Scholarly article on topic 'Physico-chemical properties of wheat-yam flour composite bread'

Physico-chemical properties of wheat-yam flour composite bread Academic research paper on "Agriculture, forestry, and fisheries"

CC BY-NC-ND
0
0
Share paper
Academic journal
Nigerian Food Journal
OECD Field of science
Keywords
{Physico-chemical / Wheat / Yam / Composite / Bread}

Abstract of research paper on Agriculture, forestry, and fisheries, author of scientific article — C. Amandikwa, M.O. Iwe, A. Uzomah, A.I. Olawuni

Abstract This work investigated the effect of yam flour substitution on characteristics of wheat bread and also determined the functional properties of the experimental flour samples. Flours were obtained from three varieties of yam (Dioscorea rotundata, Dioscorea alata and Dioscorea bulbifera) and blended with wheat flour at 25, 50 and 75 percent levels of substitution for bread production. Wheat flour (WF) and each of the yam flours were used as the positive and negative controls respectively. The functional properties (bulk density, water/oil absorption capacities, emulsion activity) of the flour samples were determined while the proximate, physical and sensory characteristics of loaves were also determined. The functional properties of the flour samples ranged from 0.42g/ml to 0.67g/ml packed bulk density; 0.39g/ml to 0.47g/ml loose bulk density; 0.88ml/g to 2.10ml/g oil absorption capacity; 1.50ml/g to 3.90ml/g water absorption capacity and 43.75% to 49.37% emulsion activity. The proximate composition of the bread samples ranged from 26.82% to 38.90% moisture, 4.23% to 5.10% fat, 6.10% to 9.25% protein, 1.90% to 2.45% ash, 0.12% to 0.64% crude fiber and 46.43% to 56.71% carbohydrate. The volume, weight and specific volume of loaves varied from 200ml to 400ml, 142.6g to 170.2g and 1.18ml/g to 2.81ml/g respectively. The crack formation of bread samples showed that there were no cracks on wheat bread (WF) and 25% yam flour substituted breads while 100 percent yam flour breads had large cracks. The sensory properties of the 25% yam flour substituted breads were statistically (p>0.05) the same with the 100% wheat bread but differed from all the other bread samples. The mean score of the sensory attributes decreased as yam flour increased in the formulation. Sensory Evaluation of the bread samples showed that substitution level of 25% yam flour produced bread that was acceptable to the consumers whereas up to 50% and above were not acceptable. It is therefore recommended that substitution level of not more than 25% yam flour be used for yam/wheat composite bread production.

Academic research paper on topic "Physico-chemical properties of wheat-yam flour composite bread"

ELSEVIER

Available online at www.sciencedirect.com

ScienceDirect

Nigerian Food Journal ■ (■■■■) III III

www.elsevier.com/locate/nifoj

Physico-chemical properties of wheat-yam flour composite bread

C. Amandikwaa,n, M.O. Iweb, A. Uzomaha, A.I. Olawunia

aDepartment of Food Science and Technology, Federal University of Technology, PMB 1526 Owerri, Imo State, Nigeria bDepartment of Food Science and Technology, Michael Okpara University of Agriculture Umudike, PMB 7267 Umuahia, Abia State, Nigeria

