physico-chemical properties of sugar syrup produced …

International Research Journal of Applied Sciences, Engineering and Technology

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Official Publication of Center for International Research Development Double Blind Peer and Editorial Review International Referred Journal; Globally index

Available www.cird.online/IRJASET: E-mail: [email protected] pg. 21

PHYSICO-CHEMICAL PROPERTIES OF SUGAR SYRUP PRODUCED

FROM TWO VARIETIES OF YAM USING MALTED RICE AND MALTED

SORGHUM

Okafor D.C1, Chukwu, M. N2., Agunwah, I. M1., Aneke, E. J1. and Odoemena, C. M1 1Department of Food Science and Technology, Federal University of Technology, Owerri, Nigeria.

2Department of Food Technology, Abia State Polytechnic, Aba, Abia State, Nigeria

Corresponding Author: Okafor D.C

Abstract: Physico-chemical properties of sugar syrup produced from two varieties of yam using malted rice and malted sorghum were

studied. Yam varieties (Dioscorea dumetorum and Dioscorea alata) were used as a major source of starch in the production of syrup.

The yam varieties were dried, milled and sieved. Two sorghum varieties (White sorghum FaraFara and Red sorghum KSV8) and rice

(rice faro 60 variety) were malted, dried, milled and blended into the yam flour as source of enzyme. The yam flour with malted

sorghum and malted rice flour was used for the syrup production. Six types of sugar syrups were produced in the following

formulations; malted sorghum (white fara-fara) and yam (Dioscorea dumetorum), malted sorghum (Red KSV8) and yam (Dioscorea

dumetorum),malted sorghum (white fara-fara) and yam (Dioscorea alata), malted sorghum (Red KSV8) and yam (dioscorea alata),

malted rice (Faro 60) and Dioscorea dumetorum, malted rice (Faro 60) and Dioscorea alata were represented as MS1+Y1; MS1+Y2;

MS2+Y1; MS2+Y2; MR+Y1 and MR+Y2. The syrup from the blended samples had more amylose content than the 100% yam

syrups. Viscosity was observed to decrease in the yam syrup with addition of malted sorghum and malted rice. The sugar

concentration result of the syrup revealed that fructose ranged from 3.49% to 4.75%. Glucose was at the range of 7.27% to 8.54%.

Sucrose concentration was at the range of 17.47% to 18.54%. The findings showed that the syrups had more sucrose concentration.

The dextrose equivalent values were at the range of 34.48% - 37.49%. The syrups were of low quality owing to the levels of sugar

concentrations and dextrose equivalent observed.

Keywords: Yam flour, dextrose equivalent, sorghum, rice, syrup, sugar

1. Introduction

Yam is the common name for some plant species in the genus

Dioscorea that form edible tubers. The most economically

important ones are white yam (Dioscorea rotundata), yellow

yam (Dioscorea cayenensis), winged or purple yam (Dioscorea

alata), bitter yam (Dioscorea dumetorum), etc (Calverly, 2003).

Bitter yam and purple yam is gradually going into extinction as a

result of underutilization, this is as a result of the anti-nutritional

properties they possess, but are good sources of protein, lipid,

crude fiber, starch, vitamins and minerals, they also contain anti-

nutritional substances like total free phenolics, tannins, hydrogen

cyanide, total oxalate, amylase and trypsin inhibitors but it can

be inactivated by moist heat treatments and soaking followed by

cooking before consumption (Shajeela et al., 2011).

Syrup is a thick, sugary liquid made by boiling down or

otherwise concentrating plant sap, juice or grain extracts. It can

also be defined as a thick, sweet, sticky liquid, consisting of a

sugar base, natural or artificial flavourings and water (Tester et

al., 2004). Sugar syrup can also be defined as a concentrated

aqueous solution of glucose, maltose and other nutritive

saccharides from edible starch. It may also be any liquid


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hydrolasate of monosaccharaides, disaccharides or

polysaccharides and can be made from any source of starch such

as yam, potatoes, cassava and cocoyam. It may be produced by

dilute acid hydrolysis or enzyme hydrolysis of starch (Hull,

2010; Akpa, 2014).

High sugar syrup has characteristics such as low hygroscopicity,

low viscosity, and high resistance to crystallization, low

sweetness, reduced browning capacity and good heat stability.

