Cowpea flour was used to replace 30% of plantain flour to obtain ... Blends of CPF and wheat flour (WF) were prepared and evaluated for their functional.
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Plant Foods for Human Nutrition 58: 1–8, 2003. C 2003 Kluwer Academic Publishers. Printed in the Netherlands.
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Functional Properties and Performance of Cowpea/Plantain/Wheat Flour Blends in Biscuits PETER I AKUBOR Department of Food Science and Technology, Federal Polytechnic, P.M.B 1037, Idah, Nigeria
Abstract. Cowpea flour was used to replace 30% of plantain flour to obtain cowpea/plantain flour (CPF) blends. Blends of CPF and wheat flour (WF) were prepared and evaluated for their functional properties. Biscuits were prepared from CPF/WF blends and their protein contents, physical and sensory properties were determined. The water and oil absorption capacities of the CPF/WF blends increased with increased amount of CPF in the blends. The bulk density did not differ ( p > 0.05) among the CPF/WF blends. The foaming properties of CPF were improved by the incorporation of WF. Foams prepared from the blends were time stable; stability values ranged from 64 to 94%. The emulsifying activity and emulsion stability of the CPF/WF blends were low. The protein contents of the CPF/WF ranged between 15.2 and 18.9%; values increased with increased levels of CPF in the blend. The thickness, diameter, weight and spread ratio did not differ significantly ( p > 0.05) among the CPF/WF biscuits. At all levels of CPF substitution, the CPF/WF biscuits were statistically similar ( p > 0.05) Sensory ratings for color flavor, texture and overall acceptability. The sensory scores for color, flavor, and texture of the CPF/WF biscuits were not significantly ( p > 0.05) different from those of 100% WF biscuit (control). The CPF/WF biscuits were generally accepted. Key words: Blends, Biscuits, Functionality, Physical Evaluation, Sensory Quality, Supplementation
Introduction Plantains (Musa Paradisiaca) are abundant in Nigeria and other developing countries. In such areas, plantains are used in various food formulations which are compatable with the local tastes and habits. Because plantains are rich in carbohydrate but poor in protein, people who eat much of plantain products are prone to malnutrition. However, the proteins of plantains could be supplemented with legume protein. The resulting products would be rich in both protein and carbohydrates. Supplementation of flours in Nigeria has included the use of soybeans, groundnuts, pigeon peas and cowpeas. A protein supplement should be cheap and readily available, and should possess satisfactory nutritional and functional properties. Cowpeas (Vigna unguiculata L) are grown extensively and sold at affordable prices in Nigeria. They are rich in protein with a good balance of amino acids. Thus, a cowpea/plantain blend would provide a nutritionally balanced food for both infants and adults because of the expected improved protein quality as well as abundant energy content. An earlier report showed that cowpea/plantain flour blends had some functional properties which would lend them to use in bakery products (1). The report showed that cowpea and plantain flours can be combined to produce acceptable cookies with good physical and sensory qualities and improved
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2 nutritional quality with respect to wheat flour cookies. In another study, it was shown that cowpea flour could be substituted for 80% of the wheat flour in biscuits without adversely affecting product quality (2). Several studies have shown that biscuits prepared by partial substitution of wheat with non-wheat flours have gained wide acceptance in Nigeria (3, 4, 5, 6) This is an advantage in a non-traditional. wheat producing country like Nigeria. Biscuits are an important component of the Nigerian diet. Biscuits could provide an excellent means of improving nutritional quality through incorporation of vegetable proteins. Plantains are used as an inexpensive source of calories. A cowpea/plantain/wheat flour blend could become a functional ingredient as well as a vegetable protein source. Such extended use of the blends would depend on the knowledge of their functional properties. However, the only conclusive test for the functionality of a cowpea/plantain flour blend is to use it as an ingredient for the preparation of a finished product. Therefore, the objectives of this work were to determine the functional properties of cowpea/plantain/wheat flour blends, and to determine the protein content, and physical and sensory properties of biscuits prepared from the blends.