Abstract

This work investigated the effect of yam flour substitution on characteristics of wheat bread and also determined the functional properties of the experimental flour samples. Flours were obtained from three varieties of yam (Dioscorea rotundata, Dioscorea alata and Dioscorea bulbifera) and blended with wheat flour at 25, 50 and 75 percent levels of substitution for bread production. Wheat flour (WF) and each of the yam flours were used as the positive and negative controls respectively. The functional properties (bulk density, water/oil absorption capacities, emulsion activity) of the flour samples were determined while the proximate, physical and sensory characteristics of loaves were also determined. The functional properties of the flour samples ranged from 0.42 g/ml to 0.67 g/ml packed bulk density; 0.39 g/ml to 0.47 g/ml loose bulk density; 0.88 ml/g to 2.10 ml/g oil absorption capacity; 1.50 ml/g to 3.90 ml/g water absorption capacity and 43.75% to 49.37% emulsion activity. The proximate composition of the bread samples ranged from 26.82% to 38.90% moisture, 4.23% to 5.10% fat, 6.10% to 9.25% protein, 1.90% to 2.45% ash, 0.12% to 0.64% crude fiber and 46.43% to 56.71% carbohydrate. The volume, weight and specific volume of loaves varied from 200 ml to 400 ml, 142.6 g to 170.2 g and 1.18 ml/g to 2.81 ml/g respectively. The crack formation of bread samples showed that there were no cracks on wheat bread (WF) and 25% yam flour substituted breads while 100 percent yam flour breads had large cracks. The sensory properties of the 25% yam flour substituted breads were statistically (p > 0.05) the same with the 100% wheat bread but differed from all the other bread samples. The mean score of the sensory attributes decreased as yam flour increased in the formulation. Sensory Evaluation of the bread samples showed that substitution level of 25% yam flour produced bread that was acceptable to the consumers whereas up to 50% and above were not acceptable. It is therefore recommended that substitution level of not more than 25% yam flour be used for yam/wheat composite bread production.

© 2015 The Authors. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Keywords: Physico-chemical; Wheat; Yam; Composite; Bread

1. Introduction

Yam belongs to the order Lilliales, family Dioscoreacea and genus Dioscorea. Yam comprises of many varieties which are edible and some others which are not edible (Eke, 1990). Yam is a staple food for millions of people in the world, providing an important source of carbohydrate and more protein on dry weight basis than is commonly assumed (IITA, 1992). Yam may be boiled, baked, fried, roasted and mashed to suit regional tastes and customs of the people. Bread generally represents a food

*Corresponding author. E-mail address: amandikwa125@yahoo.com (C. Amandikwa). Peer review under responsibility of Association of Vice-Chancellors of Nigerian Universities.

prepared from dough and baked to produce an outer crust and an inner cell structure (Barret, 1975). Bread is described as a loaf made from wheat or rye flour.

Previous studies have shown the incorporation of non - wheat flours in bread production. Cardenas et al. (1993) replaced 30% of wheat flour with sweet potato flour in bread and there was no difference in sensory characteristics or protein quality of the sweet potato-wheat bread.

Furthermore, Greene and Bovel-Benjamin (2004) investigated the microscopic and sensory properties of bread supplemented with sweet potato and found that substitution level of 65% can be used in bread making. Similarly, Ukpabia and Uchechukwu (2001) investigated the potentials of Chinese yam (Discorea esculenta) flour in bread making and found that at 30% level of substitution, the yam/wheat bread showed no significant difference from

http://dx.doi.org/10.1016/j.nifoj.2015.04.0n

0189-7241/© 2015 The Authors. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

the whole wheat bread. In some other studies with cereal grains, Edema et al. (2005) evaluated the production of sour maize bread using soybean flour blends. These workers suggested the addition of not more than 10% protein supplement in the form of soybean flour or other legumes (with amino acid profile comparable to that of soybean) that is expected to give nutritionally balanced and acceptable maize-bread.

Product diversification with yam tubers has been minimal and some of these yam varieties are not widely cultivated due to inadequate utilization. There is, therefore, the need to investigate the bread making potentials of some of these yam varieties. Successful production of bread supplemented with yam flour will not only encourage improved cultivation of this crop but will also enhance the economic value of the crop. Therefore the specific objective of the present research was to evaluate the effect of three yam varieties on the characteristic properties of bread.

2. Materials and methods

2.1. Study location

The study locations were at the Department of Food Science and Technology, Michael Okpara University of Agriculture Umudike, Abia State and the Department of Food Science and Technology, Federal University of Technology Owerri, Imo State, both in Nigeria. These locations are predominantly occupied by Ibo speaking ethnic groups in Nigeria who cultivate and consume a large proportion of annual yam production in Nigeria.