These properties make it useful in many applications in the food

and pharmaceutical industries. In breakfast cereals, it is used to

improve shelf life, enhance flavour, reduce breakage and

maintain crispiness. It is also used to control crystallisation and

sweetness in ice creams and lollies whilst at the same time

providing body strength to these products. When used in

confectionery products, it helps to lower hygroscopicity of the

product, controls crystallisation, prevents drying and lowers

viscosity (Goyal et al., 2005). Sugar syrup is also very useful in

the manufacture of frozen fruits, liquors and crystallised fruits

and in brewing. It is also used as a thicker, sweetener and

humectant. It also provides a less expensive alternative for use in

candies, soft drinks and fruit drinks to help control production

costs. It can also be used as fermentation agent. The production

of sugar syrups provides as means of reducing the bulk density

of starch slurries. Sugar syrup is easier to handle than granulated

sugar (Agrawal et al., 2005).

Sugar syrup was the primary corn sweetener in the United States

prior to the expanded use of its production. Sugar syrup is also

used as part of the expanded use of its production (Muralikrishna

and Nirmala, 2005). Sugar syrup is also used as part of the

mixture that goes into creating fake blood for film and

television. Blood mixtures that contain sugar syrup are very

popular among independent films and film makers because it is

cheap and easy to obtain. Starch is required for the production of

low molecular weight products (glucose/dextrose, maltose,

maltotriose and dextrin) is widely applied in sugar, spirits, textile

as well as brewing (Mobini-Dehkordi and Javan, 2012).

The starch-degrading enzyme, alpha amylase (1, 4-α-D-

glucanohydrolase, E.C. 3.2.1.1) is widely distributed in nature.

This extracellular enzyme hydrolyses α-1,4 glycosidic linkages

randomly throughout the starch molecule in an endo-fashion,

producing oligosaccharides and monosaccharides including

maltose, glucose and alpha limit dextrin (Nigan and Singh,

2011). Alpha amylase is a monomeric, calcium binding

glycoprotein. Its single polypeptide chain has 496 amino acid

residues with four disulfide bridges. The alpha amylases belong

to glycosyl hydrolase family 13, which also include pollulanase,

iso-amylase, and cyclodextrin glycosyl transferase. These

enzymes are highly homologous in structure consisting of two

distinct domains. Domain A contains the catalytic site

surrounded by a (β/α) 8-barrel that was first discovered in

triosephosphate isomerase (Janecek et al., 1997). Domain B is

composed of a complex loop of varying length inserted between

β strand 3 and α helix 3 of the (β/α) 8-barrel. The functional

diversity and stability of different enzymes may be attributed to

domain B. Al1 alpha amylases share eight conserved residues

and seven of these residues are located at the active site of the

catalytic (β/α) 8-barrel.

Two X-ray structures have been determined for cyclodextrin

glycosyltransferase in complex with an intact substrate, and the

other with a covalently bound intermediate. The study provides

more definite proof for the α-retaining mechanism used by all

the enzymes in the α-amylase family. The activity and stability

of α-amylase are affected by temperature, pressure, pH, substrate

concentration, and additives (Fitter et al., 2001). According to

Wiseman 1987, alpha amylase has an isoelectric point of 5.4,

excellent pH and temperature of enzymatic activity at 4.7 and 55 oC respectively. Optimal temperature for alpha amylase has been

reported from 40 oC – 60 oC; while in the presence of calcium

ion, it was increased to 75 oC. The optimal requirements for the

activity and stability of alpha amylase vary with the enzyme

source.

Alpha amylases are found in most organisms that require the

conversion of stored or ingested carbohydrate. They are

widespread among higher plants, animals and microorganisms

(Kumar et al., 2009). Alpha amylase has been derived from

several fungi, yeasts and bacteria. However, enzymes from

fungal and bacterial sources have dominated applications in

industrial sectors (Gupta et al., 2003). In animals, the main

sources of the enzyme are: the salivary gland and the pancreas,

whereas in plants, alpha amylase is most often associated with

seed germination.

Alpha amylases are one of the most important and widely used

enzymes whose spectrum of application has widened in many

sectors such as clinical, medical and analytical chemistry. The


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most widespread applications of α-amylases are in the starch

industry, where they are used in the hydrolysis of starch into

fructose and glucose syrups (Nielsen and Borchert, 2000).

Beside their use in starch saccharification, they also find

application in food, baking, detergent, textile, and paper,

brewing and distilling industries. For instance, alpha amylase is

employed in the milling and baking industry to hydrolyse starch

to smaller carbohydrate, so as to reduce the dough viscosity and

increase sugar levels, prolong freshness, improve softness and

crust quality. Similarly, in the brewing and beverage industries,

alpha amylase is employed in mash thinning, improving runoff

of wort and the general quality of the end product. The

sweetener and confectionery industries (Alvin et al., 2002) have

used alpha amylase to control the ratios of different saccharrides

to achieve specific product qualities (Gupta et al., 2003). These

enzymes are used in detergents for laundry and automatic

dishwashing to degrade the residues of starchy foods such as

potatoes, gravies, custard, chocolate, etc. to dextrin and other

smaller oligosaccharides (Mukherjee et al., 2009).

