistically significant. Overall, the processing methods

employed in this study did not cause any significant changes in the activity (FRAP) of

the millet.

Table 4.20. Correlations of Yield and Antioxidant Components with Antioxidant

Activity of Two Pearl Millet Varieties

Pearl millet Yield Phytic acid Tannins Flavonoids

Kalukombu

DPPH – 0.629** – 0.130 – 0.557** 0.712**

Reducing power – 0.361 0.222 – 0.100 0.456*

FRAP 0.478* – 0.148 0.165 – 0.078

MRB

DPPH – 0.317 – 0.279 – 0.121 – 0. 282

Reducing power – 0.317 – 0.273 – 0.110 – 0.282

FRAP – 0.322 0.276 – 0.141 0.181

* – correlation is significant at the 0.05 level (2 tailed); **– correlation is significant at the

0.01 level (2 tailed), MRB – Maharashtra rabi bajra, FRAP – Ferric reducing antioxidant

power.


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The relationship of antioxidant activity with antioxidant components as well as

the yield of methanolic extracts of raw and processed pearl millet is presented in

Table 4.20. There was variation in the antioxidant activity analyzed by different

assays and antioxidant components in K and MRB varieties. The results indicated

significant negative correlations between methanolic extract (r = – 0.629, P ≤ 0.01) as

well as tannin content (r = - 0.557, P ≤ 0.01) while, a positive relationship between

flavonoid content (r = 0.712, P ≤ 0.01) with DPPH free radical scavenging activity.

There was a strong positive relationship between reducing power and flavonoid

content (r = 0.456, P ≤ 0.05) and FRAP with methanolic extracts (r = 0.478, P ≤

0.05). These results suggest that the DPPH radical scavenging activity and reducing

power assay in K variety was largely due to the presence of flavonoids. However, in

MRB, antioxidant components such as phytic acid, tannin and flavonoids were poorly

correlated with antioxidant activity as determined by three methods suggesting that

these components did not contribute to the antioxidant activity of MRB variety.

In conclusion the antioxidant activity of pearl millet varied with the processing

methods and between the two varieties (K and MRB) studied. K variety had higher

content of antioxidant components reflecting its higher antioxidant capacity,

compared to MRB. BRF showed high antioxidant activity in terms of RPA which was

due to tannin, phytic acid and flavonoid levels. The millet subjected to various heat

treatments exhibited higher antioxidant activity (DPPH scavenging activity and RPA)

mainly due to flavonoid content. It was worthy of notice that significantly high radical

scavenging activity in heat treated millet had the lowest yield, whilst germinated

millet which showed lowest activity had highest yield.


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CHAPTE R– 4

STUDIES ON NUTRIENT DIGESTIBILITY (IN-VITRO) OF

PEARL MIL LET

Pearl millet, a lesser known and underutilized crop can be grown at low

maintenance cost, is relatively a cheaper source of nutrients and staple for population

below poverty line for economic reasons. It has the distinct advantage of being a

drought-resistant crop and hence acts as a principle source of energy, protein, fat and

minerals for poor people living in these regions. However, it has some limitations, due

to the presence of antinutritional factors such as phytate, tannins or dietary fiber.

These compounds are known to interfere with mineral bioavailability, carbohydrate

and protein digestibility (Fasasi, 2009; Anu Sehgal et al 2006; Malik et al 2002).

The bioavailability of minerals from foods is defined as the proportion of the

minerals that can be absorbed and utilized within the body (Lestienne et al 2005).

Poor absorption of minerals leads to mineral deficiency resulting in conditions like

anemia. The high prevalence of iron deficiencies in developing countries has several

adverse effects on the population particularly on women and children (Zimmermann

et al 2007).

Carbohydrate digestibility in small intestine is influenced by the food form

(physical form, particle size), type of preparation (cooking method and processing),

type of starch (amylose or amylopectin) and presence of antinutrients, transit time,

and amount of fiber, fat, and proteins (Julia et al 2007). For nutritional purposes,

Englyst and Cummings (1993) classified the starch in foods as rapidly-digestible

starch (RDS), slowly-digestible starch (SDS) and resistant starch (RS). RDS causes a

rapid increase in blood glucose level after ingestion; SDS is digested slowly but


Page 139

completely in the human small intestine and RS is a portion of starch that cannot be

digested in the small intestine, but may be fermented in the large intestine (Englyst et

al 1992).

Protein digestibility is essentially a measure of the susceptibility of protein to

proteolysis. A protein with high digestibility is potentially of better nutritional value

than one with low digestibility because it provides more amino acids for absorption

on proteolysis. Exogenous (interaction of proteins with non-protein components like

polyphenols, non-starch polysaccharides, starch, tannins, dietary fiber, phytates and

lipids.) and endogenous factors (changes within the proteins themselves) contribute to

poor digestibility of proteins. During the process of milling and cooking, proteins

interact with non-protein components and the proteins themselves thereby affecting

their digestibility (Duodu et al 2003). Studies indicate that dietary fiber and tannins

contribute to lower nutritional value of dietary proteins with soluble dietary fiber

playing a major role in reducing its in vitro digestibility. In beans, soluble dietary

fiber plays a more important role than insoluble dietary fiber in reducing protein

digestibility (Joe Hughes, 1996). The purpose of the present study was to analyze

mineral bioaccessibility, nutritionally important starch fractions and invitro protein

digestibility of two pearl millet varieties as influenced by processing.


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Table – 4. 21. In-Vitro Bioaccessible Iron Content of Pearl Millet as Influenced

by Processing


Mg/100g % Mg/100g %

Whole Flour 0.16 a ± 0.03 3 0.44 c ± 0.07 6

SRF 0.20 ab

± 0.05 4 0.48

c ± 0.05 7

BRF 0.16 a ± 0.01 4 0.20 a ±0.01 4

Boiling 0.24 b ± 0.02 8 0.36 b ± 0.03 5

PC 0.33 c ± 0.03 10 0.33

b ± 0.02 5

Roasting 0.33 c ± 0.02 10 0.30

b ± 0.05 7

Germination 0.21 b ± 0.03 3 0.46 c ± 0.05 10


are significantly different (P ≤ 0.05), MRB – Maharashtra Rabi Bajra, SRF – semi refined

flour, BRF – bran rich fraction, PC – pressure cooking.

Table 4.21 represents data on bioaccessible iron content of pearl millet and its

impact on processing. The bioaccessible iron content of K was 0.16 mg/100g while

that of MRB was 0.44 mg/100g. Milling (SRF and BRF) did not alter the

bioaccessible iron content of pearl millet, except for bran rich fraction (BRF) of

MRB, where a two fold decrease was observed. On the other hand, heat treatments

enhanced iron bioaccessibility which was evident only in K variety. The bioaccessible


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iron content of K (0.16mg/100g) was increased to 0.24, 0.33 and 0.33 due to boiling,

pressure cooking and roasting respectively, while germination caused a minimal

increase of 0.21mg/100g. Although, bioaccessible iron content in MRB

(0.44mg/100g) was the highest, it subsequently decreased as a result of processing

with lowest decrease in the bran rich fraction followed by those subjected to heat

treatments.

Table – 4.22. In Vitro Bioaccessible Calcium Content of Processed Pearl Millet


Mg/100g % Mg/100g %

Whole Flour 30.1 b ± 0.37 67 34.6

c ± 2.41 78

SRF 22.4 a ± 3.64 44 26.1

b ± 2.47 49

BRF 20.8 a ± 1.12 34 15.7 a ± 1.11 18

Boiling 34.5 c ± 2.99 66 34.5

c ± 1.56 65

PC 30. 0

b ± 1.61 64 39.5

c ± 4.89 75

Roasting 35.9 c ± 2.99 72 24.8 b ± 3.22 63

Germination 35.7 c ± 2.51 66 38.0 c ± 3.37 71


are significantly different (P ≤ 0.05), MRB – Maharashtra Rabi Bajra, SRF – semi refined

flour, BRF – bran rich fraction, PC – pressure cooking


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The bioaccessible calcium content of K and MRB was 30.1 and 34.5mg/100g

respectively (Table 4.22). K variety subjected to heat treatments such as boiling or

roasting increased the bioaccessible calcium content to 34.5 and 35.9 mg/100g

respectively. Germination also brought about a similar increase in the calcium

bioaccessibility (35.7mg/100g) of K variety. However, in case of MRB, neither of the

processing treatments caused any improvement in the calcium bioaccessibility.

Further, significant (P ≤ 0.05) decrease in the bioaccessible calcium of BRF and

roasted millet was observed. Similar to iron bioaccessibility, processing did not

enhance bioaccessible calcium content of MRB. Cooking is reported to modify seed

composition and lowering of antinutritional factors in turn influencing dialysability of

iron and calcium. (Sreeramaiah et al 2007). This was evident in case of calcium

bioaccessibility studied in both varieties. Calcium in foods exists mainly as complexes

with other factors (phytates, oxalates, fibre, lactate, fatty acids) from which the

calcium must be released to be absorbed and heat treatments aided this process.

Cooking effectively improved bioaccessible calcium while the same was less effective

in improving bioaccessible iron content suggesting that calcium and iron combined in

a meal may decrease iron bioaccessibility.


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Table 4.23. Effect of Processing on Bioaccessible Iron and Calcium as Influenced

by Tap / De – Mineralized Water (mg/100g)

Processing Bioaccessible Iron Bioaccessible Calcium

TW DMW TW DMW

Kalukombu

Boiling 0.25 a ± 0.01 (7) 0.24

a ± 0.02 (8) 35.5

a ± 2.61 (67) 35.9

a ± 2.99 (66)

PC 0.35 a ± 0.02 (8) 0.33

a ± 0.03 (10) 32.7

a ± 2.41 (70) 30.0

a ± 1.61 (64)

G 0.25 a ± 0.03 (3) 0.21

a ± 0.03 (3) 35.9

a ± 13.68 (66) 35.7

a ± 2.51 (66)

MRB

Boiling 0.36 a ± 0.03 (6) 0.37 a ± 0.01 (5) 36.7 a ± 2.63 (69) 34.5 a ± 1.56 (65)

PC 0.33 a ± 0.02 (4) 0.35 a ± 0.04 (5) 36.6 a ± 4.02 (70) 39.5 a ± 4.89 (75)

G 0.46 a ± 0.05 (8) 0.47 a ± 0.01 (10) 40.8 a ± 4.93 (76) 38.0 a ± 3.37 (71)

Values are mean ± SD (n = 4), means with different superscripts (a, b,) along the row are

significantly (P ≤ 0.05) different, values in the parenthesis are % bioaccessible iron/calcium, MRB

– Maharashtra rabi bajra, TW – tap water, DMW – demineralized water, PC – Pressure cooking, G

– Germination.

