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CHAPTER II
PHYSICOPHYSICOPHYSICOPHYSICO----CHEMICAL, RHEOLOGICAL CHEMICAL, RHEOLOGICAL CHEMICAL, RHEOLOGICAL CHEMICAL, RHEOLOGICAL
PROPERTIES AND CHAPATI MAKING PROPERTIES AND CHAPATI MAKING PROPERTIES AND CHAPATI MAKING PROPERTIES AND CHAPATI MAKING
PROPERTY OF WHOLE WHEAT FLOURSPROPERTY OF WHOLE WHEAT FLOURSPROPERTY OF WHOLE WHEAT FLOURSPROPERTY OF WHOLE WHEAT FLOURS
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2.1. INTRODUCTION
Chapati, an unleavened baked product made from whole wheat
flour, is the staple diet of majority of the population of India and its
subcontinent (Haridas Rao et al, 1986). Whole wheat flour is mixed
with water into a dough and the dough is normally given a minimum
rest period of 15-30 min, before it is sheeted to a thickness of about 2
to 3 mm. The dough thus sheeted is cut into a diameter of 12 to 15cm
and baked on a hotplate at 220°C and finally puffed on a live flame for
few seconds. It is generally consumed hot along with other adjuncts.
Complete and full puffing, soft and pliable textures as well as
wheatish brown color with dark brown spots are some of the
important attributes of good quality chapati.
The quality characteristics of chapati are mainly governed by
the quality of wheat used and the processing conditions employed for
converting it into flour (Austin & Ram, 1971; Leelavathi et al, 1986).
Based on the physicochemical properties, flour having particle size
distribution of upto 1000µm give good chapatis (Islam & Johansen,
1987). Factors reported to influence the chapati quality are damaged
starch content and water absorption of the flour (Haridas Rao et al,
1986; Abrol & Uprety, 1970; Haridas Rao et al, 1989 & Haridas Rao,
1993). The visco-elastic property of dough, which influences the
baking quality of wheat, depends on the quality and quantity of
protein. Wheat varieties having 9.5 to 10.5% protein are found to be
suitable for the preparation of chapati (Austin & Ram, 1971).
However, there are reports to indicate that wheat having higher
43
protein contents (>12%) are suitable for chapati making, indicating
the importance of quality or nature of proteins present in wheat in
determining chapati making quality (Srivastava et al, 2003).
The objectives were as follows
1. Physico-chemical properties, rheological properties of whole
wheat flour and the overall quality of chapati prepared from
wheat cultivars used in this study.
2. To correlate the physico-chemical and rheological properties to
the overall quality of chapatis.
44
2.2. MATERIALS AND METHODS
2.2.1. Procurement of wheat
Ten aestivum wheat varieties namely GW-322, HD-2189, HD-
2781, HD-2501, K-9644, MACS-2496, NIAW-34, and NI-5439 were
procured from Agharkar Research Institute, Pune and DWR-162 and
DWR-39 were procured from University of Agricultural Sciences,
Dharwad, India, for the studies.
2.2.2. Kernel hardness
Wheat kernel hardness was measured using a Universal Texture
Measuring System (Lloyds, LR 5K, UK). Measurement for 20 grains
from each variety was taken and the average calculated. The kernel
hardness was measured using the following settings: cross head
speed–100 mm/min; pre-load-200 gf; compression-50% of sample
original height; probe diameter-10 mm. The load cell capacity-100 Kgf.
The results are expressed in Newtons.
2.2.3. Milling of wheat
Cleaned wheat was milled into whole wheat flour (WWF) in a
commercial disc mill (plate mill) to obtain whole wheat flour, which
would pass through 400µ mesh. The flour obtained was cooled and
sieved 2-3 times for homogenization.
2.2.4. Chemical analysis
Moisture, total protein, total sugars and damaged starch of WWF
were determined according to the standard AACC methods (2000).
Values reported are the average of triplicate determinations.
45
2.2.5. Rheological characteristics
Farinograph, Amylograph and Extensograph studies were
carried out according to standard AACC methods (2000).