Malted cereals have been used as sources of starch-hydrolyzing

enzymes, due to the fact that germination induces the synthesis

of hydrolytic enzymes (Obatolu, 2002). Malting forms a critical

stage in the production of cereal-based beverages in which

amylase and proteases inherently embedded in the cereal grain

are activated for the purpose of hydrolysis of starch and protein

into sugars and amino acids respectively. Evans et al. (2003)

reported that alpha amylase is synthesized during cereal

development and stored in matured endosperms. Alpha-amylase,

as other amylases, increase markedly during germination. It has

been shown that alpha amylase yield will peak within 3 - 4 days

of cereal germination (Egwim and Oloyede, 2006). Amylase

activity is a good predictor of diastatic power (DP) which is

required in brewing processes and an important characteristic for

estimating the quality of malt for beer production (Evans et al.,

2003).

Sprouting cereals appear to be one of the popular sources of

industrial amylase for some developing economies. Amylase

obtained from cereals during malting is the main enzyme

employed in enzymatic saccharification of starch in most starch-

based industries in Nigeria. Such industries include breweries,

pharmaceuticals, distilleries etc. The major cereals employed in

Nigerian industries are maize, sorghum and millet (Egwim and

Oloyede, 2006). Local and unpopular cereals may also be a close

alternative. Sorghum was shown to have higher germination

capacity than other cereals such as maize and rice. Before now,

sorghum alpha amylase was shown to be the closest alternative

to imported alpha amylase for industrial purposes (Egwim and

Oloyede, 2006).

Three tropical cereals malted and unmalted have been

recommended for use in the Nigerian brewing industry:

sorghum, maize and rice. Concerted efforts have been put in

place towards finding a possible substitute to barley (Iwouno and

Odibo, 2015). Basically, tropical cereals such as sorghum,

millet, maize and rice have all been malted for beer production.

Among these, sorghum has been much studied as a replacement

for barley, at experimental and industrial levels (Iwouno and

Ojukwu, 2012). However, maize has been used since time

immemorial as part of the carbohydrate material in beer

brewing, but mainly as an adjunct prepared in different forms

such as flakes, grits and flour. Malting of maize for use as a

major source of hydrolytic enzymes required for brewing

purposes has received less attention (Eneje et al., 2004). Malting

reduces the paste viscosity of slurries from cereal flours and

thereby raises the caloric density of the slurry which is highly

desired in weaning food formulations (Iwouno and Ojukwu,

2012). Moreover it is controlled germination process, which

produces a complement of enzymes, which are able to convert

cereal starch to fermentable sugar to secure adequate supply of

amino acids and other nutrients for yeast, and to modify the

quality of the microelements (Ikujenola et al., 2007).

Unfortunately, most of the Nigerians sources of starch have not

been used in syrup production. Apart from creating variety and

convenience, syrups from our local starch sources offer the

opportunity of adjusting flavour, colour, viscosity defects and

correcting product composition. Besides, as the consumer

demand for safe, stable and fresh-like products continue to

increase, it becomes necessary to develop acceptable fresh-like

and shelf-stable syrup that will satisfy the consumer’s demand.

Though, some research works have been done on the use of

starch extracts from cereals and tubers (only pure extracted

starch from cereal and tubers) in syrup production, there is little

of no information on the use of crude starch (whole nutrient

components or composition of the starch source) in syrup


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production and hydrolysing the crude starch using crude enzyme

sources.

The main objective of this research project is to produce sugar

syrup from two varieties of yam (Dioscorea alata and Dioscorea

dumetorum) using enzymes from malted rice and sorghum. The

specific objectives of this research project are the evaluation of

the effects of crude enzymes from malted rice and sorghum on

the hydrolysis of two varieties of yam flour used for the

production of sugar syrup without the use of exogenous enzymes

and the determination of the physico-chemical properties of the

syrup produced.

The success of this research will help provide a guide for the use

of crude/inherent enzymes present in the malting of cereal crops

(Oryzae glaberrima) for rice and (Sorghum bicolor and Sorghum

vulgare) for sorghum and dry milling of tuber crops (yam) in the

production of high quality sugar syrup .This will lead to the

industrialization of using crude starch for the production of sugar

syrup to a large extent. Production of sugar syrup which is

cheap, nutritious, wholesome and generally acceptable by the

consumer would be elaborated in the course of this study.

