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Wheat Cowpea Composite Flour Baking Biology Essay

ABSTRACT

The fortified of soft wheat flour with Cowpea flour in bread making was investigated. The Soft wheat flour (SWF) was substituted by Cowpea four at levels of 5, 10, 15 and 20%. The protein content of composite breads ranged from 6.1 - 9.9%. No significant difference was observed in the nutrient

contents of control (wheat bread) and composite bread at 5% addition of Cowpea. Water and oil absorption capacities of composite flours increased with increasing levels of Cowpea flour in the blend. The specific loaf volume decreased significantly with increased Cowpea content of blends.

Sensory panel rating (80.3%) of the 10% Cowpea flour content of composite bread was not significantly different from the score (83.5%) of the 5% level of SWF substitution but was significantly different from a score of 88.3% for the control (Soft Wheat-bread) .

Key words:

Plantain, composite, dough bread and biscuit.

MATERIALS AND METHODS

Materials

Six kilo grammas (6kg) of Cowpea was kindly provided from Sebha University, Libya. The Soft wheat flour used was obtained from Azda Supermarket in Edinburgh City.

Bread making

Flour samples containing wheat and cowpea flours were formulated at 0, 5, 15 and 20% (w/w) level of cowpea flour substitutions for bread making

Proximate Composition

Proximate analyses of the samples were carried out using official AOAC methods [8] for moisture (14.004), crude fat (14.081), crude fiber (7.0006), ash (14.006) and crude protein (47.021). A nitrogen to protein conversion factor of 6.25 was used. Carbohydrate was calculated by difference.

Functional Properties

Water and oil absorption capacity:

Water and oil absorption properties of the composite flour were determined following methods of Sathe et al. [9]. Briefly, flour sample (2 g) was mixed with 20 ml distilled water for water absorption and 20 ml of oil for oil absorption in a Kitchen blender (Model dePC 3, France) at high speed for 30 (s). Samples were then allowed to stand at 30°C for 30 min then centrifriged at 10,000rpm for 30 min.

The volume of supernatant in a graduated cylinder was noted. Density of water was taken to be 1g/ml and that of oil was determined to be 0.93 g/ml. Means of triplicate determinations were reported. Foaming capacity and stability were studied according to the methods described by

Desphande et al. [10]. For stability, the flour sample (0.5g) was blended for 30 min in distilled water (40 ml) at top seed in a Moulinex blender. The whipped mixture was transferred into a 100 ml graduated cylinder. The blender was rinsed with 10 ml distilled water which was then gently added to the graduated cylinder. Foam volume in the cylinder were recorded per sample after 30 min standing. Triplicate measurements were made for each sample and mean values recorded.

Preparation of Bread

AACC method 10-lOB (1983) was used to bake bread, doughs were prepared from wheat flour with and with out the addition of different additives of cowpea flour. The ingredients were mixed for five minutes by Breville SHM2 Food Mixer. The dough was baked at 200°C for 20 min., in a pan loaf in Russell Hobbs 14552 Mini Oven.

Evaluation of Bread Characteristics

Bread characteristics or baking qualities were evaluated by measuring the loaf volume, specific loaf volume and the organoleptic characteristics.

The rapeseed displacement method as described by Giami et al. (Giami et al, 2004) was used to determine the loaf volume of the bread. Briefly, loaf volume was measured by seed displacement using Sesame in place of rapeseed. A 2 L measuring cup box was filled with Sesame seeds and the surface leveled with a ruler. The loaf whose volume was to be determined was weighed and the loaf placed in the 2 L cup. The Sesame from the measuring cylinder was poured over the loaf in the box and leveled. The volume of the spilled Sesame was noted as the volume of the loaf. The specific loaf volume (SLV) of the loaf was calculated as the loaf volume per weight of the loaf (cm3/g).

Specific volume of loaf = V/wt (cm3/g)

All determination was in three replicate.

Sensory evaluation was performed 24 hours after baking to evaluate loaf appearance, crust colour, crumb colour, taste/flavour and overall acceptability of the bread sample.