Studies have report that contamination of iron originating from milling

equipment (mills equipped with iron-containing grindstones) led to a considerable

increase in bioaccessible iron, hence extrinsic iron supplied to food products by the

milling equipment could play a role in iron intake in developing countries (Valerie et

al 2011). Cooking water often contributes to mineral contamination influencing its

bioaccessibility. In view of this, tap water (previously passed through a water purifier)


Page 144

and de – mineralized water was used in processing treatments like boiling, pressure

cooking and germination respectively to see its effect on bioaccessible iron and

calcium content (Table 4.23). Although iron and calcium bioaccessibility of millet

processed using tap water was higher than de-mineralized water, the difference was

not significant.

Table – 4.24. Molar Ratios of Pearl Millet as Influenced by Processing

Processing [Phytate]/[Calcium]

1 [Phytate]/[Iron]

2 [Calcium]/[Phytate]

3 [Oxalate]/[Calcium]

4

K MRB K MRB K MRB K MRB

WF (Raw) 1.03 0.78 11.77 6.84 0.97 1.28 0.25 0.22

SRF 0.79 0.38 12.32 4.34 1.27 2.63 0.28 0.25

BRF 0.97 0.43 21.38 9.93 1.03 2.31 0.34 0.22

Boiling 0.64 0.65 15.20 7.30 1.57 1.55 0.15 0.13

PC 0.75 0.68 15.02 6.75 1.33 1.48 0.24 0.19

Roasting 0.55 0.70 11.40 9.60 1.82 1.43 0.23 0.18

Germination 0.75 0.42 8.40 6.90 1.33 2.40 0.16 0.10

1 Recommended critical value of [Phytate]/[Calcium] is 0.24, (Morris et al 1985)

2 Recommended critical value for [Phytate]/[Iron] is 1, (Hallberg et al 1989)

3 Recommended critical value for [Calcium]/[Phytate] is 6.1, (Oladimeji et al 2000)

4 Recommended critical value for [Oxalate]/[Calcium] is 1.0, (Davis, 1979)

K – Kalukombu, MRB – Maharashtra Rabi Bajra, WF – Whole flour, SRF – semi refined

flour, BRF – bran rich fraction, PC – pressure cooking.


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The bioavailability of minerals depends on the amount of antinutrients and the

ratio of antinutrients/minerals. These ratios are of significance when they are greater

than the recommended critical values. In such cases antinutrients (phytates and

oxalates) have a potential to complex with minerals (calcium/iron) thus impairing its

absorption. The molar rations for [Phytate/Calcium], [Phytate/Iron],

[Calcium]/[Phytate] and [Oxalate]/[Calcium] of raw and processed millet were

calculated to study the effect of oxalate and phytate contents on the bioaccessibility of

calcium and iron (Table 4.24). The phytate/calcium and phytate/iron molar ratios have

to be lower than 0.24 and 1 respectively (Morris et al 1985; Hallberg et al 1989).

Although, K and MRB exhibited molar ratios for phytate/calcium and phytate/iron

above the reference value, it decreased with the processing.

Furthermore, [Calcium]/[Phytate] and [Oxalate]/[Calcium] molar ratios of raw

and processed millet varieties were well below the recommended critical values of 1

and 6.1 respectively (Davis 1979; Oladimeji et al 2000). Oxalate forms insoluble

calcium salt with a 1:1 molar stoichiometry in the intestine thus, rendering calcium

unavailable for absorption. In view of this, the importance of the oxalate content in

limiting total dietary Calcium availability is of significance only when the calculated

molar ratios are greater than the recommended critical values. Since under these

circumstances the oxalate has the potential to complex not only the Calcium contained

in the plant but also that derived from other food sources (Davies 1979).


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Table – 4.25. Nutritionally Important Starch Fractions of Pearl Millet as

Influenced by Processing

Varieties Processing

Treatments

Dry Matter

(%)

Starch Fractions (g/100g as-eaten basis)

RDS SDS RS TS

K WF (Raw) 86.8 b ± 0.20 10.2 a ± 0.3 6.0 a ± 0.12 5.1 b ± 0.81 21.3 a ± 0.69

SRF 87.1 b ± 0.13 13.3

b ± 0.6 9.0

b ± 0.68 8.5

c ± 1.27 30.9

b ± 0.35

Boiling 83.9 b ± 1.11 16.9

d ± 0.2 15.7

d ± 0.29 3.3

ab ± 0.73 35.9

d ± 0.75

PC 84.7 b ± 0.97 14.0

b± 0.4 12.5

c ± 0.41 3.7

ab ± 0.85 30.1

b ± 0.51

Roasting 86.6 b ± 0.43 15.2

c ± 0.3 12.7

c ± 0.32 1.8

a ± 0.17 29.7

b ± 0.55

Germination 71.8 a ± 2.42 17.2

d ± 0.6 13.6

c ± 0.43 2.5

a ± 0.11 33.4

c ± 1.01

MRB WF (Raw) 85.9 b ± 0.11 11.4

a ± 0.6 7.6

a ± 0.48 4.0

b ± 0.90 23.0

a ± 0.35

SRF 86.3 b ± 0.30 12.7

b ± 0.4 7.7

a ± 0.80 10.3

c ± 0.47 30.7

b ± 0.74

Boiling 85.2 b ± 1.80 18.9

c ± 0.1 14.4

c ± 0.26 3.6

ab ± 0.37 36.3

c ± 0.58

PC 85.4 b ± 0.97 11.0

a ± 0.3 9.9

b ± 0.18 3.5

ab ± 0.65 24.4

a ± 0.55

Roasting 85.3 b ± 0.27 17.4

c ± 1.1 15.3

d ± 0.85 1.7

a ± 0.57 35.

0

c ± 0.38

Germination 74.4 a ± 2.13 20.2

d ± 0.5 17.1

e ± 0.31 3.7

ab ± 0.83 41.0

d ± 1.48

Values are means ± SD (n=4), Means with different superscripts (a, b, c, d) along the column

are significantly different (P ≤ 0.05), K – Kalukombu, MRB – Maharashtra Rabi Bajra, SRF –

semi refine flour, PC – pressure cooking, RDS – rapidly digestible starch, SDS – slowly

digestible starch, RS – resistant starch, TS – total starch,


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Starch is divided into 3 types considering the rate and extent of starch

digestion which includes rapidly digestible starch (RDS), slowly digestible starch

(SDS) and resistant starch (RS). Food processing is known to render some portion of

starch resistant to enzyme hydrolysis thereby influencing the starch fractions of food

(Englyst et al 1992). Changes in the starch fractions of pearl millet as a result of

processing are presented in Table 4.25. The raw and processed pearl millet flours

were gelatinized (flour to water ratio 1:4) prior to analysis and expressed on an as

eaten basis. K and MRB contained approximately 22% TS, 11% RDS, 7% SDS and

5% RS content. In general, the processing methods employed in this investigation

rendered the millet more digestible in comparison to the raw flour and also

correspondingly increased RS content. Milling, an important step in millet processing

has shown its influence on starch digestibility. The flour of pearl millet is coarse and

contains antinutrients like phytic acid, tannins and oxalates that form complexes with

nutrients leading to marked reductions in their digestibility (Arora et al 2003). Semi

refining of K variety drastically increased RS content. Although, bran which is a

physical barrier to enzymes and an important intrinsic factor limiting starch

hydrolysis was partially reduced or eliminated as a result of semi refining, it was high

in RS content. A combination of semi refining and gelatinization did not help in

improving starch digestibility. The high RS content could be explained by the fact that

the time taken for the process of gelatinization was perhaps too short to allow the

starch to completely gelatinize. Starch molecules present were entrapped inside the

granules which were not easily accessible to hydrolyzing enzymes (RS2) (Liljeberg,

2002). The seed coat/hull is an initial protective barrier for grains and plays an

important role in starch digestibility. The removal of hull renders the starch more


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accessible to hydrolytic enzymes leading to better digestibility. But in this study, the

slow rate of starch digestion in semi refined flour might be due to the presence of the

left out bran which led to the entrapment of starch in fibrous thick-walled cells

(Richard et al 2009, Asp 1994).

Millet subject to heat treatments (boiling, pressure cooking, roasting) reduced

the TS content. While, boiling or pressure cooking of pearl millet did not alter the RS

content a significant (P ≤ 0.05) drop in the millet subjected to roasting was noticed.

The process of cooking destroys the semi crystalline structure of raw starch granules

resulting in the loss of SDS and an increase of RDS. SDS content of food is important

as it gets hydrolyzed to glucose slowly yet completely in the small intestine, thereby

lowering the risk of chronic diseases such as cardiovascular diseases, obesity and

diabetes (Sureeporn et al 2010; Cousin et al 1996; Richard et al 2009). In this study

increase in the SDS and RDS content of heat treated millet in comparison to the raw

counterpart was seen. Increased starch digestibility after boiling/pressure cooking has

been reported in peas and beans (Richard et al 2009). The high RDS and SDS and low

RS content could be attributed due to heat treatments/gelatinization and dispersion of

the starch molecules rendering them more susceptible to attack by starch hydrolyzing

enzymes. A combination of high temperature and moisture caused greater disruption

of the cellular structure, increasing exposure of starch to amylolytic enzymes which

lead to a decrease in RS in boiled or pressure cooked millet.

Germination is a process which converts complex nutrients into simple ones

thereby improving its digestibility. Germination led to the significant increase in RDS

and SDS in both the varieties. A marked increase in the TS content as a result of

germination was seen. Degradation of starch in grains during germination led to the


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increase in dextrin and fermentable sugar. This change produces a special sweet

flavor in germinated brown rice (Kayahara, 2004). In germinated cereal grains,

hydrolytic enzymes are activated and decompose starch, non-starch polysaccharides,

and amino acids. The decomposition of high molecular weight polymers during

germination leads to the generation of bio-functional substances, and improvements in

organoleptic qualities due to the softening of texture and increase of flavor in cereal

grains (Kayahara 2004; Banchuen et al 2009).