2.2.6. Water absorption of chapati dough
Water absorption of whole wheat flour required to obtain
chapati dough of optimum consistency was determined using
Research Water Absorption Meter according to Haridas Rao et al
(1986).
2.2.7. Preparation of chapati
Chapatis were prepared from WWF according to Haridas Rao et
al (1986) with slight modifications. Chapati dough was prepared by
mixing 200g flour and water equivalent to chapati water absorption in
a Hobart mixer (Model N-50) at speed 1 (61rpm) for 3 mins. The dough
was divided into pieces of 50g each and sheeted to a thickness of 1.5
mm in a specially designed platform to maintain uniform thickness.
The sheeted dough was cut into a circular shape of 12 cm diameter
using a die. The sheeted dough was baked on a hot plate maintained
at 215ºC for 70 s on side one, and 85 s for side two. The chapati was
then transferred to a heated gas tandoor (370ºC) in such a way that
side one was placed on the grill and heated for 10 s. The puffed
chapati from the tandoor was cooled and evaluated.
46
Fig. 2.1: Dough sheeted to chapati.
Fig. 2.2: Sheeted chapati cut with die.
Fig. 2.3: Chapati baked in an oven.
47
Fig. 2.4: Chapati placed in gas tandoor for puffing.
2.2.7.1. Objective evaluation of chapati and dough
Height of the puffed chapati was measured as soon as the chapati
was removed from the Tandoor oven according to Haridas Rao et al
(1986). The texture of chapati was evaluated by using the texture
analyzer (Stable Micro Systems, Model TA-HD, UK) using the Warner
Bratzler blade (HDP/BSW). Three strips measuring 4 X 2 cm from each
chapati were cut. One strip at a time was placed on the center of the
sample holder and allowed the blade to cut the chapati strip. The force
(Kg) required to cut the chapati strip into 2 pieces was recorded. The
speed was maintained at 1.70 mm/s. Measurement for four chapatis
were recorded and average value of these is reported.
2.2.7.2. Subjective evaluation of chapati
Sensory evaluation of chapatis was done by a panel of judges
using a 10 point scale. The product was evaluated for its color,
appearance (color of the spots and their uniformity), tearing strength,
48
pliability, mouthfeel (soft, tough, leathery), and taste and aroma
(sweetish, wheaty, bland) according to Haridas Rao et al (1986).
2.2.8. Statistical analysis
The experimental data, including sensory scores of chapati were
treated statistically by Duncan’s new multiple-range test to determine
the significance of results (Steel & Torrie, 1980).
49
2.3. RESULTS AND DISCUSSION
2.3.1. Physico-chemical characteristics of WWF
Physico-chemical and rheological characteristics of whole
wheat flour (WWF) are shown in Table 2.1 and Table 2.2, respectively.
The damaged starch content in WWF, which is crucial for chapati
making quality (Haridas Rao et al, 1989) varied from 12.3% (MACS-
2496) to 17.6% (DWR-39). Damaged starch content of the flour is
related to the kernel hardness and severity of grinding (Bass, 1988).
Harder the wheat kernel, higher would be the damaged starch content
and vice versa. Since the same conditions were followed for the
grinding of wheat, the differences in the damaged starch content of
flour mostly was related to the hardness of wheat kernels (Fig 2.5). The
results showed that wheat varieties MACS-2496, K-9644 and GW-322,
which had relatively lower kernel hardness showed lower damaged
starch content and wheat varieties with relatively higher kernel
hardness mostly had higher damaged starch content. The kernel
hardness and damaged starch contents in different wheat varieties
showed good positive correlation (r=0.74, p<0.05). Haridas Rao et al
(1989) highlighted that WWF having damaged starch content in the
range of 14.1 – 16.5% yielded good quality chapatis. The total protein
content of WWF samples ranged from 11.6% (HD-2781) to 14.6%
(MACS-2496) (Table 2.1). Majority of the Indian wheat varieties are
generally reported to have protein contents ranging from 8 to 15%
(Saxena et al, 1997; Srivastava et al, 2003).