2.2. Materials

The different yam varieties namely Dioscorea rotundata (white yam), Dioscorea alata (water yam) and Dioscorea bulbifera (aerial yam) were purchased from the farmers in the respective locations in Abia State of Nigeria. Wheat flour (Golden Penny brand) and other ingredients for bread were purchased from the local market.

2.2.1. Preparation of yam flour samples

Five kilogram each of the yam varieties were peeled, thinly sliced, washed and blanched in boiling water for 4 min and then sun dried until the moisture content was between 10% and 13%. The dried chips were milled to pass through 250 mm mesh sieve to obtain the flour. Each flour sample Dioscorea rotundata flour (DRF), Dioscorea alata flour (DAF) and Dioscorea bulbifera flour (DBF) was stored separately in tightly covered plastic jars to prevent moisture re-absorption.

2.3. Research design

The research was laid out in a completely randomized design comprising of two factors. Factor A is yam variety, while factor B is level of substitution; 25%, 50% and 75% level of substitution. Hundred percent wheat flour (WF) bread was used as the positive control while 100% yam flour bread was used as the negative control. The individual flour samples were subjected to functional properties while the bread samples were subjected

to proximate composition analysis, physical characteristics and sensory evaluation. Proximate and functional analyses were done in triplicate. Statistical differences of data obtained were determined by ANOVA (p> 0.05) using SPSS (12 Software for windows) while the significant means were compared using Fisher's Least Significant Difference (LSD) procedure (Roessler, 1984).

2.4. Determination of functional properties

2.4.1. Bulk density (BD)

Bulk density of the flour samples was determined by the gravimetric method described by Okezie and Bello (1988). A weighed sample (10 g) was put in a calibrated 25 ml measuring cylinder and the volume was recorded as the loose volume. The bottom of the cylinder was tapped repeatedly on a firm pad on a laboratory bench until a constant volume was observed. The packed volume was recorded. The loose bulk density (LBD) and packed bulk densities (PBD) were calculated as the ratio of the sample weight to the volume occupied by the sample before and after tapping.

2.4.2. Water/oil absorption capacity

Water and Oil absorption capacities (WAC/OAC) for each flour sample were determined by the method of Abbey and Ibeh (1988). The sample (10% w/v) was weighed into a clean conical flask and was mixed thoroughly with distilled water/oil using a warring mixer for 30 s. The sample was then allowed to stand for 30 min at room temperature, after which it was centrifuged at 5000 rpm for 30 min. The free water or oil (supernatant) was read directly from the graduated centrifuge tube. The absorbed water/oil was converted to weight (in grams) by multiplying by the respective density (water, 1 g/ml and soybean oil, 0.924 g/ml). The water and oil absorption capacities were express in grams of water/oil absorbed per gram of flour sample.

2.4.3. Emulsion activity (EA)

Emulsion activity was determined according to the modified method of Okezie and Bello (1988). Two grams of flour sample was blended with 25 ml distilled water at room temperature for 30 s in a warring blender at 1600 rpm. After complete dispersion, 25 ml soy oil was added gradually and blended for another 30 s. The blend was centrifuged for 5 min at 1600 rpm. The volume of oil which separated from the sample after centrifugation was read directly from the tube. Emulsion activity was calculated as the ratio of height of emulsion to the total height expressed as a percentage.

2.5. Bread making process

The bread was produced according to the method described by Edema et al. (2005). The flours obtained were blended with wheat flour (WF) at 25:75, 50:50 and 75:25 levels of substitution for bread production. Yam: WF at 100:0and 0:100 levels were used as control. The bread recipe consisted of 100 g of each blend, 6.2 g sugar, 1.7 g salt, 3.9 g margarine, 3.3 g yeast, 0.02 g ascorbic acid and 56 ml of warm water (43 °C). More water was

added to the yam flour based products to reach 500 BU of consistency. The dry ingredients were thoroughly mixed and the fat was then rubbed in. The ascorbic acid was dissolved in some of the warm water and added to the flour. The yeast was then dissolved in some of the water and added to the flour. The mixture was kneaded into smooth pliable elastic-like dough, covered and allowed to ferment (30 min). It was then knocked back and cut into size and transferred to a lightly greased pan and allowed to proof (15 min), baked at 200 °C for 20 min. The baked product was cooled and packaged in polythene bags.