Material and Methods About 50kg of mature, healthy, unripe plantains (Musa paracisiaca), the large brown eye Kano white variety of cowpea (Vigna unguiculata L) seeds (50 Kg) and commercial wheat flour (10 Kg) were purchased from a local market in Idah town, Kogi State, Nigeria. The plantain fruits were stored in a refrigerator at 10 ± 2 ◦ C. The cowpea seeds were stored in jute bags at 30 ± 2 ◦ C. The wheat flour was heat sealed in high density polyethylene bags until used. Plantain Flour Each of the plantain fruits was washed in tap water, hand peeled and the edible portion was sliced with a stainless knife into thin slices (1 mm thick). The slices were soaked in sodium metabisulphite solution (0.25g/L) for 10 min. The slices were drained within 5 min in a basket and then dried in a conventional hot air oven (GallenKamp & Co, Ltd London) at 50 ◦ C to 8% moisture. The dried slices were milled in a hammer mill (Model RLA 201 - 80014, UK) to pass through a 40 mesh sieve (British standard). Cowpea Flour The cowpea seeds were cleaned of dust and other extraneous material. The seeds were soaked in excess tap water (30 ± 2 ◦ C, 30 min) in a basin. The hydrated seeds were dehulled mannually and the loosened hulls were floated off the kernels. The kernels were washed in tap water, dried in a conventional hot air oven (Gallenkamp & Co, Ltd, London) at 50 ◦ C to 8% moisture and milled
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3 in a hammer mill (Model RLA 201-80014, UK) to pass through a 40 mesh sieve. Flour Blending The cowpea flour (70%) was blended with plantain flour (30%) in a Kenwood food blender (Model KM 201, England) operated at full speed for 5 min. This was designated as cowpea/plantain flour (CPF) blend. Wheat flour (10, 15, 20, 25, 30, 40, 50 and 60%) was blended with the CPF blend on a replacement basis in a Kenwood food blender operated at full speed for 5 min. The flour blends were packed in high density polyethylene bags and stored in a refrigerator until used. Evaluation of Functional Properties Packed bulk density was determined as described by Okaka and Potter (3) and expressed as g/cm3 . Foaming capacity (FC) and foam stability (FS) were determined as described by Narayana and Narasinga Rao (7). The volume of foam at 60 seconds after whipping was expressed as FC. The foam volume was recorded 1 h after whipping to determine FS as percent of the initial foam volume. The emulsion activity and emulsion stability were determined as described by Yasumatsu et al. (8). The water and oil absorption capacities were determined by the methods of Sosulski et al. (9), and values expressed as percent water or oil absorbed by 1 g flour. Preparation of Biscuits Biscuits were prepared according to the formula of Nishibori and Kawakishi (10) with slight modifications. Sucrose and margarine were used in place of glucose and butter in the original formula (5). The basic formulation used was 49.5% flour, 20% margarine, 10% heaten whole egg, 20% sucrose and 0.5% baking powder. The dry ingredients were weighed and mixed thoroughly. Margarine was added and rubbed in until uniform. The egg was added and dough thoroughly kneaded on a flat clean stainless metal table for 5 min. The dough was thinly rolled on a sheeting board to uniform thickness (0.8 cm) and cut using a round cutter to a diameter of 3.0 cm. The dough pieces were baked in greased pans at 160 ◦ C for 15 min in an air oven (F1: Model 4 BF, Germany), cooled at room temperature for 2h and then packed in high density polethylene bags (0.70 mm thick). Chemical and Physical Evaluation of Biscuits The MicroKjeldahl method (11) was used for the determination of protein (N × 6.25). Biscuit diameter (D) and thickness (T) were measured with a Vernier caliper. Weights were determined using a Mettler digital top loading balance (Mettler, PC 400, Switzerland). Spread ratio was calculated as D/T. The average values of 3 determinations were reported.