50
Table 2.1: Physico-Chemical Properties of Different Wheat Varieties
Wheat Varieties
Kernel hardness (Newton)
Moisture (%)
Total Protein
(%)
Damaged Starch
(%)
Falling Number
Sugars* (%)
SDS Sedimentation
Value
DWR-162 102.0c ± 9.3 7.2b ± 0.1 12.7a ± 0.2 17.1f ± 0.1 420d ± 10 1.17b ± 0.02 59c ± 1
DWR-39 112.0c ± 11.1 7.3b ± 0.2 12.3a ± 0.3 17.6f ± 0.3 461f ± 12 1.22b ± 0.03 62c ± 2
GW-322 78.9b ± 3.7 7.2b ± 0.1 13.3b ± 0.1 12.6a ± 0.1 406d ± 11 1.15b ± 0.02 52a ± 1
NI-5439 121.0c ± 8.3 6.9a ± 0.1 13.5b ± 0.1 16.2e ± 0.1 390c ± 15 1.16b ± 0.04 54b ± 2
NIAW-34 119.7c ± 14.1 7.1ab ± 0.1 13.7b ± 0.1 14.8c ± 0.1 440e ± 11 1.41a ± 0.02 55c ± 2
HD-2781 167.0d ± 11.4 7.2b ± 0.1 11.6a ± 0.2 15.3d ± 0.2 360b ± 12 1.39a ± 0.04 62c ± 3
HD-2501 111.0c ± 8.4 7.2b ± 0.1 12.7a ± 0.2 14.8a ± 0.1 486g ± 17 1.06d,c ± 0.02 52a ± 2
K-9644 77.2b ± 6.0 6.9a ± 0.1 13.3b ± 0.2 13.8b ± 0.3 598h ± 17 1.41a ± 0.06 52a ± 1
HD-2189 110.0c ± 5.8 7.6c ± 0.1 12.0a ± 0.3 16.3e ± 0.2 464f ± 12 1.01c ± 0.04 50a ± 2
MACS-2496 65.3a ± 4.3 6.7a ± 0.1 14.6c ± 0.2 12.3a ± 0.1 370a ± 14 0.84d ± 0.04 53b ± 2
Data reported are as-is basis and expressed as mean ±SD of three determinations. Mean of the same column followed by different letters are significantly different (p<0.05). *Sugars: Sum of reducing and non-reducing sugars.
51
Reducing and non-reducing sugar content in these ten varieties
ranged from 0.84% (MACS-2496) to 1.41% (K-9644, NIAW-34) (Table
2.1). Higher sugar content in WWF has been reported to impart
sweetish taste to chapatis (Leelavathi & Haridas Rao, 1988).
Fig. 2.5: Effect of kernel hardness on damaged starch content of whole wheat flour.
2.3.2. Rheological characteristics of WWF
Water absorption of WWF as measured in Brabender
Farinograph, varied from 69.9% (HD-2501) to 77.8% (DWR-162) (Table
2.2). The results showed that mostly, the flours having higher
damaged starch content also had higher water absorption, with few
exceptions. For example, WWF from MACS-2496 even though had the
lowest damaged starch content had relatively higher water absorption
value.
0
2
4
6
8
10
12
14
16
18
20
0
20
40
60
80
100
120
140
160
180
DWR-
162
DWR-39 GW-322 NI-5439 NIAW-
34
HD-
2781
HD-
2501
K-9644 HD-
2189
MACS-
2496
Dam
aged s
tarc
h (%
)Kern
el h
ard
ness (N
)
Wheat varieties
Kernel hardness (Newton)
Damaged Starch (%)
52
Table 2.2: Rheological Characteristics of Whole Wheat Flour from Different Wheat Varieties
Wheat Varieties
Farinograph characteristics*
Amylograph characteristics* Extensograph Characteristics*
Water
absorption (%)
Dough Stability
(min)
Gelatinisation temperature
(⁰C)
Maximum viscosity
(BU)
Cold paste viscosity
(BU)
Resistance to
extension (R) (B.U.)