2.6. Determination of proximate composition

The chemical composition was determined using the method of AOAC (1990). The crude fiber content was determined on 5 g sample by dilute acid and alkali hydrolysis. The carbohydrate content was calculated by difference as the nitrogen free extractive (NFE).

2.7. Determination of physical properties of bread samples

Each loaf was weighed and the volume determined using the AACC (1983) method in which the pinto bean displacement was modified by using soybean. The displaced soybean was used to express the volume of the loaf. Specific loaf volume (SLV) was calculated as the ratio of loaf volume to the weight. Crack formation was determined visually.

2.8. Sensory evaluation

Twenty panelists made up of bread consumers (10 males and 10 females) were used. Attributes tested on a 9 point hedonic scale (Iwe, 2002) included flavor, taste, appearance, texture and general acceptability where 1 = disliked extremely and 9 = liked extremely.

3. Results and discussion

3.1. Functional properties of flour samples

The functional properties of flour samples are shown in Table 1. These define the consumers' requirements and determine the suitability of the foodstuff for a given purpose. The

Table 1

Functional properties of flour samples.

Flour LBD (g/ml) PBD (g/ml) OAC (ml/g) WAC (ml/g) EA (%)

DRF 0.46a 0.48b 1.66b 3.10c 45.24c

DAF 0.40b 0.42c 2.10a 3.60b 49.37a

DBF 0.39b 0.53b 1.66b 3.90a 43.75d

WF 0.47a 0.67a 0.88c 1.50d 47.06b

Means with the same superscript within the same column are not significantly different (p > 0.05). DRF, Dioscorea rotundata flour; DAF, Dioscorea alata flour; DBF, Dioscorea bulbifera flour; WF, Wheat flour; PBD, Packed bulk density; LBD, Loose bulk density; OAC/WAC, Oil/Water absorption capacity; EA, Emulsion activity.

loose bulk density of the flour samples varied from 0.39 g/ml to 0.47 g/ml with wheat flour, 0.47 > D. rotundata flour, 0.46 > D. alata flour,0.40 > D. bulbifera flour,0.39. The packed bulk density ranged between 0.42 g/ml and 0.67 g/ml with WF,0.67 > DBF,0.53 > DRF,0.48 > DAF,0.42. The difference observed in bulk density values is found to be significantly different (p > 0.05). The WAC and OAC of the flour samples are shown in Table 1. The OAC ranged from 0.88 ml/g (WF) to 2.1 ml/g (DAF). Similarly WAC was lowest in WF (1.5 ml/g), while DBF recorded the highest value (3.9 ml/g). The statistical analysis showed that these differences were significant at p > 0.05. DBF gave the lowest emulsion activity (EA) (43.75%), while the highest value was recorded for DAF (49.37%) and this was significantly different from that obtained for WF (47.06%) (Table 1). This result suggests that DAF may serve as a better emulsifier than all the other flour samples.