Table – 4.26. Starch Digestion Index & Rapidly Available Glucose Values of

Processed Pearl Millet (g/100g)

Processing Starch Digestion Index Rapidly Available Glucose

K MRB K MRB

Whole flour (raw) 49 bc

± 2.1 50 b ± 2.3 13.7

a ± 0.2 13.2

a ± 0.7

Semi refined flour 43 a ± 2.0 41

a ± 0.5 17.5

b ± 0.6 17.3

c ± 0.5

Boiling 47 abc

± 1.0 51 b ± 0.2 20.5

c ± 0.3 22.4

e ± 0.3

Pressure cooking 46 ab

± 1.4 45 a ± 1.4 17.4

b ± 0.4 14.6

b ± 0.3

Roasting 51 c ± 0.5 51

b ± 1.1 18.6

b ± 0.2 20.9

d ± 0.6

Germination 52 c ± 0.4 49

b ± 0.8 22.8

d ± 0.5 26.3

f ± 0.4

Values are mean ± SD (n = 4), Means with different superscripts (a, b, c, d, f) along the column are

significantly different (P ≤ 0.05), K – Kalukombu, MRB – Maharashtra Rabi Bajra.


Page 150

Changes in the SDI and RAG content of processed pearl millet is presented in

Table 4.26. Overall, processing treatments significantly (P ≤ 0.05) affected the SDI

and RAG content of pearl millet. The changes in the SDI and RAG content of two

pearl millet varieties, however, were different. Semi refining decreased SDI

considerably. For example, raw flour of K and MRB varieties had SDI of 49 and 50

respectively; corresponding values were decrease to 43 and 41 after semi refining the

whole flour. Heat treatments and germination did not cause any significant changes in

the SDI of pearl millet.

Rapidly Available Glucose (RAG) content is a major determinant of the

magnitude of glycemic index. The % increase in RAG content for both the varieties

varied with processing techniques used. The raw flour of K and MRB had RAG value

of about 13%. The RAG content increased to about 27, 21, and 20% in germinated,

boiled and roasted millet respectively. Medium increase was seen in semi refined

flour and pressure cooked milled ranging from 14.6 to 17.5%.


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Table 4.27. Effect of Processing on % In–Vitro Protein Digestibility of Pearl

Millet

Processing % In-Vitro Protein Digestibility

Kalukombu MRB

Whole Flour 45.5 ab

± 1.1 49.3 a ± 7.9

Semi Refined Flour 54.8 abc

± 9.1 55. 3

a ± 7.9

Bran Rich Fraction 59.6 ac

± 4.0 69.9 bd

± 8.9

Boiling 32.5 a ± 4.3 58.2

ab ± 5.0

Pressure cooking 43.6 ab ± 4.1 45.5 a ± 3.1

Roasting 65.8 c ± 10.8 75.4 cd ± 1.4

Germination 88.2 d ± 6.6 78.9 d ± 7.8


MRB – Maharashtra rabi bajra.

Data in Table 4.27 indicated that protein digestibility of pearl millet was low

(45.5% for K and 49.3% for MRB variety). The relatively low protein digestibility

may be attributed to the influence of antinutrients such as enzyme inhibitors, lectins,

phytates, tannins and dietary fiber which inhibits protein digestion and also due to

presence of protein structures that resist digestion. Studies have demonstrated that

high-tannin sorghum varieties formed indigestible protein–tannin complexes which

are a major limiting factor in protein utilization (Chibber et al 1980). Semi refining of

the whole flour did not alter the protein digestibility, however, the BRF showed


Page 152

higher %IVPD than whole flour and was comparable to that of wheat bran (69%)

(Saunders et al 1972).

Results on the effect of heat treatments like boiling, pressure cooking and roasting

on IVPD significantly (P ≤ 0.05) varied between the two varieties. Wet heat

treatments such as boiling or pressure cooking did not alter the protein digestibility of

the millet which was in agreement with earlier reports on some cereals and legumes.

Protein cross-linking mainly through disulphide bonding and reduced protein

extractability in cooked samples appears to be the most important factor affecting

protein digestibility in cooked cereals (Aisha et al 2004; Vijayakumari et al 2007;

Singh et al 1981). In contrast, cooking improved %IVPD in foxtail, finger and

common millet (Ravindran 1992). Nevertheless, roasting markedly improved IVPD of

pearl millet from 45.5% to 65.8% in K variety and 49.3% to 75.4% in MRB

suggesting that dry heat treatment is more effective in improving protein digestibility.

The improvement as a result of dry heat treatment may be due to protein denaturation

and/or decreasing resistance of protein to enzyme attack (Sathe et al 1982).

Germination significantly (P≥0.05) improved the protein digestibility in both

varieties compared to the un-germinated millet (from 45.5% to 88.2% for K variety

and 49.3% to 78.9% for MRB variety). These findings are in agreement with an

earlier study on pearl millet (Anurag et al 1996). The increase in %IVPD can be

attributed to an increase in soluble proteins, due to partial hydrolysis of storage

proteins by endogenous proteases produced during the germination process. Such

partially hydrolyzed storage proteins may be more easily available for pepsin

digestion (Bhise et al 1988).


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Table 4.28. Association of % IVPD with Tannin and Dietary Fiber Content of

Pearl Millet

Dependent

variable

Independent

variable

Correlation

coefficient

% IVPD

Tannins 0.605**

IDF 0.034

SDF 0.168

TDF 0.046

** Correlation is significant at 0.01 level (2–tailed), IDF – Insoluble Dietary Fiber, SDF –

Soluble Dietary Fiber, TDF – Total Dietary Fiber

Tannins and dietary fiber are well known for their ability to bind and

precipitate protein. A correlation study was carried out between tannins, TDF, IDF

and SDF with %IVPD to ascertain whether protein digestibility of pearl millet was

influenced by these factors (Table 4.28). A positive correlation, was found between %

IVPD and tannin content (r = 0.605, P ≤ 0.01). For IDF, SDF and TDF the

correlations were positive although not significant. In this study, protein digestibility

of pearl millet showed a strong association with tannin levels. The low protein

digestibility of pearl millet was not due to tannins or dietary fiber content. It could be

due to other factors like interaction of proteins with non-protein components and the

proteins themselves thereby affecting their digestibility (Duodu et al 2003; Abdalla et

al 1997).

Results from the present study shows that relatively bioaccessible iron and

calcium content (in-vitro) was higher in MRB than K variety. Semi refining, heat


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treatments or germination of pearl millet improved the bioaccessible iron and calcium

in both varieties. Drastic improvement in bioaccessible iron content as a result of

various processing methods was seen in MRB, while increase in bioaccessible

calcium was similar in both varieties. Cooking effectively improved calcium

accessibility while the same was less effective in improving bioaccessible iron

suggesting that calcium and iron combined in a meal may decrease iron

bioaccessibility. Use of tap/de – mineralized water for boiling, pressure cooking or

germination led to an increase in the bioaccessible iron and calcium content,

nonetheless, this increase was not statistically significant. Changes in mineral and

antinutrient content during processing led to significant variations in the

antinutrient/mineral molar ratios which had a positive impact on the bioaccessible

iron and calcium content. Milling fractions like WF, SRF and BRF exhibited higher

RS values while a considerable decrease of the same due to heat treatment or

germination was seen due to complete starch digestion. Lower in-vitro protein

digestibility was seen in pearl millet. Milling, roasting and germination respectively

were more effective in improving the protein digestibility of pearl millet. A positive

correlation, was found between % IVPD and tannin content (r = 0.605, P ≤ 0.01). For

IDF, SDF and TDF the correlations were positive but not significant.


Page 155

CHAPTER – 5

UTILIZATION OF PEARL MILLET IN FOOD PRODUCTS

Pearl millet has a considerable potential to be used as foods and beverages. It

can be used as cooked, whole, dehulled or ground flour or else as a grain like rice.

The millet is mostly used as whole flour for traditional food preparation and hence

confined to traditional consumers and to people of lower economic strata. The flour

prepared out of pearl millet is coarse and has a grey to yellow color which imparts

bitter taste (Olatungi et al 1982).

Pearl millet is gluten-free and hence suitable for celiacs. Celiac disease is a

permanent gluten intolerance elicited in the genetically susceptible subject after

ingestion of gluten containing cereals (Laurin et al 2002). Celiac disease is a disorder

of considerable and increasing importance in Western countries occurring in 1 of 130

– 300 in the European population and in 1 of 111 of the US population (Green et al

2007; Joseph 1999). Celiac disease was recognized in northern India, primarily in

children, since the 1960s (Walia et al 1966).

Besides being rich in iron, calcium, zinc and high level of fat, it is nutritionally

comparable and even superior to major cereals due to the energy and protein value

(Fasasi 2009; Anu Sehgal et al 2006; Malik et al 2002). Owing to its superior

nutritional quality, the aim of the present investigation was to explore the possibility

of using pearl millet flour in food products. These products were analyzed for

proximate composition, nutritionally important starch fraction, and mineral

bioaccessibility. Sensory and shelf life studies were also carried out. Products like

ladoo and burfi were stored in steel containers for 4 – 5 weeks while cookies were

stored in PET – PP and foil for 12 weeks. These products were analyzed for moisture


Page 156

content, free fatty acids and peroxide value. Acceptability studies as affected by

storage were also carried out.

Table – 4.29. Proximate Composition of Breakfast Items Prepared from Pearl

Millet (dry weight basis).

Breakfast

Items

Moisture

(g)

Protein

(g)

Fat

(g)

Ash

(g)

Iron

(mg)

Calcium

(mg)

Phosphorus

(mg)

Dosa

Rice (C) 56.9 b ± 1.7 7.8

b ± 0.2 5.0

a ± 0.1 1.67

a ± 0.1 0.7

2

a ± 0.0 18.4

a ± 0.1 152.6

a ± 2.6

K 51.6 a ± 0.7 5.3

a ± 0.3 6.9

b ± 0.7 2.90

b ± 0.1 3.24

b ± 0.2 56.4

b ± 5.1 271.1

c ± 28.0

MRB 51.6 a ± 0.9 6.0 a ± 0.4 6.0 ab ± 0.3 3.39 b ± 0.6 3.37 b ± 0.3 58.9 b ± 3.1 267.3 b ± 13.2

Roti

Rice (C) 65.0 b ± 1.0 7.4

b ± 0.3 5.4

b ± 0.4 2.