Extensibility (E)
(mm)
Ratio R/E
DWR-162 77.8 2.8 67.7 470 581 435 112 3.9
DWR-39 75.5 2.5 67.3 530 728 425 108 3.9
GW-322 70.9 1.9 64.7 567 809 315 100 3.2
NI-5439 73.4 1.9 67.6 501 699 213 120 1.8
NIAW-34 76.2 1.3 66.0 479 690 560 108 5.2
HD-2781 76.0 1.5 63.6 478 658 315 116 2.7
HD-2501 69.9 1.8 66.1 527 691 220 122 1.8
K-9644 70.6 2.6 66.4 555 736 393 127 3.1
HD-2189 72.5 1.7 76.5 472 717 193 118 1.6
MACS-2496 74.9 2.9 75.8 480 763 595 96 6.2
* Average of two values.
53
This higher water absorption can also be due to higher protein
content in this variety. It is well known that besides starch, proteins
also influence water absorption of flour along with pentosans (Meuser
& Suckow, 1986). On the other hand, WWF from HD-2189 and NI-
5439 varieties even though had relatively higher damaged starch
content did not have comparatively higher water absorption values.
Gelatinization temperature ranged from 63.6ºC (HD-2781) to 76.5ºC
(HD-2189) on determining the amylograph characteristics. The GW-
322 wheat variety had the highest paste viscosity of 567 BU and cold
paste viscosity of 809 BU (Table 2.2).
Measurement of extensibility properties of WWF in Brabender
Extensograph indicated that resistance to extension (R) varied
between 193 B.U. (HD-2189) to 595 B.U. (MACS-2496) (Table 2.2).
The extensibility (E) properties of dough varied from 96 mm (MACS-
2496) to 127 mm (K-9644). The R/E ratio of these ranged from 1.6
(HD-2189) to 6.2 (MACS-2496). Ratio that indicates stiffness of the
dough, showed that varieties which had high protein contents viz.,
MACS-2496, NIAW-34 had relatively stiff dough. The total protein
content and dough stiffness were positively well correlated (r=0.72.
p<0.05).
2.3.3. Objective evaluation of chapati
Physical characteristics of chapatis prepared from ten wheat
varieties are shown in Table 2.3. The results showed that the puffed
height of chapatis varied from 4.7 cms (K-9644) to 5.5 cms (DWR-
162). The higher puffed height is said to be due to higher water
54
absorption of flour, which helps in generating sufficient steam for
puffing the chapati (Haridas Rao et al, 1986). Earlier it was noted that
WWF from K-9644 had relatively lower water absorption compared to
NIAW-34. On the other hand, other varieties namely, GW-322, HD-
2189, and HD-2501 even though showed relatively lower water
absorption, similar to K-9644, had relatively higher puffed height (Fig.
2.6).
Table 2.3: Chapati Making Properties of Whole Wheat Flour from Different Wheat Varieties
Wheat Varieties Puffed height (cms)
Cutting Force (N)
DWR -162 5.5c ± 0.12 5.8c ± 0.13
DWR - 39 5.3c ± 0.11 5.6c ± 0.12
GW - 322 4.9a ± 0.09 5.1b ± 0.41
NI - 5439 4.8a ± 0.08 5.4b ± 0.20
NIAW - 34 5.2b ± 0.13 5.5bc ± 0.18
HD – 2781 5.1b ± 0.08 7.0d ± 0.21
HD - 2501 4.9a ± 0.08 5.6bc ± 0.18
K – 9644 4.7a ± 0.09 4.2a ± 0.51
HD – 2189 5.1b ± 0.09 6.7d ± 0.15
MACS - 2496 5.0b ± 0.09 4.5a ± 0.58
Data reported are as-is basis and expressed as mean±SD of three determinations. Means of the same column followed by different letters are significantly different (p<0.05).
It is possible that, similar to bread, where gas retention
properties are governed by the visco-elastic gluten matrix, resulting in
higher loaf volume, the chapati dough should have a gluten matrix
which is capable of retaining more steam resulting in higher puffed
height. Haridas Rao et al (1986) reported that poor puffed height of
chapati is attributed to poor quality gluten. Fig. 2.7 shows chapati
puffed height verses protein content of WWF. Our studies showed a
55
poor negative correlation between protein content and puffed height of
chapati (r=-0.28, p<0.05).