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4 Sensory Evaluation The biscuit samples including the 100% wheat flour and the 100% cowpea/plantain flour blend (controls) were evaluated for color, flavor, texture and overall acceptability using a preference method. Twenty untrained panelists, who were familiar with biscuit quality attributes, were randomly selected from staff and students of the Federal Polytechnic, Idah community. The samples were evaluated on a 5-point hedonic scale (1 = disliked extremely, 5 = liked extremely). The samples were assigned three digit – codes and presented to judges on white plates in a fluorescent – lighted sensory evaluation laboratory. The order of presentation of samples to the panel was randomized. The tests were performed at 10 a.m. in the morning. Tap water was provided for the judges to rinse their mouths between evaluations. Statistical Analysis Data were analyzed by analysis of variance (12). Means were separated by least significant difference (LSD) test. Significance was accepted at p ≤ 0.05. Results and Discussion Functional Properties The functional properties of cowpea/plantain flour (CPF), wheat flour (WF) and their blends are presented in Table 1. The CPF showed a better ability to absorb and retain oil than the WF. On the other hand, the WF had a higher water absorption capacity than CPF. The oil and water absorption capacities of the CPF/WF blends increased with increased levels of CPF in the blends. The water absorption capacity of the CPF/WF blends were higher than those of the individual CPF and WF. However, the CPF/WF blends had lower oil absorption capacity than that of CPF. These properties give an advantage to the blends over the individual WF and CPF in baked products where hydration to improve handling characteristics is required and in products such as doughnuts and pancakes where oil holding property is an important consideration. In baking, the CPF/WF protein’s resistance to oil absorption is important in creating a light product. The foaming property determined as foaming capacity (FC) and foam stability (FS) of CPF were improved by the incorporation of WF. The FC of CPF increased from 20 to 23.3% at the highest level of WF addition. The FS showed a similar trend as the FC. The foams prepared from the blends were stable, FS values were between 63 and 94%. These values were higher than a range of 60–73% reported for cowpea/plantain flour blend (6). Okaka and Potter (3) suggested that the superiority of soyflour to cowpea in foaming property was due to the higher protein content of soyflour. However, earlier reports showed that foam formation
100:0
0:100
85:15
98 ± 0.2b
92 ± 022c
110 ± 0.1b
80:20
90 ± 0.1cd
106 ± 0.1c
75:15
88 ± 0.8cd
103 ± 0.12c
70:30
31.3 ± 0.1b 33.5 ± 0.1b 33.6 ± 0.2b 31.3 ± 0.1b 23.3 ± 0.4b 94 ± 0.8a 88 ± 0.b 80 ± 0.4c 75 ± 0.4d 71 ± 0.8e 0.84 ± 0.2a 0.83 ± 0.1b 0.85 ± 0.1 0.83 ± 0.2 0.84 ± 0.4 10 ± 0.4a 8 ± 0.2a 8 ± 0.7a 5 ± 0.8b 4 ± 0.4b 6 ± 0.7a 5 ± 0.8a 6 ± 0.9a 4 ± 0.8a 5 ± 0.1a
101 ± 0.3a
199 ± 0.2a 117 ± 0.4a
80:10
80 ± 0.7f
86 ± 0.8e
50:50
PLSD
3.0 4.0 8.0 3.5 2.0
73 ± 0.1g 2.0
74 ± 0.4f 3.0
40;60
31.3 ± 0.8b 31.3 ± 0.7b 33.3 ± 0.6b 69 ± 0.8e 63 ± 0.9f 64 ± 0.8f 0.85 ± 0.8 0.83 ± 0.3 0.83 ± 0.9 4 ± 0.4b 3 ± 0.8b 2 ± 0.4b 3 ± 0.8b 5 ± 0.6a 6 ± 0.3a
84 ± 0.4e
98 ± 0.8a
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Note. Means ± SD of 3 determinations. Means within a row with the same superscript were not significantly different ( p > 0.05). LSD Least Significant Difference. CPF was prepared from 70:30 (Cowpea:Plantain.) ratio.
Water absorption 71 ± 0.1g 75 ± 0.1f capacity (%) Oil absorption 115 ± 0.2a 196 ± 0.3b capacity (%) Foam capacity (%) 20 ± 0.1 40 ± 0.1a Foam stability (%) 62 ± 0.2 78 ± 0.1d Bulk density (g/cm) 0.63 ± 0.1 0272 ± 0.1d 5 ± 0.1b Emulsion activity (%) 7.0 ± 0.1a Emulsion stability (%) 10.0 ± 0.0 4 ± 0.1a
Property
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Table 1. Functional Properties of Cowpea/plantain Flour (CPF), Wheat Flour (WF) and their blends
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6 and foam stability are a function of the types of protein, pH, processing method, viscosity and surface tension (8). Foams are used to improve texture, consistency and appearance of foods. The foaming properties of CPF/WF blends lend them to some potential end uses in baked and confectionary products. The incorporation of WF into CPF caused no significant effect ( p > 0.05) on the bulk density of the resulting blends. The bulk density of WF and CPF were 0.72 and 0.63 g/cm3 , respectively, and varied from 0.83 to 0.85 g/cm3 for. the blends. Flour blends with similar bulk densities as the CPF/WF were recommended for formulation of supplementary foods (13, 6, 14). The bulk density of a flour can be used to determine its packaging requirements. The emulsion activity of CPF was 2% greater than that of WF. The CPF/WF blends showed low emulsion activity and stability. The WF, CPF and their blends would not be useful in preparing mayonnaise, salad dressing, and milks because of the emulsion requirement of these products.