10

a ± 0.1 0.7

a ± 0.0 25.2

a ± 1.1 131.6

a ± 2.6

Ragi (C) 33.0 a ± 0.2 7.7

b ± 0.1 5.5

b ± 0.4 3.10

b ± 0.1 3.5

b ± 0.4 325.7

c ± 7.7 243.2

b ± 2.7

K 63.6 b ± 0.8 6.6

a ± 0.2 4.2

a ± 0.2 2.42

c ± 0.1 4.5

c ± 0.4 57.6

b ± 6.2 331.4

c ± 9.7

MRB 69.9 c ± 0.4 7.5

b ± 0.3 5.2

b ± 0.2 2.47

c ± 0.1 4.2

c ± 0.3 50.1

b ± 2.1 296.8

c ± 17.4

Puttu

Rice (C) 61.5 b ± 0.1 8.2

b ± 0.2 8.5

b ± 0.4 2.1

b ± 0.2 0.7

a ± 0.02 22.0

a ± 0.6 125.2

a ± 4.1

Ragi (C) 28.6 a ± 0.3 7.5

ab ± 0.4 6.6

a ± 0.4 1.8

a ± 0.0 3.5

b ± 0.4 377.6

c ± 11.8209.6

b ± 26.2

K 56.6 b ± 2.6 6.5

a ± 0.4 10.2

c ± 0.1 2.7

c ± 0.0 4.5

c ± 0.4 45.2

b ± 0.4 287.4

c ± 15.3

MRB 58.1 b ± 2.9 6.5

a ± 0.4 10.4

c ± 0.4 1.7

a ± 0.0 4.2

c ± 0.3 40.3

b ± 0.4 247.6

b ± 14.0


C – Control, K – Kalukombu, MRB – Maharashtra Rabi bajra.


Page 157

In order to evaluate the influence of pearl millet in product preparation,

selected breakfast items typical of Indian cuisine such as dosa, roti and puttu were

prepared and its nutritional profile was studied by comparing with traditionally

prepared breakfast meals containing rice/ragi as major ingredients. The data indicated

that incorporation of pearl millet in dosa significantly (P ≤ 0.05) lowered moisture

and protein content, while, increased the fat content (Table 4.29). For instance,

traditionally prepared rice dosa contained 56.9% and 7.8% of moisture and protein,

the corresponding values decreased to about 51% and 5.7% respectively upon

substitution with pearl millet, while the fat content increased from 5.0% to 6.5%.

Addition of pearl millet in dosa greatly increased ash content and therefore rich in

iron, calcium and phosphorus.

Traditionally prepared rotis based of rice and ragi was used for comparison.

The protein and fat content of MRB Roti was similar to that of rice and ragi roti

(ranging from 7.4 – 7.7% and 5.2 – 5.5% respectively), although, a lower protein

(6.6%) and fat (4.2%) content was seen in roti prepared using K variety. High ash and

mineral content was seen in pearl millet rotis. However highest increase in calcium

was seen in ragi roti. This is because ragi is a rich source of calcium than pearl millet

and rice.

Puttu prepared out of 100% pearl millet was compared with traditionally

prepared rice and ragi puttu. The protein content of pearl millet puttu was

significantly (P ≤ 0.05) lower than those of rice and ragi puttu. Significant (P ≤ 0.05)

increase in the fat, ash and mineral content was seen in pearl millet puttu; however

ragi puttu had the highest levels of calcium.


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In general, the results indicated that breakfast items prepared by either partial

or 100% substitution increased fat, ash and minerals like iron, calcium and

phosphorus. The nutrient profile of breakfast items prepared out of K and MRB was

similar.

Table – 4.30. In-Vitro Bioaccessible Iron and Calcium Content of Breakfast

Items Prepared from Pearl Millet (per 100g)

Breakfast

products

Bioaccessible Iron Bioaccessible Calcium

Mg/100g % Mg/100g %

Dosa

Rice (C) 0.125 a ± 0.01 17 5.00

a ± 0.4 27

Kalukombu 0.330 c ± 0.12 10 33.50 c ± 2.1 59

MRB 0.210 b ± 0.03 6 32.30

b ± 2.5 55

Roti

Rice (C) 0.135 a ± 0.00 19 5.6

a ± 0.7 23

Ragi (C) 0.533 c ± 0.06 15 71.2

c ± 8.5 22

Kalukombu 0.311 b ± 0.00 7 35.8

b ± 3.1 62

MRB 0.350 b ± 0.09 8 29.4 b ± 2.7 59

Puttu

Rice (C) 0.425 b ± 0.01 28 8.99

a ± 0.5 41

Ragi (C) 0.280 a ± 0.01 13 83.03 c ± 4.7 22

Kalukombu 0.680 bc

± 0.19 13 20.3 b ± 1.8 45

MRB 0.540 bc ± 0.17 12 20.20 b ± 1.1 50


(P ≤ 0.05), C – Control, MRB – Maharashtra Rabi bajra.


Page 159

The bioaccessible iron content of dosa, roti and puttu prepared from rice flour was

0.125, 0.135 and 0.425 mg/100g, respectively (Table 4.30). Whole or partial

incorporation of pearl millet flour into these products brought about a significant (P ≤

0.05) increase in the bioaccessible iron content, for example, the corresponding values

increased to about 0.27, 0.33 and 0.61mg/100g respectively. However, these values

were lower compared to ragi based roti and puttu. Ragi is a rich source of iron and

calcium and hence it showed a positive influence on bioaccessible iron and calcium.

Although bioaccessible iron content of pearl millet based products increased, its %

bioaccessibility remained lower than rice products. The highest % bioaccessible iron

content was registered for rice than pearl millet or ragi based products.

The addition of pearl millet enhanced bioaccessible calcium content (mg/100 g) as

well as % bioaccessibility in all the products. The % bioaccessibility of calcium was

even higher than ragi based products. The highest increase in bioaccessible calcium

was seen in roti followed by puttu prepared using pearl millet.


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Table – 4. 31: Nutritionally Important Starch Fractions (In-vitro) of Breakfast Items from Pearl Millet (g/100g)

Breakfast

Products Dry matter TS RDS SDS RS SDI RAG

Dosa

Rice (C) 43.2 a ± 2.03 48. 6 b ± 0.03 25.8 c ± 0.08 19.6 c ± 0.11 3.1 a ± 0.21 53 b ± 0.17 34.7 c ± 0.09

Kalukombu 47.5 a ± 0.01 48.1

b ± 0.94 20.4

b ± 0.63 13.2

b ± 0.73 15.6

b ± 0.35 42

a ± 2.11 30.2

b ± 0.27

MRB 48.4 a ± 1.13 37.9

a ± 0.58 15.4

a ± 0.52 10.7

a ± 0.39 12.3

b ± 0.21 41

a ± 1.17 24.5

a ± 0.22

Roti

Rice (C) 34.9 b

± 1.29 37.8 a ± 2.06 21.5

a ± 1.05 11.8

a ± 1.01 4.5

b ± 0.28 57

a ± 0.46 24.4

a ± 1.11

Ragi (C) 66.9 c ± 0.21 41.4 b ± 0.73 26.5 b ± 1.00 14.6 b ± 0.26 0.24 a ± 0.24 64 c ± 1.29 29.5 b ± 0.20

Kalukombu 36.4 b ± 0.94 34.5 a ± 0.23 20.7 a ± 0.25 10.2 a ± 0.44 3.6 b ± 0.20 60 b ± 0.41 24.5 a ± 0.20

MRB 30.3 a ± 0.62 35.0

a ± 0.33 20.7

a ± 0.39 9.9

a ± 0.51 4.3

b ± 0.37 59

ab ± 0.79 25.3

a ± 0.40

Puttu

Rice (C) 38.5 a ± 0.14 45.0

a ± 1.82 24.0

a ± 0.43 13.6

a ± 0.85 7.2

b ± 0.44 54

a ± 1.31 28.6

a ± 0.63

Ragi (C) 73.9 b ± 2.86 47.2 a ± 0.87 27.4 b ± 0.21 19.2 c ± 0.58 0.92 a ± 0.11 58 a ± 0.64 30.5 b ± 0.23

Kalukombu 43.4 a ± 3.21 56.3 c ± 2.18 31.3 d ± 0.59 16.9 b ± 0.87 8.1 b ± 0.20 56 a ± 2.69 37.7 c ± 2.65

MRB 41.9 a ± 3.50 52.1 b ± 0.59 29.2 c ± 1.08 13.7 a ± 0.29 9.2 b ± 0.76 56 a ± 0.62 36.9 c ± 0.09

Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05), MRB – Maharashtra Rabi bajra, C –

Control, TS – Total starch, RDS – Rapidly digestible starch, SDS – Slowly digestible starch, RS – Resistant starch, SDI – Starch

digestion index, RAG – Rapidly available glucose.


Page 161

Nutritionally important starch fractions of breakfast products prepared from

two pearl millet varieties (K and MRB) and rice/ragi (control) were analyzed in vitro

and exhibited in Table 4.31. Pearl millet was used in the preparation of roti, dosa and

puttu. Dosa is a fermented breakfast item while puttu is a streamed product. Total

starch content of dosa prepared out of rice and K variety (48%) were similar while

MRB had low starch content (37.9%). Starch in rice dosa was rapidly available

(25.8%) with low levels of SDS (19.6%) and RS (3.1%). Higher starch digestibility

was found in rice dosa (control) as it was prepared with higher amounts of rice along

with some minor ingredients. Replacement of rice with pearl millet reduced RDS and

SDS to about 17.9% and 12% respectively, while, greatly increased RS to 14%.

Significant reduction in RAG and SDI was also noticed.

The rotis were prepared by adding warm water and a pinch of salt to the

respective flour and mixed into dough, then flattened into round shaped roti and

shallow fried (150 – 200oC) on a pan. Cereal and millet based rotis were used as

controls. TS content of ragi roti (41.4%) was higher than rice (37.8%) and pearl millet

roti (35%). Ragi roti had significantly (P ≤ 0.05) higher RDS (26.5%) and SDS

(14.6%) content, where as rice and pearl millet rotis were low in RDS and SDS which

of about 21% and 10.7% respectively. Ragi roti was found to contain minor amounts

of RS (0.24%), whereas, higher RS was found in rice and pearl millet roti ranging

from 3.6 to 4.5%. SDI and RAG values were higher for ragi roti and lower for rice

and pearl millet roti respectively.

Puttu is a steamed product served with desiccated coconut and sugar. Cereal

(rice) and millet (ragi) based controls were used for comparison. Unlike dosa and roti,

rice and ragi puttu were found to have low TS and RDS content. Compared to ragi


Page 162

dosa or roti, puttu prepared out of ragi had considerable amount of RS (0.92%), yet, it

was lower than rice and pearl millet based puttu. SDI was similar for all the products

while RAG values ranged from 28.6% for rice to about 37% for pearl millet based

products.