2.0 Materials and Methods

2.1 Collection of Raw Material

The yam tubers (Dioscorea alata and Dioscorea dumetorum),

rice (Orzyzae gabrielima) and Sorghum bicolor (White-Fara and

Red KSV8) used in this work were gotten from the Root and

Tuber Crops Research Institute, Umudike and Cereals Research

Institute, Umuahia, Abia State, Nigeria.

2.2 Preparation of Yam Flour

The yam flour was produced according to the method described

by Subramanian et al. (1992), where each sample of fresh yam

tubers as well as the sprouted yam tubers of Dioscorea

dumetorum and Dioscorea alata was peeled, washed and sliced

into chips. The yam chips were sun dried for 6 hours after which

they were oven-dried at 70 oC for 30 minutes using an electric

single oven (model: LRE4211ST). The drying continued until

the weight did not change significantly between two weighing

successions. The dried yam chips were then milled and sieved to

obtain fine flour (0.8mm sieve) as shown in Figure 1.

2.3 Production of the Malted Rice

One variety of rice by name FACO 60 (Orzyze gabrielima) was

used as one of the sources of enzyme for starch hydrolysis. The

rice was washed and soaked in water/steeped for 42 hours and

the water was changed every 6 hours interval. It was spread on a

jute bag in an air tight room for sprouting to commence. Water

was sprinkled every 6 hours interval on the grains to enhance

sprouting. It was germinated for 5days. The sprouted grains were

sun dried for 5days and were milled to get the rice flour (Figure

2).

2.4 Production of Malted Sorghum

The Sorghum bicolor varieties (White-Fara and Red KSV8)

were also malted for enzyme development for the production of

the syrup. It served as the second source of crude enzyme for

enzyme hydrolysis of the flour for syrup production (Figure 3).

2.4.1 Steeping: The grains were soaked in water to raise the

moisture content. Increasing the moisture content wakes the

grains up from dormancy and starts the process of growth. It was

steeped for 24 hours and spread on a jute bag in an air-tight

room for 1 day.

2.4.2 Germination: After the desired moisture content has been

reached, the grain was removed from the steep and spread on the

jute bag and it was kept in a dark, humid room to germinate.

During germination the grain starts to grow, breaking down the

grain structure and develops the enzymes. The grain started

sprouting within 10hours of the steeping sprouting and was fully

sprouted within 24 hours. Drying it was sundried for 3 days and

milled to get the sorghum flour from both varieties.

2.5 Production of Glucose syrup

The enzyme conversion process used for the glucose syrup

production was developed by modifying the processes described

by Nwanekezi et al. (2004). About 30 grams batches of yam

flour (crude starch) from different varieties was transferred into

150ml of water in a beaker and 15g of malted sorghum flour and

15g of malted rice flour as source of the alpha amylase enzyme

were added separately. After the slurry was made, calcium

hydroxide was added to the slurry to adjust the pH to 6.0-6.4.

The contents of the beaker was stirred continuously in a

magnetic heating stirrer as the temperature was raised to 80oC

and maintained at this temperature for 60min. Conversion of

starch in the medium was evaluated by adding 2 drops of iodine

solution on about 2ml of the sample poured out on a white

ceramic tile. A negative test for starch indicated that all the

starch had been hydrolyzed. After hydrolysis the liquor was


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boiled for 30m in and filtered across a double-layered muslin

cloth (Figure 4).

2.5.1 Concentration of yam glucose syrup

The filtrate (sugar solution) obtained above was concentrated in

a vacuum flask connected to a vacuum pump. The temperature

of the solution was maintained at 65oC throughout the

concentration process until the solution was 50% total solids.

2.5.2Analysis of the Glucose Syrup

2.5.2.1 Dextrose Equivalent (DE)

The determination of the dextrose equivalent (DE) was done

according to the Lane and Eyon method as reported by Smith

(2001). The dry solids obtained as described above were used for

this determination as follows:

Eight grams of the sample was weighed out and transferred

quantitatively with the aid of hot distilled water from a wash

bottle into a 200ml volumetric flask and was filled to the 200ml

mark. It was made up to the mark after it had cooled. A 25ml of

the sample was poured into a conical flask and brought to boil

over an open flame. The Fehling’s solution was titrated with the

sample to within 0.5ml of end-point. The flask was swirled and

the content boiled for 2 min. Then 2 drops of methylene

indicator was added and 2 drops of the sample solution was

quickly added, again it was brought to boil and the brick-red

copper oxide was allowed to settle at the bottom of the flask and

the supernatant liquid was observed. The sample solution was

continuously added drop-wise until one additional drop

completely removed the blue colour from the supernatant liquid

(Smith et al., 2005). The percent reducing sugars K and dextrose

equivalent DE were calculated thus:

K =200 × 𝐹𝑒ℎ𝑙𝑖𝑛𝑔′𝑠 𝐹𝑎𝑐𝑡𝑜𝑟 ×100

𝑆𝑎𝑚𝑝𝑙𝑒 𝑇𝑖𝑡𝑟𝑒 (𝑚𝐿)× 𝑆𝑎𝑚𝑝𝑙𝑒 𝑊𝑒𝑖𝑔ℎ𝑡 Equation 1

DE = 𝐾 ×100

%𝐷𝑟𝑦 𝑆𝑜𝑙𝑖𝑑𝑠

Equation 2

Where Fehling’s factor = 0.12

2.5.2.2 Measurement of apparent viscosity of glucose syrup

from yam flour

A Brookfield Synchro-electric rotational viscometer LVF model

(Brookfield Engineering laboratories Inc. Stoughton, MA, USA)

was used for the apparent viscosity measurement. The

measurements were done at room temperature (28 oC ±0.5 oC)

with spindle number 2. The viscometer probe bearing the spindle

was immersed in a beaker containing 250ml of the sample and

was made to share the samples at different spindle rotational

speeds (shear rates) set at 6, 12, 30 and 60 revolutions per

minute (rpm) and at different concentrations (10%, 20% and

30%). The viscometer dial readings were converted to

centipoises (mPa.s) by using Brookfield conversion charts (Sun

et al., 2010).

2.5.2.3 pH measurement

The pH was measured using a pH meter, Analog Beckman

Zeromatic SS-3 Magnetic stirrer with Teflon coated magnetic

bar standardized with buffer solution of 4.0 and 7.0 as described

by AOAC (2005). The pH meter was calibrated. The electrode

was rinsed with deionized water and wipe dry. The electrode

was dipped in buffer 7 solution and calibrated using the

standardized knob. The electrode was rinsed and dried before

dipping in buffer 4 solution. Again the electrode was rinsed and

when not in use placed in the clean storage solution (Onwuka,

2018).

2.6 Evaluation of sugars using high performance liquid

chromatography

The evaluation of sugars using HPLC generally followed the

process described in AOAC, 2006.

2.6.1 Sample Preparation and HPLC Analysis

A 5g portion of each sample was placed in a separate 200-ml

beaker with the addition of 40ml deionized water. It was stirred

on a magnetic stirrer for one hour and 10ml of 0.3M copper

sulfate were added while stirring was on. After stirring, the pH

was adjusted to 6.4 using 50% sodium hydroxide and a pH

meter. The sample was carefully transferred to a 200ml

volumetric flask and it was made up to the 200ml mark with

deionized water. It was thoroughly mixed. The sample was

filtered through Whatman 2V filter paper overlaid with 0.5g

acid-washed celit (to aid filtration) into a 5-oz plastic cup with

cap. It was placed on a Sonicator for 2.5h for vortexing.

Vortexing of the sample vials for every 10 to 15 min was

performed until no residue was found on the wall of the vials.

Filtration into a 2-ml injection vial using syringe and 0.2 μm

nylon filters was done to get the clear solution ready to be

analyzed against reference standards using HPLC.


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The use of the HPLC system to identify and quantify the sugars

involved the comparison of each peak retention time and area

with those of the standards. A standard curve for each sugar was

prepared by injecting different sugar standards (glucose, starch,

raffinose, sucrose, dextrose, lactose, stachyose, galactose,

fructose, xylose and maltose). The HPLC system was

conditioned by flushing with deionized water for 3h, flushing

with pure acetonitrile (or HPLC grade isopropanol or propan-2-

ol when it became difficult) for 3h and deionized water until it

was cleared of detectable materials before chromatography was

performed. Calibration standards and samples were analyzed by

HPLC with refractive index detector using the following

conditions: Mobile phase: 7:3(v/v) acetonitrile/water; Flow rate:

1.0ml/min.; Column temperature: ambient; Elution mode:

isocratic, Run time: 25 min.; Injection volume: 75μl. A run is

composed of 55 to 60 injections, including replicate samples,

standards and a minimum of 10% quality assurance samples,

validated control samples, or recoveries. The analysis was done

in duplicates. The HPLC analysis was done based on AOAC

Official Method 982.14 (2006).

2.7 Determination of total dissolved solids (TDS)

The total dissolved solids of the samples were determined using

a total dissolved solids meter (ATP Instrumentation–TDS-5031-

Meter High range. ATP Instrumentation, UK.). The instrument

probe was inserted into a beaker containing the sample and

allowed for a few minutes until the reading equilibrated (Baxter,

2017).