The packed bulk density of 0.53 g/ml for DBF is the same with that reported by Igyor et al. (2004) while the loose bulk density of 0.39 g/ml differed from 0.60 g/ml reported by the same author. Also Igyor et al. (2004) reported a packed bulk density of 0.62 g/ml for D. rotundata flour whereas this present result gave 0.48 g/ml and LBD of 0.46 g/ml contrary to 0.74 g/ml reported by Igyor et al. (2004). The observed variations in the results could be attributed to the differences of the species, and other environmental factors under which the yams were grown. Moorthy and Ramanujam (1986) and Asaoka et al. (1991) reported that age, variety, growth season and cultivar's type of root tubers affect their physico-chemical properties. Maturity at harvest, the length of storage and the elapsed time between harvesting and processing period may also contribute to these variations (Ihekoronye and Ngoddy, 1985). Bulk density gives an indication of the relative volume of packaging material required .Generally, higher bulk density is desirable for greater ease of dispersibility and reduction of paste thickness (Udensi and Eke, 2000). Low bulk densities of flour are good physical attributes when determining transportation and storability since the products could be easily transported and distributed to required locations (Agunbiade and Sanni, 2001). The result of this present research showed that wheat flour has higher bulk density than yam flour and should be used where such properties are required. Considering the yam varieties, DRF, 0.46 and DBF, 0.53 had the highest loose and packed bulk densities respectively and should be recommended where such attributes are of great importance. Previous reports (Igyor et al., 2004) on water absorption capacity showed that the WAC for D. bulbifera flour and D. rotundata flour were 3.5 ml/g and 6.0 ml/g respectively. Ukpabia and Uchechukwu (2001) gave the oil absorption capacity and WAC of D. esculenta flour as 1.9 ml/g and 1.8 ml/g respectively. These variations have been attributed to the growth season and age of the tubers amongst other things (Asaoka et al., 1991; Moorthy and Ramanujam, 1986). The oil absorption of 1.9 ml/g is higher than 1.66 ml/g recorded for DRF and DBF in this present study. Niba et al. (2001) stated that WAC is important in bulking and consistency of product as well as baking applications. Oil gives soft texture and good flavor to food. Therefore absorption of oil by food products improves mouth feel and flavor retention. A high

OAC is valuable in ground meat formulations, meat replacers and extenders, doughnuts, pancakes and soups (Onimawo and Egbekun, 1998). This implies that DAF which had the highest OAC (2.10 ml/g) could serve as a useful raw material for such food products. The highest value of 49.37% (emulsion activity) recorded for DAF suggests that it may serve as a better emu-lsifier than all the other flour samples.

3.2. Proximate composition of bread sample

The moisture content ranged from 26.82 to 38.90%; protein, 6.10% to 9.25%; ash,1.90% to 2.45%; crude fiber, 0.12% to 0.64% and carbohydrate (by difference) 46.43% to 56.71% (Table 2). There was a significant (p > 0.05) difference in the proximate composition of the bread samples. The moisture content increased as yam flour increased in the formulation whereas the fat, protein and carbohydrate decreased as yam flour increased in the formulation.

There appeared to be greater retention of moisture by the bread sample as the yam flour levels increased. Moisture content of the bread samples increased significantly as yam flour increased in the formulation. Similar result was reported by Adebowale et al. (2009) on sweet potato-wheat bread. On the contrary, the increased yam flour level lead to a decrease in the fat, protein and carbohydrate composition of the bread samples and a corresponding increase in the crude fiber level. The fat (5.1%) and ash (2.1 %) content recorded in this present research for wheat bread is similar to that reported by Dhingra and Jood (2002) for WF bread (5.4%, fat; 2.0%, ash). The carbohydrate levels may

Table 2

Proximate composition of bread sample (%).

Flour blends Moisture Fat Protein Ash Crude fiber carbohydrate

WF 26.82g 5.100a 9.250a 2.000cd 0.1200g 56.71a

75 28.36f 4.920ab 8.050cd 2.100c 0.1200g 56.45b

WF:25DRF

50 30.74e 4.540de 6.650h 2.150c 0.1300fg 55.79c

WF:50DRF

25 32.40d 4.450def 6.650h 2.200b 0.1400d 54.16d

WF:75DRF

DRF 34.16d 4.400fg 6.100' 2.400ab 0.1800d 54.00d

75 26.96fg 4.750bc 8.700ab 1.980cd 0.1200g 56.62a

WF:25DAF

50 35.42bc 4.630cd 8.400b 1.950cd 0.1300fg 49.47e

WF:50DAF

25 WF: 36.82b 4.460def 7.700e 1.930d 0.1500ef 48.04ef

DAF 38.90a 4.420efg 7.000g 1.900d 0.1500ef 47.63f

75 33.52d 4.820bc 8.400b 2.300b 0.1500ef 50.82e

WF:25DBF

50 WF: 35.06c 4.470def 8.230b 2.300b 0.3200c 49.62e

25 38.32a 4.410efg 7.950d 2.350ab 0.3800b 46.59f

WF:75DBF

DBF 38.90a 4.230g 7.350f 2.450ab 0.6400a 46.43f

Means bearing the same superscript within the same column are not significantly different (p > 0.05).DRF, Dioscorea rotundata flour; DAF, Dioscorea alata flour; DBF, Dioscorea bulbifera flour; WF, Wheat flour.