Table – 4.32. Sensory Analysis of Breakfast Items Prepared from Pearl Millet

Breakfast

products Color Flavor Texture Taste

Overall

Acceptability

Dosa

Rice (C) 7.7 c ± 0.69 7.6

b ± 0.55 7.8

b ± 0.60 7.9

b ± 0.79 7.7

b ± 0.63

K 6.8 b ± 0.76 6.7 a ± 1.06 7.0 a ± 0.89 6.7 a ± 1.00 6.8 a ± 0.83

MRB 6.2 a ± 1.15 6.7

a ± 1.18 6.6

a ± 1.52 6.6

a ± 1.60 6.8

a ± 1.28

Puttu

Rice (C) 7.6 b

± 0.96 7.0 ab

± 0.88 7.3 a ± 0.97 7.1

b ± 1.16 7.

3

b ± 0.92

Ragi (C) 6.7 a ± 0.99 7.5

b ± 0.84 7.2

a ± 1.03 7.2

b ± 0.75 7.3

b ± 0.63

K 6.8 a ± 1.21 6.9

ab ± 1.03 6.9

a ± 1.08 7.0

b ± 1.02 7.1

ab ± 0.84

MRB 6.7 a ± 1.15 6.8

a ± 1.03 6.8

a ± 1.09 6.4

a ± 1.19 6.6

a ± 1.06

Roti

Rice (C) 7.8 b ±0.90 7.4

b ±0.76 7.4

b ±1.04 7.7

ab ± 0.91 7.7

b ± 0.83

Ragi (C) 6.8 a ±1.12 7.5 b ±0.90 7.6 b ±0.72 7.7 b ± 0.78 7.5 ab ± 0.77

K 6.4 a ±0.97 7.2

ab ± 0.86 7.3

ab ± 0.92 7.7

ab ± 1.03 7.4

ab ± 0.89

MRB 6.4 a ± 0.93 6.7 a ± 1.01 6.8 a ± 0.96 7.1 a ± 1.01 7.0 a ± 0.93

Means followed by different letters (a, b, c) in the same column differ significantly (P < 0.05),



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The sensory evaluation of breakfast products is presented in Table 4.32. The

sensory evaluation results for dosa prepared from rice and pearl millet respectively,

revealed that the scores for parameters like color, flavor, texture and overall

acceptability obtained for rice dosa were higher than that of pearl millet dosa. Based

on the hedonic ratings, pearl millet dosa was less preferred by the panelists than rice

dosa. The color score of pearl millet puttu was lower than rice puttu, while, no

significant difference was found with the color scores of ragi puttu. Replacement with

pearl millet did not affect the flavor, taste, texture and overall acceptability of puttu.

Roti prepared from MRB had the lowest scores for all the parameters while; roti from

K variety had scores similar to those prepared from rice or ragi. In a hedonic scale of

9 points, a score of 6 is considered a quality limit (Munoz et al 1992).The three

different products prepared from rice, ragi and pearl millet respectively exhibited

scores appreciably higher than the quality limit (6.2 to 7.9). Overall, pearl millet

incorporation substantially affected the color of the products; however the scores were

in the acceptable range.


Page 164

Table 4.33. Proximate Composition of Wheat flour (Control) and Pearl Millet

Cakes

Cake Moisture

(g)

Fat

(g)

Proteins

(g)

Ash

(g)

Iron

(mg)

Calcium

(mg)

Phosphorus

(mg)

Control 13.9 b ± 0.3 25.7

a ± 0.6 5.9

a ± 0.4 0.62

a ± 0.1 2.2

a ± 0.1 13.9

b ± 0.2 112.6

a ± 0.8

K 12.30a ± 0.2 25.6

a ± 0.4 6.3

b ± 0.2 0.84

c ± 0.0 4.4

c ± 0.0 13.2

a ± 0.2 124.8

b ± 0.6

MRB 13.3 b ± 0.1 26.7

b ± 0.6 8.5

c ± 0.5 0.69

b ± 0.0 2.8

b ± 0.0 15.8

c ± 0.7 134.0

c ± 2.0

Means followed by different letters (a, b, c) in the same column differ significantly (P ≤ 0.05), K –

Kalukombu, MRB – Maharashtra Rabi bajra.

Cakes were baked by replacing refined wheat flour with 40% pearl millet and

compared with cake prepared with 100% refined wheat flour. Data in Table 4.33

presents proximate composition of cake incorporated with 40% pearl millet (K and

MRB). The fat content of the cake increased when fortified with 40% MRB. Since

pearl millet is richer in protein content than refined wheat flour, incorporation of

cakes with pearl millet enhanced protein content (increased from 5.9 (control) to 6.3

and 8.5 for K and MRB). The mineral content of cakes baked with 40% pearl millet

was also higher.


Page 165

Table 4.34. Proximate Composition of Wheat flour (Control) and Pearl Millet

Buns

Bun Moisture

(g)

Fat

(g)

Proteins

(g)

Ash

(g)

Iron

(mg)

Calcium

(mg)

Phosphorus

(mg)

C 26.2 c ± 0.6 11.4

b ± 0.3 12.3

c ± 0.5 1.1

a ± 0.10 1.3

a ± 0.0 40.1

a ± 0.0 108.9

a ± 0.8

K 27.8 b ± 1.2 10.8

a ± 0.6 11.4

b ± 0.4 1.6

b ± 0.10 1.5

b ± 0.0 56.0

b ± 0.8 143.5

b ± 0.4

MRB 22.4 a ± 0.2 13.2 c ± 0.9 9.7 a ± 0.3 1.6 b ± 0.00 1.8 c ± 0.0 60.5 c ± 0.4 155.7 c ± 0.5



Buns were prepared by incorporating 40% pearl millet (K and MRB) and

compared with bun prepared using 100% refined wheat flour (Table 4.34). Buns

fortified with Pearl millet contained fat and protein higher than control. Incorporation

of pearl millet had higher levels of ash content thereby contributing to higher levels of

mineral content. Minerals such as iron, calcium and phosphorus were considerably

high in buns baked using 40% pearl millet than 100% refined wheat flour.


Page 166

Table – 4. 35a. Sensory Analysis of Wheat flour (Control) and Pearl Millet Cakes

Cake Color Flavor Texture Taste Overall

Acceptability

Control 7.7 b ± 0.96 7.6 b ± 0.74 7.5 a ± 0.80 7.8 b ± 0.79 7.8 b ± 0.72

K (40%) 6.9 a ± 0.96 7.6

b ± 0.97 7.2

a ± 0.99 7.6

ab ± 1.05 7.6

b ± 0.82

MRB (40%) 6.7 a ± 0.95 6.8

a ± 1.02 7.2

a ± 0.87 7.1

a ± 1.02 7.1

a ± 0.84


Control – 100% wheat flour, K – Kalukombu (60:40 wheat flour: pearl millet flour), MRB –

Maharashtra Rabi bajra (60:40 Wheat flour: Pearl millet flour)

Table – 4. 35b: Sensory Analysis of Wheat flour (Control) and Pearl Millet Buns

Bun Control K MRB

Wt. of Bun (g) 63.784 b ±0.80 48.589

a ±0.99 48.573

a ±0.95

Vol. of Bun (mL) 190 b ±2.1 140

a ±2.5 140

a ±2.9

Crust shape Normal Normal Normal

Crumb grain Medium fine Medium fine Slightly soft

Texture Soft Very soft Slightly soft

Eating quality Typical Appealing

wholesome taste Typical

Means followed by different letters (a, b) in the same column differ significantly (P ≤ 0.05), K

– Kalukombu, MRB – Maharashtra Rabi bajra.


Page 167

As shown in Table 4.35a, the color score was higher for control cake (7.7)

than 40% pearl millet cake (6.9 for K and 6.7 for MRB). However, these sensory

scores were within the acceptable range. Flavor scores were similar for control and

40% K variety cakes (7.6 each) than those prepared with 40% MRB flour (6.8).

Texture, taste and overall acceptability scores for control, 40% K and 40% MRB flour

fortified cakes were similar and were markedly higher than 6, which are considered as

the quality limit of a product. All the sensory scores given by the panelists revealed

that the cakes prepared by fortifying with 40% K or MRB flour were acceptable.

The data presented in Table 4.35b showed that incorporation of pearl millet

flour (40%) decreased the weight and volume of buns significantly (P ≤ 0.05) from 63g

to about 48g in weight and from 190ml to 140 ml in volume. The crust shape of

control and pearl millet buns was normal, while crumb grain which was medium fine

in case of control and K bun, was slightly soft in case of MRB bun. On the whole, the

addition of pearl millet particularly K variety flour improved the eating quality of the

bun and resulted in a wholesome appealing taste.


Page 168

Table 4.36. Effect of Storage of Bun at Room Temperature on Mould Growth.

Bun Mould growth appearance

Control First evidence of mould growth on 4th day of storage

Kalukombu First appearance of mould growth on 5th

day of storage

MRB First appearance of mould growth on 3rd

day of storage

MRB – Maharashtra Rabi bajra

Table 4.37: Effect of Storage of Cake at Room Temperature on Mould Growth

Cake Mould growth appearance

Control First appearance of mould growth on 13th day of storage

Kalukombu First appearance of mould growth on 12th

day of storage

MRB First appearance of mould growth on 11nt

day of storage

MRB – Maharashtra Rabi bajra

Buns and cakes baked using pearl millet flour was packed in airtight polythene

covers and were placed in an area sterilized with alcohol. They were observed for

mould growth and compared with the standard (conventionally prepared). Appearance

of mould growth in conventionally prepared bun and cake was observed on 4th and

13th day of storage respectively (Table 4.36 & 4.37). While those prepared by addition

of MRB (40%) had mould growth on 3rd

and 11th

day of storage and K variety (40%)

showed mould growth on the 5th and 12th

day respectively. The appearance of mould


Page 169

growth in standard and pearl millet flour (40%) buns and cakes was almost same and

was storable up to about 3 – 4 days for buns and 11 – 12 days for cake.

Table – 4. 38: Proximate Composition of Traditional Sweets Prepared from

Pearl Millet.