2.10 Statistical Analysis

Triplicate data obtained were subjected to statistical analysis

using SPSS software of version 21. Mean values were

determined and ANOVA was done as well as Fisher’s Least

Significant Difference (Pallant, 2004) was used to determine for

the separation of the means at (p≤0.05).

3.0 Results and Discussion

3.1 Physico-Chemical Properties of Sugar Syrup Produced

3.1.1 pH

Table 1 presents the pH values of the yam syrups which revealed

that the pH of formulations had significant difference at p≤0.05.

The pH value of the syrups was in the range of 5.03–5.17. The

syrup with the highest pH value (5.17) was MR+Y1 syrup while

MS2+Y1 syrup had the lowest pH value (5.03). The slight

acidity of the experimental syrups indicates that the syrup is not

a pure solution of sugars, but a complex compound containing

minerals and organic acids (Ebonugwu, 2011). Stuckel and Low

(1996) obtained a higher pH value for maple syrup (6.20 to 7.90)

in comparison with what was obtained in this research. The

result obtained in this study was, however, in support with the

findings by Pancoast and Junk (1980) who reported pH range of

4.00 to 5.50 for glucose syrup. The results of the pH were

however; lower than the values of 5.65-6.5 reported by

Dziedzoave et al. (2004). The acidic nature of the syrups could

be attributed to the presence of organic acids which can function

synergistically with sugar to prevent spoilage (Pinto, 2009).

However, the low pH values will help effectively to control

and/or maintain the storage stability of the syrup at a longer

period of time. Acids present in foods do not only improve its

palatability, but also influences their nutritive value. The acid

influences the flavor, brightness of color, stability, consistency

and keeping quality of the product (Dziedzoave et al., 2004). It

could be deduced that the slightly low pH values of the syrup

formulations will effectively aid to maintain stability of colour

of the syrups during prolong storage period and impact slight

sourness to the product.

3.1.2 Density

Density of the syrups presented in Table 1 was found to be

significantly different (p<0.05). Densities of the syrups were in

the range of 1.45g/ml (MS1+Y1 syrup) to 1.49g/ml (MR+Y2

syrup). Dziedzic (2012) observed lower density in maple syrups

which ranged from 1.318 – 1.333g/ml. The difference in the

density of the syrup samples could have resulted from varying

rate of agglomeration of the gelatinized starch of the different

formulations during heating. Density is an indication of the

porosity of a product which influences package design. Density

is a measures the heaviness of the product (Onwuvuariri, 2004;

Adejuyitan, 2009). The higher the density, the heavier the

product and vice versa. Therefore, it could be inferred that syrup

from MR+Y2 having the highest density that can fit into a

particular container than those from the other formulations.

3.1.3 Dextrose Equivalent (DE)

Table 1 showed that formulation effect on dextrose equivalent of

the syrup samples was significant at p≤0.05. The dextrose

equivalents of the syrups were within the range of 34.48–

36.65%. Syrup from MS1+Y1, malted sorghum (white Fara-

Fara) + Dioscorea dumetorum had the highest dextrose


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equivalent of 36.65% and then MR+Y2 malted rice (Faro 60) +

Dioscorea alata had 36.57%. The least dextrose equivalent

(34.48) was observed in the syrup made from MR+Y1, malted

rice and Dioscorea dumetorum syrup. This is probably because

the starch composition of the malted rice and Dioscorea alata is

more in amylopectin than amylose. Making the substrate more

indisposed to enzyme hydrolysis, while the starch composition

of malted sorghum (white Fara fara) and Dioscorea alata is

more in amylose. That is, using the enzyme amylase in the

malted sorghum and rice hydrolysed it more readily to higher

dextrose equivalent 36.65%. Syrup with nominal value of DE =

0 implies that it has undergone 0% hydrolysis whilst 100%

hydrolysis means DE = 100. The DE obtained in this study

showed that the starch of the raw materials was partially

hydrolysed. Sigma (2005) stipulated DE of 16-20 for

maltodextrin syrups and DE of 30-100 for glucose syrup. The

value of DE found in this study confirmed that the product is

yam glucose syrup 30<DE<40. In comparison with a similar

work conducted by Ebonugwu (2011), the DE range (95.40 –

98.53%) reported by the author was higher than the DE range

obtained in this present study. Sigma (2005) showed that the

relationship between DE and the degree of sweetness of dextrose

equivalent indicates percent reducing sugars (fructose and

glucose) expressed as dextrose on a dry basis (Osuji and Anih,

2011). Therefore, the higher the DE the sweeter the syrup and

higher reducing sugars. Syrup sample made from MS1+ Y1 is

assumed to contain more of these non reducing sugars in

comparison with other syrup samples analyzed in this study.