The bread samples were sliced into pieces of uniform thickness and served with water. Twenty panel members (familiar with quality attributes of local bread) were randomly selected from students and staff of the Department of Food Science and Technology, to perform the evaluation. Panelists evaluated bread samples on a 9 point hedonic scale quality analysis [17] with 9 = liked extremely, 8 = liked very much, 7 = liked, 6 = liked mildly, 5 = neither liked nor disliked, 4 = disliked mildly, 3 = disliked, 2 = disliked very much and 1 = disliked extremely .

Statistical Analysis

Analysis for significant differences in the results obtained were performed by using the F-test and the least significant Difference Test (LSD) [19].

RESULTS

Blanching of plantain slices in hot 1.25% NaHSO3 solution resulted in bleaching of plantain slices with reduced browning of dehydrated products and stability of packaged flour.

The proximate contents of plantain flour, wheat flour and wheat-plantain composite bread are presented in Table 2. The protein contents of wheat and plantain flours were 12.86% and 2.30% respectively. Differences in the nutrient contents of 0 (wheat bread), the control, and 5% level of wheat flour substitution by plantain flour were not significant (P>0.05). The protein contents of the composite breads ranged from 5.6 - 10.2%. Protein contents decreased significantly while carbohydrate contents increased with increasing levels of plantain flour in the composite flours. The crude fibre and ash contents of composite breads differ significantly p≤0.05 at higher levels of dilution of wheat with plantain.

The functional properties of wheat plantain composite flours are presented in Table 3. Both water and oil absorption increased with increasing contents of plantain flour in

the blends. Differences in water absorption capacities of flours increased significantly from the 90:10 to 100:0 (w/w)% wheat to plantain flour. Differences in the values for oil absorption from the 100:0 to 50:50 (w/w)% wheat: plantain flour blends were not significant (P>0.05). Similarly, differences in the values for bulk density and emulsion activity were not significant (P>0.05). However, the emulsion activity and stability decreased with increased content of plantain in flour blends. Foam capacity increased from the 100:0 to 80:20 (w/w)% wheat:plantain flour blend. Differences in the values obtained for foam stability were not significant. However, the foam volume on whole plantain flour sample was insignificant and stable.

Data on the baking characteristics of wheat and plantain composite bread are given in Table 5. The oven spring and specific volume of plantain composite breads decreased significantly with increasing plantain flour content of the composite flour. Beyond 5% level of wheat flour substitution the oven spring and specific loaf volume were significantly less than the value for control. Further increase up to 30% level of wheat flour substitution produced a poorer loaf.

Presented in Table 6 are the sensory attributes of wheat-plantain composite bread. Taste panel ratings of sensory properties of the bread samples increased significantly (P≤0.05) with increased contents of wheat flour in the composite. For mixtures up to 30% of plantain flour, the scores for loaf appearance, crust colour, crumb colour, taste/flavour and overall acceptability were significantly (P≤0.05) lower than the 20, 10, and 5% mixtures. Differences in panel scores for the control bread and the 5% dilution were nonsignificant.

Scores obtained at 30% level of substitution were less acceptable. At 10% level of substitution of plantain flour for wheat flour, acceptable loaves of bread were obtained. However, bread produced with 10% plantain flour in the mixture had total score of 80.2% which was not significantly different from the 5% level of substitution with a total score of 83.8%. However, the control had a total score of 88.4% and significantly different from bread with 10% plantain flour in the mixtures. These scores which represent cumulative sensory panel scores for the breads represent fractions of the total score (100%) for the tested attributes and demonstrate high level of acceptability of the breads up to 10% level of substitution of wheat flour by plantain flour.

CONCLUSION

The protein content of wheat/plantain composite breads ranged from 5.6 - 10.2%. Water and oil absorption capacities of the flour blends increased with increasing plantain flour contents while emulsion properties decreased simultaneously. The addition of plantain flour to wheat flour decreased the resistance of dough to extension (R), extensibility of dough (L) and mechanical work of dough deformation (W). Substitution of wheat flour with plantain flour depressed loaf volume, sensory acceptability of breads as well as biscuit flow and break strength. Technically, organoleptically acceptable breads and biscuits were formulated from wheat/plantain composite flours using up to 80:20 (w/w)% and 60:40 (w/w)% ratios of wheat:plantain flour as maximum acceptable levels of substitution for breads and biscuits respectively. However crispness of composite biscuits was compromised at high levels of plantain flour dilution when compared with non-blended wheat flour biscuits

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