Sweets Moisture

(g)

Fat

(g)

Proteins

(g)

Ash

(g)

Iron

(mg)

Calcium

(mg)

Phosphorus

(mg)

Ladoo

C 0.11a ± 0.0 17.17 b ± 0.3 9.20 c ± 0.2 1.84b ± 0.0 2.49a ± 0.0 21.70b ± 0.0 203.2 c ± 5.5

K 0.22c ± 0.0 16.18

a ± 0.0 7.75

a ± 0.5 0.91

a ± 0.0 4.98

b ± 0.1 19.21

a ± 0.7 175.7

b ± 1.3

MRB 0.18b

± 0.0 19.06 c ± 1.0 8.73

b ± 0.1 1.95

b ± 0.0 6.43

c ± 0.1 27.56

c ± 0.7 163.6

a ± 1.1

Burfi

C 0.12b

± 0.0 25.8 c ± 0.3 9.37

b ± 0.3 1.6

b ± 0.0 2.64

a ± 0.0 30.90

c ± 0.7 191.2

a ± 2.1

K 0.13c ± 0.0 19.9

b ± 0.3 7.80

a ± 0.2 1.0

a ± 0.0 5.51

b ± 0.0 20.88

b ± 0.7 217.1

b ± 0.6

MRB 0.11a ± 0.0 16.0 a ± 0.7 9.20 b ± 0.5 0.9 a ± 0.0 6.03 c ± 0.1 13.36 a ± 0.0 194.4 a ± 3.1


C – control, K – Kalukombu, MRB – Maharashtra rabi bajra.


Page 170

Indian traditional sweets such as ladoo and burfi were prepared using pearl

millet flours (K and MRB) and compared with traditionally prepared sweets for its

nutrient composition (Table 4.38). The moisture content of ladoo and burfi prepared

from K was higher than the control. Traditionally prepared sweets had higher protein

content while those prepared using pearl millet were comparatively low in protein.

However, significantly higher iron content was found in pearl millet sweets than those

prepared using gram flour. The higher values of iron in pearl millet sweets can be

attributed to the higher iron content in the millet.

Table – 4. 39: Sensory Analysis of Traditional Sweets Prepared from Pearl

Millet.

Traditional

sweets Color Flavor Texture Taste

Overall

Acceptability

Ladoo

Control 7.2 b ± 0.98 6.5 a ± 0.84 6.6 a ± 0.83 6.3 a ± 0.81 6.2 a ± 0.90

Kalukombu 6.5 ab

± 1.23 7.4 b

± 0.71 7.0 a ± 0.90 7.6

b ± 0.57 7.4

b ± 0.71

MRB 6.0 a ± 1.07 6.5

a ± 1.08 6.6

a ± 1.02 6.7

a ± 1.21 6.6

a ± 1.07

Burfi

Control 7.1 b

± 0.87 6.4 a ± 1.01 6.4

a ± 0.90 6.8

ab ± 1.03 6.8

a ± 1.01

Kalukombu 6. 4

a ± 0.76 7.1

a ± 0.83 6.5

a ± 0.90 7.4

b ±x 0.76 7.1

a ± 0.70

MRB 6.2 a ± 0.53 6.4

a ± 0.96 6.1

a ± 0.91 6.6

a ± 0.95 6.4

a ± 0.76

Means followed by different letters (a, b, c) in the same column differ significantly (P < 0.05),

MRB – Maharashtra rabi bajra.


Page 171

Ladoo and burfi are the two traditional sweets prepared using gram flour as a

base ingredient. In this study these traditional sweets were prepared with pearl millet

and compared with the traditionally prepared. The control burfi and ladoo had a high

color score of 7.2 and 7.1 respectively (Table 4.39). While those prepared out of pearl

millet had low scores ranging between 6 – 6.5. The flavor, taste, texture and overall

acceptability scores for ladoo and burfi made from K variety were higher than control

and MRB. The scores for all the sensory parameters of ladoo and burfi made from

gram flour and pearl millet were higher than 6, suggesting that these products were

acceptable.


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Table – 4.40: Effect of Storage on Sensory Attributes of Pearl Millet Ladoo

LADOO Color Flavor Texture Taste Overall

Acceptability

Control

Week – 0 7.2 ab ± 0.98 6.5 a ± 0.84 6.6 ab ± 0.83 6.3 ab ± 0.81 6.2 a ± 0.90

Week – 1 7.9 b

± 0.88 7.1 a ± 1.14 6.7

ab ± 1.01 7.2

c ± 1.25 7.2

b ± 1.12

Week – 2 7.6 ab

± 0.87 7.2 a ± 0.72 7.0

b ± 0.64 7.4

c ± 0.83 7.2

b ± 0.72

Week – 3 7.4 ab ± 0.84 7.0 a ± 0.77 6.8 ab ± 0.54 7.0 bc ± 0.89 6.9 ab ± 0.63

Week – 4 6.9 a ± 1.58 6.4

a ± 1.77 6.1

a ± 1.83 6.1

a ± 1.98 6.3

a ± 1.68

Kalukombu

Week – 0 6.5 a ± 1.23 7.4

a ± 0.71 7.0

a ± 0.90 7.6

a ± 0.57 7.4

a ± 0.71

Week – 1 6.7 a ± 0.88 7.5 a ± 0.81 7.1 a ± 0.86 7.6 a ± 1.13 7.5 a ± 1.00

Week – 2 6.1 a ± 1.61 7.4

a ± 0.67 7.4

a ± 0.73 7.6

a ± 0.74 7.6

a ± 0.68

Week – 3 7.0 a ± 1.10 7.4 a ± 0.94 7.2 a ± 1.03 7.4 a ± 1.13 7.4 a ± 1.02

Week – 4 6.8 a ± 1.72 7.4

a ± 1.52 7.4

a ± 1.69 7.5

a ± 1.52 7.8

a ± 0.73

MRB

Week – 0 6.0 ab

± 1.07 6.5 a ± 1.08 6.6

a ± 1.02 6.7

a ± 1.21 6.6

a ± 1.07

Week – 1 6.7 b

± 0.66 6.6 a ± 1.35 7.1

a ± 0.78 7.2

a ± 1.02 6.9

a ± 0.98

Week – 2 5.5 a ± 1.52 6.4 a ± 1.06 6.9 a ± 0.93 6.5 a ± 1.29 6.6 a ± 0.73

Week – 3 6.0 ab

± 1.36 6.8 a ± 0.97 6.7

a ± 1.11 6.6

a ± 1.16 6.6

a ± 1.06

Week – 4 6.4 b ± 1.62 6.9 a ± 1.55 6.7 a ± 1.46 6.6 a ± 1.49 6.7 a ± 0.91


MRB – Maharashtra Rabi bajra.


Page 173

Initially, the overall acceptability scores for of control, K and MRB ladoo was

6.2, 7.4 and 6.6 respectively (Table 4.40). K ladoo was preferred over control or MRB

ladoo. Color is an important sensory attribute of a food product. The color scores for

control ladoo (7.2) were higher than K (6.5) and MRB (6.0) on day 0. This indicated

that the yellowish color of the control ladoo was preferred by the panelists as

compared with the grayish color of the pearl millet ladoo. However, the color scores

for K and MRB ladoo increased to 6.8 and 6.4 respectively over the storage period,

indicating that the panelist liked the color of pearl millet ladoo after they got adapted

to it over the storage period of 4 weeks. The scores for all the sensory parameters of

control ladoo decreased from 2nd

week onwards, while the scores of pearl millet ladoo

(K and MRB) remained constant until the end of the study period. In particular,

sensory scores for flavor, texture, taste and overall acceptability showed no significant

differences throughout the study period.


Page 174

Table – 4.41: Effect of Storage on Sensory Attributes of Pearl Millet Burfi

BURFI Color Flavor Texture Taste Overall

Acceptability

Control

Week – 0 7.1 a ± 0.87 6.4 a ± 1.01 6.4 a ± 0.90 6.8 b ± 1.03 6.8 ab ± 1.01

Week – 1 7.4 a ± 0.85 6.7

a ± 0.99 6.8

a ± 0.80 7.0

b ± 0.98 7.0

b ± 0.81

Week – 2 7.7 a ± 0.96 6.7

a ± 0.92 6.5

a ± 0.91 7.0

b ± 1.09 6.8

ab ± 0.91

Week – 3 7.1 a ± 1.26 6.4 a ± 1.12 6.6 a ± 1.26 6.4 ab ± 0.98 6.4 ab ± 0.90

Week – 4 7.2 a ± 1.58 6.0

a ± 1.58 6.3

a ± 1.55 5.6

a ± 1.67 5.9

a ± 1.71

Kalukombu

Week – 0 6.4 ab

± 0.76 7.2 bc

± 0.83 6.5 a ± 0.90 7.4

b ± 0.76 7.1

abc ± 0.70

Week – 1 6.4 ab ± 0.67 6.5 a ± 0.86 6.7 a ± 0.91 6.7 a ± 0.88 6.6 a ± 0.89

Week – 2 5.9 a ± 1.75 7.3

c ± 0.66 6.6

a ± 1.18 7.5

b ± 0.78 7.3

b ± 0.74

Week – 3 6.5 ab ± 1.15 6.8 ab ± 1.09 6.4 a ± 1.21 6.7 a ± 1.31 6.6 abc ± 1.17

Week – 4 6.6 b ± 1.64 7.3

c ± 1.36 6.9

a ± 1.51 7.4

b ± 1.40 7.2

c ± 1.40

MRB

Week – 0 6.2 a ± 0.53 6.4

a ± 0.96 6.1

a ± 0.91 6.6

ab ± 0.95 6.4

ab ± 0.76

Week – 1 6.7 a ± 0.92 6.9

a ± 0.83 7.0

b ± 0.93 7.1

b ± 1.04 7.1

b ± 0.91

Week – 2 5.7 a ± 1.60 6.2 a ± 1.20 6.2 ab ± 1.00 6.5 ab ± 0.98 6.4 ab ± 0.94

Week – 3 5.6 a ± 1.47 6.5

a ± 1.09 6.3

ab ± 1.22 5.9

a ± 1.49 6.3

ab ± 1.20

Week – 4 5.9 a ± 1.63 6.1 a ± 1.60 6.4 ab ± 1.52 6.1 ab ± 1.73 6.0 a ± 1.52


MRB – Maharashtra rabi bajra


Page 175

Sensory evaluation of burfi as affected by storage is presented in Table 4.41.

Similar to ladoo, the color score of control burfi (7.1) was higher than K (6.4) and

MRB (6.2). However, the scores for color increased for burfi prepared from K over

the storage period of 4 weeks. The color scores of control burfi remained highest

throughout the storage period, while, values for taste and overall acceptability

decreased after 3 weeks of storage. Significantly, burfi made from pearl millet

retained acceptability throughout the storage period of 4 weeks. Therefore it may be

concluded that prolonged storage of pearl millet burfi may have induced desirable

changes in taste, texture and flavor. Burfi from K was more favored than MRB. It was

also noticed that scores for color, flavor, taste and overall acceptability of burfi from

K was highest at the end of 4th

week compared to MRB.


Page 176

Bars with different letters (a, b, c) differ significantly (P ≤ 0.05), C – Control, K – Kalukombu, MRB –

Maharashtra Rabi bajra.