3.1.4 Amylose content

The amylose content of the syrup samples from yam, sorghum

and rice formulations is shown in Table 1. The amylose content

showed significant difference among the syrups samples at

p≤0.05. Amylose content of the syrups was in the range of 4.77-

5.56%. Syrup made from MS1+Y1 was significantly the highest

in amylose content which was followed by syrup from MS1+Y2

(5.35%) and then MR+Y2 (5.26%).

3.1.5 Viscosity

Table 1 showed significant difference in the viscosity of the

syrups (p<0.05). Viscosity of the syrup samples was at the range

of 960.34 to 980.35cP. It was observed that the syrup sample

made with MS2+Y1 was more viscous than the rest of the syrup

samples which was followed by MS1+Y1 (980.25cP) and

MR+Y2 which shared same viscosity value of 960.34cP, MS 1+

Y 2 (960.37cP) and MR + Y1 (960.46cP) had no significant

(p<0.05) different between them. There is no significant

difference in syrup samples formulated with malted sorghum

(white Fara fara) and Dioscorea dumetorum. The result indicates

that blending malted sorghum with D. dumetorum would yield

syrup with higher viscosity. Viscosity is the measure of fluid

friction which can be considered as the internal friction resulting

when a layer of fluid is made to move in relationship to another

layer. Higher viscosity of syrup from malted sorghum and D.

dumetorum blends would be beneficial in production of high

viscous food products. High viscosity is mainly attributed to the

part that starch and enzyme were not extracted from the crude

sources before syrup production commenced. The results

obtained in this study were lower than the viscosity (2300cp-

2480cp) reported by Ahure and Ariahu (2013). This could be as

a result of the starting raw material, enzyme used, or method of

hydrolysis.

3.2 Sugar concentration of syrup

Table 2 shows the result of fructose, glucose, sucrose and total

sugars of the syrup samples.

3.2.1 Fructose concentration

Table 2 showed that significant differences were observed in the

fructose concentration of the syrup formulations. The lowest

fructose concentration was recorded in syrup sample MS2+Y1

(3.49±0.07). However, all the syrup samples prepared from that

the various formulations are poor in fructose concentration (Lee

et al., 2004).

3.2.2 Glucose concentration

Table 2 showed significant variation in the glucose

concentration of the syrup samples (p≤0.05). This was followed

by MR+Y1 with glucose concentration of 8.36%. Glucose

concentration was found lowest in syrup sample from MR+Y2

(7.27%). The result indicates that the syrup samples are poor

glucose syrups but higher in concentration than in fructose

According to Hull (2010), 𝛼-amylase enzyme randomly attacks

gelatinized starch at 1-4 linkages to produce glucose and maltose

but unable to hydrolyze the 1-6 linkages. However, in this study,

the enzyme used was a combination of both 𝛼 & 𝛽-amylase.

However, the result of the glucose concentration of the syrups in

the study were higher than the values recorded by Dziedzic


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(2012) who reported that maple syrups glucose content ranged

from 1.24% to 3.33%.

3.2.3 Sucrose concentration

Sucrose concentration of the syrup sample ranged from 17.24%

to 18.54%. Significant difference was observed in the sucrose

concentration of the syrup samples (p≤0.05). There was no

significant difference between MR+Y1 (17.47%). MS1+Y1

showed the highest sucrose concentration (18.54±0.01%) which

was significantly (p<0.05) higher than the rest of the syrup

samples. This was followed by MS1+Y2 syrup with sucrose

concentration of 18.44%. Sucrose concentration was found

significantly lowest in syrup sample from MS2+Y1 (28.36%).

Dziedzic (2012) reported sucrose content ranging from 61.77 to

70.29% which were greatly higher than that obtained in this

study. This shows that the syrup formulations in this present

study are pure sucrose syrups.

4.0 Conclusion and Recommendation

4.1 Conclusion

Dextrose Equivalent up to 40 was produced with equivalent

sweetness level. The best yam variety was Y1 (Dioscorea

dumenterum) and emzyme source was MS1-malted sorghum

(white Fara Fara). To achieve clear yam sugar syrup that is

viscous, clear and very sweet with high Dextrose Equivalent up

to 40, starch must be extracted from yam first before addition of

enzymes. The enzymes must be extracted from the crude source

before they are added or exogenous enzymes can be used. This

will lead to complete hydrolysis in all from macromolecular to

low molecular weight (sugars)

4.2 Recommendation

Other yam cultivars in the production of syrup should be

investigated on for possible quality improvement. Further

research needs to be done on upgrading the methods of syrup’s

raw material processing and syrup production, improving the

methods, equipments and chemicals used in school laboratory

analysis of syrup quality. More research should also be done on

improving the methods of fortifying and enriching syrup to

improve its nutritional value. Research should be done in

developing appropriate food security and quality management

(FSQM) systems for the various processing methods to meet the

needs and expectation of regulatory bodies and potential

consumers.