vary according to maturity at harvest, varietal differences and age of storage (Moorthy and Ramanujam, 1986; Ihekoronye and Ngoddy, 1985). In this study, products from DBF had the highest crude fiber. This implies that D. bulbifera flour could serve as a useful supplement in food material where fiber is of great importance.

3.3. Physical properties of bread samples

The volume, weight and specific volume (Table 3) of the loaves ranged from 200 to 400 ml, 142.6 to 170.2 g and 1.18 to 2.8 ml/g respectively. The loaf volume decreased proportionately with increase in yam flour in the formulation. The result showed that at 50% WF substitution, small cracks were observed on the yam-wheat breads while 100% yam breads had the largest cracks (Table 3).

Considering the yam varieties, the DBF based products had the lowest SLV (1.18 ml/g) (Table 3).

The low oven spring recorded by the composite bread samples is attributed to low gluten content which has a direct contribution to the viscoelastic properties of WF dough (Okaka, 2005). The weight of the loaves increased with increase in yam flour. This may be as a result of higher water absorption observed in the yam based bread samples during the dough mixing process. Also there was a significant difference (p > 0.05) in the specific loaf volume of the loaves. The SLV decreased with increase in yam flour in the formulation. This corroborates the reports of Ukpabia and Uchechukwu (2001) on Chinese yam (D. esculenta) flour at 30% level of yam flour substitution for composite bread production. However the SLV of 2.02 ml/g to 4.98 ml/g obtained from the research by Ukpabia and Uchechukwu (2001) is comparably higher than that obtained from this present study. This implies that Chinese yam have good baking characteristics in terms of loaf volume. The cracks observed on 50% substituted breads was contrary to that reported by Ukpabia and Uchechukwu (2001) who reported no crack even on 100% Chinese yam bread.

Table 3

Physical properties of wheat/yam bread loaves.

Flour blends Volume (ml) Weight (g) SLV (m/g) Crack formation

WF 400.0a 142.60" 2.810a No crack

75 WF:25DRF 340.0c 142.90s 2.380b No crack

50 WF:50DRF 250.0d 145.40k 1.710d Small cracks

25 WF:75DRF 228.0fg 146.90s 1.550c Small cracks

DRF 223.0gh 153.10g 1.460gh Large cracks

75 WF:25DAF 355.0b 147.70i 2.400h No crack

50 WF:50DAF 250.0d 148.50h 1.680d Small cracks

25 WF:75DAF 240.0def 155.90f 1.540ef Small cracks

DAF 232.0efg 162.60d 1.430h Large cracks

75 WF:25DBF 340.0c 155.30f 2.190c No crack

50 WF:50DBF 244.0dc 163.50c 1.490fg Small cracks

25 WF:75DBF 210.0hi 167.60b 1.250i Small cracks

DBF 200.0i 170.20a 1.180s Large cracks

Means bearing the same superscript within the same column are not significantly different (p > 0.05). DRF, Dioscorea rotundata flour; DAF, Dioscorea alata flour; DBF, Dioscorea bulbifera flour; WF, Wheat flour; SLV, Specific loaf volume.

Table 4

Organoleptic characteristics of wheat/yam breads.