Objective measurement of texture of chapati showed that
cutting force for chapatis ranged from 4.2 to 8.5 N (Table 2.3).
Chapatis made from NIAW-34 and HD-2189 had higher cutting force
values compared to chapatis made from other varieties. Austin and
Ram (1971) reported that good quality chapatis should give minimum
resistance to tearing. Haridas Rao et al (1986) reported that chapatis
made from flour with high protein content were chewy with high
tearing resistance and vice versa.
Fig. 2.6: Effect of water absorption on puffed height of chapatis.
In the present study, it was observed that WWF from K-9644
and NIAW-34 varieties, which have relatively less protein content (13.3
& 13.7%), required significantly higher cutting force. However, in
4.2
4.4
4.6
4.8
5
5.2
5.4
5.6
64
66
68
70
72
74
76
78
80
DWR -162 DWR - 39 GW - 322 NI - 5439 NIAW - 34 HD – 2781 HD - 2501 K – 9644 HD – 2189MACS - 2496
Puffe
d h
eig
ht (c
ms)W
ate
r absorp
tion
(%
)
Wheat varieties
Water absorption (%) Puffed height (cms)
56
relation to chapati making a protein content of 13.5% cannot be
considered as low. The variety, MACS-2496 which had relatively
higher protein content, required lower cutting force. Thus, the results
indicate that total protein content alone may not influence the cutting
force of chapatis, instead protein composition and other parameters
may have a role in chapati quality.
Fig. 2.7: Effect of protein content on puffed height of chapatis.
2.3.4. Sensory characteristics of chapati
Sensory evaluation scores of chapatis are shown in Table 2.4.
Chapatis prepared from wheat varieties DWR-162, DWR-39, NIAW-34,
GW-322, and NI-5439 had very appealing wheatish brown color with
uniform dark spots. On the other hand, color of chapatis made from
wheat varieties MACS-2496 and K-9644 was relatively darker.
Chapatis made from varieties HD-2501 and HD-2189 were not as
4.2
4.4
4.6
4.8
5
5.2
5.4
5.6
0
2
4
6
8
10
12
14
16
DWR -162 DWR - 39 GW - 322 NI - 5439 NIAW - 34 HD – 2781 HD - 2501 K – 9644 HD – 2189 MACS -
2496
Puffe
d h
eig
ht (c
ms)
Pro
tein
(%
)
Wheat varieties
Total Protein Puffed height (cms)
57
dark as the latter two varieties. Assessment of the tearing strength of
chapatis showed that DWR-162, DWR-39, GW-322 and NI-5439 had
higher scores. On the other hand, chapatis made from HD-2501 were
very fragile giving low scores. Sensory scores for the remaining
varieties were in-between those of the former two scores. However,
unlike in bread, where softer bread generally gets higher score, it is
not very easy to evaluate the required cutting or tearing strength in a
highly acceptable chapati. It is desired that chapati should not be too
fragile with easy to tear properties, but it should offer some resistance
to tearing as well as chewing. Chapatis made from wheat varieties
DWR-162, DWR-39, GW-322 and NIAW-34 were very pliable.
Leelavathi et al (1986) explained that higher water absorption capacity
of flour renders chapatis soft and pliable. However, in relative terms
the WWF from HD-2781 variety, even though had the highest water
absorption, produced chapatis that were relatively less pliable.
Highest sensory scores for taste and aroma were recorded for the
varieties DWR-162, DWR-39, GW-322 and K-9644. These chapatis
had wholesome sweetish aftertaste (Table 2.1).
The wheat varieties MACS-2496 and HD-2189 recorded
significantly lower scores for taste due to their bland taste. These two
varieties incidentally had relatively lower sugar content. It is possible
that the amount of sugar present in the flour even though is very
small, would enhance the wholesome taste in chapatis.