4.3 Contribution to Knowledge

Production of syrup without extraction of starch is feasible.

Production of syrup without exogenous enzyme is also feasible.

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Table 1: Physicochemical properties of syrup.

Parameter

Sample

pH

Dextrose

Eqivalent

Density(g/ml) Amylose

Content

Viscosity (cp)

MS 1+ Y 1 5.13±0.08b 36.65±0.01a 1.45±0.01d 5.56±0.01a 980.25±0.09b

MS 2+ Y 1 5.10±0.08c 36.15±0.01c 1.46±0.01cd 4.98±0.01e 980.35±0.09a

MS 1+ Y 2 5.06±0.08d 35.58±0.01d 1.47±0.01bc 5.35±0.01b 960.37±0.09e

MS 2+ Y 2 5.03±0.08e 35.16±0.01e 1.48±0.01ab 4.77±0.00f 965.57±0.09c

MR + Y 1 5.17±0.08a 34.48±0.01f 1.48±0.01ab 5.13±0.01d 960.46±0.09d

http://fenic.technico.ulisboa.pt.resumo/


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MR + Y 2 5.12±0.08bc 36.57±0.01b 1.49±0.01a 5.26±0.01c 960.34±0.09f

LSD 0.025 0.036 0.016 0.032 0.023

*Each value represent mean of duplicate replicates: mean ± standard deviation.

*Mean values having the same superscript along columns are not significantly

different (P<0.05).

Keys:

MS1+Y1 = malted sorghum (white fara-fara) +yam (Dioscorea dumetorum)

MS2+Y1 =malted sorghum (red ksv8) + yam (Dioscorea dumetorum)

MS1+Y2=malted sorghum (white fara-fara) +yam (Dioscorea alata)

MS2+Y2=malted sorghum (red ksv8)) + yam (Dioscorea alata)

MR+Y1= malted rice (faro 60) +yam (Dioscorea dumetorum)

MR+Y2= malted rice (faro 60) + yam (Dioscorea alata)

Table 2: Sugar concentration of syrup.

Parameter

Sample %Fructose %Glucose %Sucrose

MS 1+ Y 1 3.96±0.07b 7.64±0.01c 18.54±0.01a

MS 2+ Y 1 3.49±0.07f 7.47±0.01e 17.24±0.01f

MS 1+ Y 2 3.59±0.07e 8.26±0.01b 18.44±0.01b

MS 2+ Y 2 3.66±0.07d 7.57±0.01d 18.19±0.01d

MR + Y 1 4.26±0.07a 8.36±0.01a 17.47±0.01e

MR + Y 2 3.86±0.07c 7.27±0.01f 18.34±0.01c

LSD 0.024 0.044 0.042

*Each value represent mean of three replicates: mean standard deviation.

*Mean values having the same superscript along columns are not significantly

different (P<0.05).

Keys:

MS1+Y1 = malted sorghum (white fara-fara) +yam (Dioscorea dumetorum)

MS2+Y1 =malted sorghum (red KSV8) + yam (Dioscorea dumetorum)

MS1+Y2= malted sorghum (white fara-fara) +yam (Dioscorea alata)

MS2+Y2= malted sorghum (red KSV8) + yam (Dioscorea alata)

MR+Y1= malted rice (Faro 60) + yam (Dioscorea dumetorum)

MR+Y2= malted rice (Faro 60) + yam (Dioscorea alata)


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Figure 1: Flow diagram for yam flour production

Yam

Washing

Peeling

Slicing

Sun Drying

Milling

Sieving

Packaging

Yam flour


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Washing

Soaking /(48hours)

Sprout/germination (for 5days)

Drying /kilning

Milling

Rice flour

Sieving

Rice grains

Packaging

Packaging

Packaging


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Figure 2: Production of malted rice flour

Sorghum Grain

Washing

Steeping (for 24hours)

Sprouting/germination

Drying

Milling

Sorghum

Sieving

Packaging


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Figure 3: Production of malted sorghum flour

pH adjustment

Figure 4: production of sugar syrup

Starch

Slurry

pH adjustment

Boilng at 700C

Cooling

Filtration/packaging Sugar syrup

Sugar syrup

physico-chemical properties of sugar syrup produced …

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