Figure 4.9: Moisture, Peroxide value and Free Fatty Acid Content of Ladoo and

Burfi Prepared from Two Pearl Millet Varieties as Affected by Storage


Page 177

Moisture content is an important determinant of the shelf life of a product.

Migration of moisture produces changes in the texture, water activity and flavor of the

product. The moisture content of the ladoo and burfi prepared from pearl millet was

about 0.24% initially which increased to about 0.48% at the end of the storage period

(Fig. 4.9). The moisture content of pearl millet-burfi was higher while that of ladoo

was lower than their traditional counterparts. This increase did not affect the texture

of pearl millet sweets at the end of the 5th

week of storage; however those prepared

traditionally, were soggy at the end of 5th

week.

The peroxide value (PV) of an oil or fat is used as an indicator of rancidity

reactions that have occurred during storage. Peroxide value is the most widely used

method for determining autoxidation (oxidative rancidity), by measuring the amount

of iodine formed by the reaction of peroxides (formed in oil or fat) with iodide ion.

The peroxide value is the number that express, in milliequivalents of active oxygen,

the quantity of peroxide contained in 100g of fat. When fatty acids react with oxygen

they become peroxy radical. Hydroperoxides are unstable intermediates formed

during oxidation process. They further disintegrated to form a wide range of products

that are also unstable, in turn undergo oxidation to form stable products most of which

are responsible for disagreeable flavors associated with rancid oils (Eskin et al 2001).

There was a significant difference in the peroxide values between control and

pearl millet burfi/lodoo (Fig. 4.9). The peroxide value for traditional and pearl millet

burfi and ladoo was 0.00% which increased to about 1.41%. The differences between

the PV of traditional and pearl millet products although significant, were not large.

Free fatty acid (FFA) is a measure of hydrolytic rancidity in fats. A large

majority of fats are triglycerides which is a combination of glycerol with 3 fatty acids


Page 178

attached. Hydrolysis of triglycerides, in presence of water causes cleavage of ester

bonds that attach fatty acids residue to glycerol thus setting it free from glycerol. The

detached fatty acids from triglycerides are called free fatty acids. Essentially how

soon the triglycerides deteriorate, determines the shelf life of a product. A fatty acid

radical has an unpaired electron. Therefore they are short lived and are highly reactive

as they seek a partner for their unpaired electron.

Pearl millet triglycerides contains about 74% unsaturated fatty acids

(oleic, linolic and linolenic acids) and the remaining fraction is made up of saturated

fatty acid residues (palmitic and steric acids). Pearl millet germ is proportionally

larger than other cereal grains and has major fraction (88%) of lipids stored in the

germ. The relatively high proportions of polyunsaturated fatty acids that constitute the

triglycerides negatively affect the shelf life of pearl millet flour (Lai et al 1980;

Taylor 2004). Hydrolysis of triglycerides and subsequent oxidation of the released

de – esterified unsaturated fatty acids occur during the ambient storing conditions.

This hydrolysis is catalyzed by lipase enzyme. It is these chemical changes that are

manifested as undesirable tasted and odors in millet flours that has been stored

(Taylor 2004).

In this study, the free fatty acid value is expressed as palmitic acid

equivalents/100g of ladoo/burfi. FFA content increased progressively during storage

of ladoo and burfi (Fig. 4.9). The free fatty acid levels increased more rapidly in the

sweets prepared from pearl millet compared to those traditionally prepared. The free

fatty acid for stored control, K and MRB ladoo increased from 0.63, 0.69 and 0.74 to

0.89, 1.15 and 1.13% while FFA for stored control, K and MRB burfi increased from

0.46, 0.78 and 0.8 to 1.09, 1.15 and 1.10% respectively within 5 weeks of storage.


Page 179

This was due to entry of moisture as indicated by a marked increase of moisture in the

sweets. However this increase did not affect the sensory quality of the products. The

burfi and ladoo of pearl millet remained sensorialy acceptable during the entire one

month storage without any adverse effect on their acceptability by consumers,

whereas those of the traditional sweets, the overall acceptability scores decline after 3

weeks of storage.

Pearl millet flour is not stable during storage, as it develops disagreeable

sensory flavors. Hence, the millet flour was roasted prior to its use in these products.

Roasting stabilized lipids by inhibiting lipase activity in the pearl millet. Pearl millet

can be successfully used in preparation of sweets that is preferred by consumers.

Table. 4.42. Proximate Composition of Refined Wheat Flour (control) and

Pearl Millet Cookies

Cookies Moisture

(g %)

Fat

(g %)

Proteins

(g %)

Ash

(g %)

Iron

(mg %)

Calcium

(mg %)

Phosphorus

(mg %)

Control 2.57 b

±0.14 16.95 a ±1.21 6.80

a ±0.22 0.38

a ±0.02 2.48

a ±0.34 18.26

a ±0.16 86.76

a ±

5.4

K 0.58 a ±0.03 19.71 a ±1.09 8.63 b ±0.23 0.93 c ±0.05 6.39 b ±0.01 25.70 b ±0.54 208.10 b±10.2

MRB 0.34 a ±0.03 17.82

a ±0.22 8.50

b ±0.33 0.77

b ±0.02 6.71

b ±0.10 29.36

c ±0.54 189.99

b ±6.2

Means sharing the same superscripts are not significantly different from each other (Tukey’s

– B significant difference test, P ≤ 0.05), K – Kalukombu, MRB – Maharashtra rabi bajra.


Page 180

Data in Table 4.42 presents proximate composition and mineral content of the

cookies prepared out of refined wheat flour and pearl millet. The moisture content of

control cookies (100% refined wheat flour) was significantly (P ≤ 0.05) higher than

pearl millet cookies. This difference can be attributed to the use of roasted millet

flour. Higher moisture content of cookies results in a soggy and soft texture which is a

major cause for lower consumer acceptability. Fat content remained similar for

control and millet cookies. Cookies fortified with pearl millet was had significantly (P

≤ 0.05) higher protein, ash and minerals like iron, calcium and phosphorus.

Approximately 2.7 fold increase in the iron content was observed in pearl millet

cookies. Other minerals such as calcium and phosphorus increased by 1.6 and 2.2

times respectively in the pearl millet cookies.

Table – 4.43. Physical Characteristics of Refined Wheat flour (Control) and

Pearl millet Cookies.

Parameters Control Kalukombu MRB SEM

±

Diameter (mm) 88.0b 87.0a 86.7a 86.7

Thickness (mm) 10.6a 10.9

a 11.1

b 0.20

Spread ratio (D/T) 8.30b 7.98

a 7.81

a 0.10

Spread factor 83.01b 79.81a 78.10a 0.50

Breaking strength (g) 1600a 1650

b 1680

b 10

SEM – Standard error of means at 15 degrees of freedom, mean in the same row followed by

different superscripts differ significantly (P ≤ 0.05), MRB – Maharashtra Rabi Bajra.


Page 181

Physical characteristics of cookies such as diameter, thickness, spread ratio

and breaking strength were determined and are presented in Table – 4.43. The data

showed that the diameter of control, K and MRB cookies did not vary between each

other. Thickness of cookies prepared out of wheat flour (control) and K where similar

while that of MRB increased. Spread ratio is based on the values obtained for

thickness and diameter of the cookies. The spread ratio of the cookies decreased from

8.30 to 7.98 and 7.81 for K and MRB cookies respectively. Similarly, the breaking

strength values for control, K and MRB cookies were 1600, 1650 and 1680g

respectively indicating that the texture of the pearl millet cookies did not vary

between varieties. Pearl millet cookies had light and crisp texture.

OQ – overall quality, C – Control, K – Kalukombu, MRB – Maharashtra Rabi bajra

Figure 4.10. Sensory Profile of Wheat flour (Control) and Pearl Millet Cookies


Page 182

Research findings from a study on the influence of flour mixes on the quality

of gluten-free biscuits indicated that a mixture containing millet flakes was one

among the three best mixtures selected based on sensory data (Tilman et al 2003).

This shows that millets could exert beneficial influence on the quality of biscuits.

However, in a comparative study on sorghum cookies and pearl millet cookies, latter

were dark, less gritty and more fragile than the former (Badi et al 1975). A point to be

noted here is that there was a wide variation in the composition and relative

proportion of ingredients of the products studied, which, in all probability, resulted in

the diverse quality of the products. In the present study, control cookies had off-white

color and crisper texture. Perceptible vanilla – like aroma, baked cereal aroma and

sweet taste in control cookies were found to be low which consequently reduced its

overall quality (8.1). On the other hand, pearl millet cookies (K&MRB varieties) had

closely matching sensory profile (Fig. 4.10) which differed significantly from control

in key attributes such as color, vanilla-like aroma, baked cereal aroma and sweet taste.

Higher perceived intensities of these desirable sensory parameters significantly and

positively impacted the overall quality of pearl millet cookies rated at 10.7 for K and

9.2 for MRB respectively as compared to control (8.1). These finding indicated that

the pearl millet cookies were acceptable. Sensory panelists opined that pearl millet

cookies had a combination of desirable and lasting vanilla – like aroma coupled with

typical baked millet aroma. In addition, crisp and crumby texture was perceived in

these cookies which further enhanced their sensory appeal making them highly

palatable. High acceptability for pearl millet cookies in a similar study was reported

(Archana et al 2004) where depigmentation of pearl millet was carried out. Results

showed that native or pigmented pearl millet cookies were rated slightly less for the


Page 183

stated sensory attributes compared to depigmented cookies. However, in the present

study, it was found that dark color of the pearl millet cookies did not adversely affect

its acceptability, instead; it provided an interesting visual appeal.


Page 184


Page 185

C – Control, K – Kalukombu, MRB – Maharashtra rabi bajra,

Figure 4.11: Sensory Profile of Wheat Flour (Control) and Pearl Millet Cookies

as Affected by Storage


Page 186

Cookies prepared from wheat flour (control) and two pearl millet varieties (K

and MRB respectively) were storage in two different packaging materials for a period

of 12 weeks (Fig. 4.11) Cookies packed in PET-PP and foil packaging materials were

withdrawn fortnightly and subjected to sensory descriptive analysis. Results of

sensory analysis showed that experimental samples prepared using two pearl millet

varieties had better sensory quality compared to the traditionally prepared cookies

containing refined wheat flour, at the end of 12 weeks of storage.