58
Table 2.4: Subjective Evaluation of Chapatis
Data expressed as mean ±SD, Mean followed by different letters in the same column box differ significantly (p<0.05).
Wheat Varieties
Appearance
(10)
Tearing strength
(10)
Pliability
(10)
Taste and Aroma
(10)
Eating quality
(20)
Overall quality
(60)
DWR – 162 8.6d ± 0.2 8.5c ± 0.3 8.4c ± 0.2 8.5d ± 0.3 18.4f ± 0.3 52.4c ± 0.4
DWR – 39 8.7d ± 0.3 8.5c ± 0.2 8.4c ± 0.3 8.5d ± 0.3 18.2f ± 0.6 52.3c ± 0.4
GW – 322 8.2c ± 0.5 8.6c ± 0.2 8.6c ± 0.3 8.3d ± 0.3 16.0e ± 0.4 49.7b ± 0.3
NI – 5439 8.2c ± 0.3 8.0b ± 0.2 7.8b ± 0.2 7.7c ± 0.3 16.6e ± 0.6 48.3b ± 0.4
NIAW – 34 8.8d ± 0.4 7.7b ± 0.5 8.1c ± 0.2 7.1b ± 0.2 14.6c ± 0.5 46.3b ± 0.4
HD – 2781 7.9b ± 0.2 7.4a ± 0.3 7.3a ± 0.5 7.9c ± 0.2 13.4a ± 0.2 43.9a ± 0.7
HD – 2501 7.7b ± 0.3 7.1a ± 0.5 7.4a ± 0.6 7.9c ± 0.3 14.6c ± 0.2 44.7a ± 0.5
K – 9644 7.1a ± 0.3 7.3a ± 0.2 7.9b ± 0.3 8.3d ± 0.5 15.2d ± 0.4 45.8a ± 0.4
HD – 2189 7.3a ± 0.3 7.7b ± 0.2 7.6a ± 0.4 6.5a ± 0.2 13.8a ± 0.5 42.9a ± 0.5
MACS – 2496 7.3a ± 0.3 7.4a ± 0.6 7.2a ± 0.3 6.2a ± 0.3 14.2a ± 0.9 42.3a ± 0.3
59
Sensory evaluation of chapatis for their eating quality properties
showed that DWR-162, DWR-39, NI-5439 and GW-322 had relatively
higher scores. These chapatis were neither tough nor hard to chew.
They were not weak, offering less resistance to chewing but had
optimum chewing properties. On the other hand, chapatis made from
varieties HD-2781 and HD-2189 were somewhat tough to chew, hence
had the least score. Objective measurement studies also showed that
chapatis made from these two varieties had high cutting force values
(Table 2.3). Chapatis made from K-9644 also had good chewing
properties.
Evaluating the overall quality of chapatis, it is clearly seen that
the varieties DWR-162, DWR-39 and GW-322 produced highly
acceptable chapatis. This was closely followed by those prepared from
NI-5439 and NIAW-34. It is important to note here that chapatis made
from K-9644 scored less, only for their dark color while they had
excellent pliability and eating qualities. Among the ten varieties tested,
MACS-2496 had the least overall score, mostly because of its bland
and insipid taste, undesirable texture and color and poor pliability.
Earlier, Srivastava et al (2003) reported that varieties NI-5439, NIAW-
34 grown, in a different geographical location, did not show good
chapati making properties. The protein and damaged starch contents
reported for were 11.4 and 12.8% for NI-5439 and 15.1 and 13.9% for
NIAW-34, respectively. In the present study, these values are different
and the damaged starch content was found to be higher for these
varieties. On the other hand, varieties, MACS-2496 and HD-2189 had
60
shown poor chapati making properties in both studies (Table 2.1).
Thus, the variations in the chemical and chapati making properties of
these varieties may be due to variation in soil and environmental
conditions as they were grown in different geographical locations.
Earlier, reports indicate that agronomic measures such as nitrogen or
sulfurfertilization, climatic conditions such as rain fall, temperature
and other factors do affect bread making quality (Kolster & Vereijken,
1993).