Bread sample Flavor Taste Texture Appearance General acceptability

WF 6.800a 6.750a 6.950a 7.000a 7.200a

75 WF:25DRF 6.650a 6.350a 7.200a 6.600a 7.250a

50 WF:50DRF 4.950bc 4.950bc 4.250b 4.150c 4.200b

25 WF:75DRF 4.350c 4.050cd 3.350c 3.550cd 3.300c

DRF 3.850c 4.500cd 3.300cd 3.050d 3.400c

75 WF:25DAF 6.700a 6.750a 7.200a 5.950b 7.050a

50 WF:50DAF 5.000b 4.950bc 4.250b 4.400c 4.800b

25 WF:75DAF 3.850c 4.500cd 3.350c 2.400e 2.850c

DAF 4.000c 2.850f 3.350c 1.950f 2.400d

75 WF:25 DBF 5.700b 5.850ab 6.650a 5.150bc 7.250a

50 WF:50 DBF 3.800cd 3.850de 4.550b 3.650cd 2.850c

25 WF:75 DBF 3.200d 3.650def 2.450d 2.500e 2.650cd

DBF 2.550e 2.950ef 2.150d 2.400e 2.650cd

Means bearing the same superscript within the same column are not significantly different (p > 0.05).

DRF, Dioscorea rotundata flour; DAF, Dioscorea alata flour; DBF, Dioscorea bulbifera flour; WF, Wheat flour.

3.4. Sensory characteristics of bread samples

The flavor, texture, appearance, taste and general acceptability of the 25% yam flour substituted breads were statistically the same with the 100% wheat bread but differed from all the other bread samples (Table 4). The mean score of the sensory attributes decreases as yam flour increases in the formulation. The result showed that up to 25% level of substitution of wheat with yam flour was acceptable for bread making while 50% yam substituted bread were not acceptable.

The mean scores of the sensory attributes of 25% yam flour substituted breads were statistically the same with 100% WF bread. The result obtained from this present study is in good agreement with that reported by IITA (1995) that successfully substituted flour made from 297 genotype of DAF (D. alata) to obtain good quality bread at 40% WF substitution. 50% yam flour substituted breads were generally unacceptable to the panelists except 50% DAF which was acceptable in terms of flavor. The mean score of the bread samples decreased as yam flour increased in the formulation. Also Ukpabia and Uchechukwu (2001) reported on the production of acceptable bread from chinese yam (D. esculenta) flour at 30% WF substitution. One hundred percent yam bread gave the worst product that was unacceptable to the consumers. The result of this research shows that yam flour could be used in composite bread production at 25% level of substitution and beyond this level bread characteristics may be affected. Similarly, results of this study showed that as the amount of yam flour increased to 50%, bread was less acceptable.

4. Conclusion

The result of the functional properties showed that the emulsion activities of the yam flours compared well with that of the wheat flour. Also the water absorption capacity of each of the yam flour was about 50% higher than that of the wheat

flour. Thus suggesting that these yam varieties may be useful in food formulations where these characteristics are of great importance. Acceptable bread comparable to wheat bread can be produced at 25% level of yam flour substitution. This study therefore recommends extensive cultivation and utilization of these yam varieties since they could serve as useful supplements for composite bread production. Meanwhile, consumption of these products should be accompanied with protein rich diets such as legumes or milk in order to eat a nutritionally balanced diet.

References

AACC, 1983 (with revisions 1983-1990). Approved Methods of the AACC, 8th ed. American Association of Cereal Chemist, St Paul, MN (Method 4613).

Abbey, B.W., Ibeh, G.O., 1988. Functional properties of raw and heat processed cowpea flour. J. Food Sci. 53 (6), 1774-1777.

Adebowale, O.J., Idowu, M.A., Bankole, M.O., 2009. Influence of sweet potato flour diastatic activity on rheological, baking and sensory characteristics of wheat-sweet potato composite bread. Niger. Food J. 27, 204-209.

Agunbiade, S.O., Sanni, M.O., 2001. The effect of ambient storage of cassava tubers on starch quality. In: Root Crops. The small processor and development of Local Food Industries for market economy. Proceedings of the Eight Triennial Symposium of the International Society for Tropical Root Crops. African Branch(ISTRC-AB). 12-16 Nov 2001. IITA Ibadan, Nigeria. pp. 189-194.