Traditionally prepared cookies packed in PET – PP pouches were off-white in

color which turned pale brown during the course of storage. Initially, the samples

were crisp (6.2) in texture with slightly perceptible vanilla – like (4.3) aroma and

moderately intense baked cereal aroma, with an overall quality score of 8.1. During

subsequent withdrawals, perceptible decrease in crispness and loss of vanilla-like

aroma were observed. By the end of 4 weeks, perceptible ‘staleness’ and ‘rancid’

notes had developed. The trend continued with increasing intensity, rendering the

product ‘not acceptable’ with an Overall Quality (OQ) score of 6.1 at the end of 8

weeks.

Conventionally prepared cookies packed in foil showed a similar trend which

was just acceptable at the end of 2 weeks. However, by the end of 4 weeks, a sharp

decrease in crispness and increase in ‘stale’ and ‘rancid’ notes were observed in this

sample, which was reflected in reduced OQ score of 5.9 compared to 8.1 of initial

sample. Consequently, further sensory evaluation of these samples was discontinued.

Cookies from K variety, packed in PET-PP had initially higher scores for

crispness, vanilla – like aroma and baked cereal aroma resulting in a desirable high

overall quality score of 10.7. Slight textural changes were observed during the course


Page 187

of storage which was not significant. Color (brownish with black spots) and

appearance of the cookies remained the same throughout the study. However, a

perceptible and significant reduction in vanilla – like aroma and baked cereal aroma

was observed by the end of the study. Most notably, the cookies had no ‘stale’ and

‘rancid’ notes at the end of the study. The intensity of most of the desirable attributes

remained at satisfactory levels indicating that the product was acceptable with an OQ

score of 9.0 at the end of 12 weeks.

‘K’ cookies packed in foil showed a similar pattern but for better retention of

texture. However, loss of vanilla – like aroma was more drastic in this sample at the

end of 12 weeks. This effect was observed to be more pronounced after 8 weeks of

storage. No ‘stale’ or ‘rancid’ notes were perceived in this product. Samples were

found to be acceptable with an OQ score of 8.6 at the end of 12 weeks

Although there was a decrease in OQ compared to that of initial samples, this

may be attributed to slight loss of texture (crispness) and vanilla – like aroma.

Sensory profile of ‘MRB’ cookies stored in PET – PP pouches closely

matched that of ‘K’ cookies except for minor differences such as the former was less

crumbly and the latter had slightly higher baked cereal aroma at the end of 12 weeks.

There was no development of off – odors or off – taste in the product during storage.

The cookies were found to be acceptable within an OQ score of 9.0 at the end of

storage period, which was very close to that of initial sample.

‘MRB’ cookies packed in ‘Foil’ had sensory quality similar to that of its

counterpart packed in ‘PET – PP’. A feature repeatedly noted in this sample also was

better retention of texture (crispness) and baked cereal aroma. No perceptible ‘off –


Page 188

notes’ were observed in this sample by the end of 12 weeks. Overall quality of this

cookie (8.8) was close to that of initial sample (9.2).

On the basis of sensory data of cookies during storage, it may be concluded

that experimental cookies prepared using pearl millet had better sensory quality and

could keep well for 12 weeks compared to traditionally prepared sample containing

refined wheat flour. At the end of 12 weeks of storage, there was no significant

difference in the sensory quality of ‘K’ and ‘MRB’ cookies. However, ‘MRB’ cookies

had overall quality scores closer to initial samples compared to ‘K’ cookies. As a

packaging material, ‘Foil’ was a better option for better retention of crispness in

cookies. Although there was reduction in perceptible vanilla – like aroma in the

cookies by the end of 12 weeks, it did not adversely affect their overall quality scores.

There was no perceptible off – note in the experimental cookies. Both ‘K’ and ‘MRB’

cookies were acceptable and found to be highly palatable throughout the storage

study.


Page 189

Bars with different letters (a, b, c) differ significantly (P ≤ 0.05), MRB – Maharashtra rabi bajra.

Figure 4.12: Equilibrium Relative Humidity of Wheat Flour (Control) and Pearl

Millet Cookies as Affected by Storage


Page 190

Water content is one of the most important properties in the food domain.

Water is essential for growth and metabolism of microbes and many chemical

reactions that occur in the product. Water occurs in a food system in both free and

bound states. Free water supports the growth of microorganisms, chemical reactions

and acts as a transporting medium for compounds. Whereas bound water is tied up by

water soluble compounds such as sugar, salt, gums etc. The amount of water that is

available to microorganisms is termed as water activity (aw). Many microorganisms

prefer an aw of 0.99 to grow. Relative humidity and aw are related. Water activity

refers to the availability of water in a food or beverage. Relative humidity refers to the

availability of water in the atmosphere around the food or beverage. Equilibrium

relative humidity (ERH) is a valuable tool for food product packaging development as

it is an indicator of what chemical reactions may occur during distribution and of how

much packaging protection should be designed for the product to give it the required

shelf life. During storage, foods in the semi-moist rubbery state can become partially

crystalline as sugar is crystallized out as seen in milk based powders, soft cookies,

chocolates and cake glazes or they can harden by several different chemical reactions

including protein aggregation (Labuza et al 2004, Zhou et al 2008, Labuza et al 1970;

Barbosa et al 2007).

The relationship between moisture content and water activity of control and

pearl millet cookies stored at room temperature are presented in Figure 4.12. The

cookies were exposed to a wide range of water activities (0.31, 0.64 and 0.76) to find

out its effect on the texture. This was done by placing cookies in a petridish inside

desiccators containing various saturated solutions equilibrated at certain relative

humidities. The moisture content of the cookies was measured at weekly intervals up


Page 191

to 8 weeks using a moisture analyzer (Mettler Toledo, Switzerland). The initial

moisture content of control, K and MRB cookies were 2.57, 0.58 and 0.34%

respectively. The corresponding values increased to 2.90, 1.47 and 1.44% respectively

at an aW of 0.31 by the end of the 8th week. At 0.64 and 0.76 aW, pearl millet cookies

gained about 3.5% and 5% moisture while control cookies gained 4.4% and 5.4%

moisture respectively. Highest moisture gain in the control and pearl millet cookies

was seen when they were stored at a water activity of 0.64 and 0.76. Texture is an

important sensory attribute for many cereal based foods and the loss of desired texture

leads to a loss in product quality and a reduction in shelf life (Nielsen 1979). The

texture of cookies was altered by changes in the water activity due to moisture gain

resulting in loss of crispness or hardness. At the end of the study period (week 8)

cookies became softer and soggy. From the results, at an aW of 0.31, control and pearl

millet cookies were stable with respect to texture and mold growth. Thereafter,

cookies became soggy and lost its crispness due to moisture uptake associated with

increase in the water activity (0.31 to 0.72).


Page 192

Bars with different letters (a, b, c) differ significantly (P ≤ 0.05), MRB – Maharashtra Rabi bajra.

Figure 4.13: Moisture Content of Wheat flour (Control) and Pearl Millet Cookies

as Affected by Storage.


Page 193

Cookies prepared from wheat flour (control) and two pearl millet varieties (K

and MRB respectively) were packaged in two different packaging materials (PET –

PP and Foil) and stored for a period of 12 weeks. Cookies packed in ‘PET-PP’ &

‘Foil’ packaging materials were withdrawn fortnightly and analyzed for moisture,

peroxide value and free fatty acid.

The moisture content of the cookies is presented in Figure 4.13. Moisture

content is a marker of shelf life of a particular product. The initial moisture content of

control, K and MRB cookies were 2.57%, 0.46% and 0.34% respectively. The

corresponding values increased to 3.41, 1.00 and 1.31 after 12 weeks of storage in

PET – PP packaging material while, cookies packed in foil showed a marginal

increase in the moisture content. K and MRB cookies packed in foil exhibited lower

moisture content throughout the storage period retaining its crispy texture which is

associated with freshness and quality of a product, its loss might be a chief cause of

consumer rejection.


Page 194


Figure 4.14: Peroxide Value of Wheat Flour (Control) and Pearl Millet Cookies

as Affected by Storage


Page 195

The peroxide value of the cookies is presented in Figure 4.14. The peroxide

value is expressed as milli equivalents KOH /100g of fat. The data on peroxide value

of control, K and MRB cookies packed in PET – PP and foil respectively showed that

there was an increase in the peroxide value (PV) during the storage period of 12

weeks. The initial PV of control, K and MRB was 0.90, 0.92 and 0.92% respectively.

A higher content of PV was found in control cookies (6.55%), followed by K (1.87%)

and MRB (1.4%) packed in PET – PP, while, those packed in foil comparatively

showed a lower increase of 4.78, 1.2 and 1.1% respectively during storage period.


Page 196


Figure 4.15: Free Fatty Acid Content of Wheat Flour (Control) and Pearl Millet

Cookies as Affected by Storage


Page 197

The free fatty acids (FFA) present in the fat extracted from cookies are

presented in Figure 4.15. Free fatty acid content is one of the main criteria for

checking the quality of oil. The free fatty acid value is expressed as palmitic acid

equivalents /100g of fat. The cookies on fresh basis contained 0.23 and 0.24 FFA for

control and pearl millet. These values were comparable to the reported values (Aftab

et al, 2008). During storage, FFA content increased to 0.69, 0.46 and 0.40 for control,

K and MRB cookies packed in PET – PP, While, for cookies packed in foil, a minor

increase of 0.25, 0.3 and 0.24 respectively was seen. Cookies packed in PET – PP

showed a significant increase while those packed in foil had constant values through

the storage period. The level of FFA indicates a higher level of oil hydrolysis and

usually freshly processed edible oils contain less than 0.1% FFA. This indicated that

cookies packed in foil can be stored up to 12 weeks, without any apparent undesirable

changes.

Findings of the study demonstrated that complete/or partial replacement of

potentially low cost pearl millet flour improved the overall nutritional quality of the

prepared food products. A considerable increase in total iron, calcium and phosphorus

content as well as bioaccessible iron and calcium of dosa, roti, puttu prepared from

pearl millet was seen. Nutritionally important starch fractions of the breakfast items

prepared from pearl millet revealed low RDS and SDS with increased RS content.

The sensory scores of baked items (bun and cakes) prepared with 40% pearl millet

flour as well as traditional sweets (ladoo and burfi) and cookies prepared from 100%

pearl millet flours were in the acceptable range (6.6 – 7.8). The acceptability scores of

the stored traditional sweets and cookies packed in various packing materials

remained constant until the end of study period. Lower moisture, FFA and PV values


Page 198

of cookies packed in foil indicated that foil is a suitable packaging material for storage

of cookies up to 12 weeks or more without any apparent undesirable changes. Thus

the highly beneficial pearl millet could be a successfully used in the production of

value-added, nutritious convenience foods for the human consumption.

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