Association of Official Analytical Chemists (AOAC), 1990. Official Methods of Analysis, 15th ed. Washington, DC, USA.

Asaoka, M., Blanchard, J.M.V., Richard, J.E., 1991. Seasonal effects on the physiochemical properties of starch from four cultivars of cassava. Starch/ Starke 43, 455-459.

Barret, F.F., 1975. The role of bread in international nutrition. Cereal Food World 1975.

Cardenas, H., Kalinowski, J., Huaman, Z., Scott, G., 1993. Nutritional evaluation of sweet potato cultivars (Ipomea batata. L) used as a partial substitute for wheat flour. Arch. Lat. Nutr. 43, 304-309.

Dhingra, S., Jood, S., 2002. Organoleptic and nutritional evaluation of wheat breads supplemented with soybean and barley flour. Food Chem. 77, 479-488.

Edema, M.O., Sanni, L.O., Sanni, A.I., 2005. Evaluation of maize-soy-bean flour blends for sour dough maize bread production in Nigeria. Afr. J. Biotechnol. 4 (9), 911-918.

Eke, G.B., 1990. Successful Yam Growing. Trio pub, Owerri4-5.

Greene, J.L., Bovel-Benjamin, A.G., 2004. Macroscopic and sensory evaluation of bread supplemented with sweet potato flour. J. Food Sci., 69; 167-173.

Igyor, M.A., Ikyo, S.M., Gernah, D.I., 2004. The food potentials of potato yam. (Dioscorea bulbifera). Nig. Food J. 22, 312.

Ihekoronye, A.I., Ngoddy, P.O., 1985. Integrated Food Science and Technology for the Tropics. Macmillan Pub, London.

IITA, International Institute for Tropical Agriculture, 1992. Biotechnology Research at IITA. An Introductory Booklet. IITA Ibadan, Nigeria.

IITA, International Institute for Tropical Agriculture, 1995. Yam Research at IITA: 1971-1993. IITA, Ibadan4-7.

Iwe, M.O., 2002. Handbook of Sensory Methods and Analysis. Rejoint Communication Service Ltd., Enugu7-12.

Moorthy, S.N., Ramanujam, T., 1986. Variations in properties of starch in cassava varieties in relation to age of the crop. Starch/Starke 38 (2), 58-61.

Niba, L.L., Bokanga, M., Jackson, F.I., Schlimme, D.S., Li, B.W., 2001. Physico-chemical properties and starch granular characteristics of flour from various Manihot esculenta (cassava) genotypes. J. Edn. Sci. 67, 1701.

Okaka, J.C., 2005. Bread making ingredients and technology In:. Handling, Storage and Processing of plant foods. OCJ Publishers, Enugu45-78.

Okezie, B.O., Bello, A.B., 1988. Physiochemical and functional properties of winged bean flour and isolate compared with soy isolate. J. Food Sci. 53 (11), 450-454.

Onimawo, A.I., Egbekun, K.M., 1998. Comprehensive Food Science and Nutrition Revised edn. Grace foundation pub, Jos.

Roessler, E.E., 1984. Statistical evaluation of experimental data; multiple comparison. In: Gruenwedel, D.W., Whitaker, J.R., Marcel, D. (Eds.), Food Analysis, Principle and Techniques, pp. 12-13.

Udensi, A., Eke, O., 2000. Proximate composition and functional properties of flour produced from Mucuna cochinensis and Mucuna utles. In: Proceedings of the 1st Annual Conference of the College of Agriculture and Veterinary Medicine, Abia State University. 10-13th Sept. pp. 170-174.

Ukpabia, U.J., Uchechukwu, N., 2001. Potentials of chinese yam (Dioscorea esculenta) flour in bread. In: Proceedings of the Eight Triennial Symposium of the International Society for Tropical Root Crops, African Branch (ISTRC-AB)12- 16th Nov. Ibadan Nigeria. pp. 219-221.