Protein Content and Physical Properties The protein and physical properties of biscuits prepared from cowpea/plantain flour (CPF), wheat flour (WF) and their blends are presented in Table 2. The CPF and WF biscuits contained 19.8 and 13.4% protein, respectively. The protein contents of the CPF/WF biscuits ranged between 15.2 and 18.9%; values decreased with increased levels of WF in the blends. The observed trend was probably due to an addition effect since CPF had higher protein content than that of the 100% WF biscuit. Although the protein quality of the biscuits was not evaluated in this study, the CPF/WF blended bsicuits would be better than those of the individual CPF and WF Table 2. Protein content and physical properties of biscuits prepared from cowpea/plantain flour (CPF), Wheat flour (WF) and their blends Measurement CPF:WF
Protein (%)
Thickness (Cm)
Diameter (cm)
Weight (g)
Spread ratio
100:0 0:100 90:10 85:15 80:20 75:25 70:30 60:40 50:50 40:60 LSD
19.8 ± 0.34a 13.4 ± 0.21e 18.9 ± 0.10ab 18.5 ± 0.45ab 18.3 ± 0.39abc 17.9 ± 0.41abc 17.4 ± 0.25c 16.8 ± 0.14cd 16.0 ± 0.01d 15.2 ± 0.81d 1.0
1.1 ± 0.21a 1.1 ± 0.08a 1.1 ± 0.35a 1.2 ± 0.41a 1.2 ± 0.37a 1.1 ± 0.29a 1.1 ± 0.09a 1.2 ± 0.01a 1.1 ± 0.24a 1.2 ± 0.35a 0.40
3.6 ± 0.01a 3.7 ± 0.36a 3.7 ± 0.21a 3.8 ± 0.30a 3.7 ± 0.47a 3.6 ± 0.17a 3.7 ± 0.05a 3.7 ± 0.11a 3.6 ± 0.52a 3.7 ± 0.71a 0.80
8.7 ± 0.81a 7.4 ± 0.30ab 7.2 ± 0.24ab 7.9 ± 0.14ab 7.4 ± 0.37ab 7.4 ± 0.66ab 7.1 ± 0.90ab 7.8 ± 0.08ab 7.3 ± 0.84ab 7.6 ± 0.39ab 0.11
3.3 3.4 3.4 3.2 3.1 3.3 3.4 3.1 3.3 3.1
Note. Means ± SD of 3 determinations. Means within a column with the same superscript were not significantly different ( p > 0.05) LSD, Least Significant Difference. CPF was prepared from 70:30 (Cowpea: Plantain) ratio.
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7 biscuits because of the expected complementation between the proteins of cowpeas, plantains and wheat (15). At all levels of WF substitution, biscuits showed no significant ( p > 0.05) difference in thickness and diameter. The thickness and diameter of the CPF/WF biscuits ranged from 1.1 to 1.2 cm and 3.6–3.8 cm, respectively. The weight of the CPF and WF biscuits were 8.7 and 7.4 g, respectively, and varied from 7.1 to 8.2 g for the CPF/WF biscuits. The CPF biscuit had the highest weight among the biscuits studied. However, the spread ratio did not vary among the biscuits. Spread ratio is affected by the competition of ingredients for available water (16). Ingredients which absorb water during mixing will reduce it. Laughton and Pearce (16) reported a reduction in spread ratio of biscuits when the enrichment levels with sunflower protein isolates were increased. The results of this study did not agree with the observation of Laughton and Pearce (16). The water absorption capacity of CPF/WF increased with increased level of CPF in the blend. However, the spread ratio was not affected by the increased levels. It appears that other functional properties besides water absorption may also affect spread. Sensory Evaluation The mean sensory ratings for biscuits prepared from wheat flour (WF), cowpea/plantain flour (CPF) and their blends are presented in Table 3. The WF, CPF and the CPF/WF biscuits showed statistically ( p > 0.05) similar sensory ratings for flavor and color. However, the biscuits differed significantly in their scores for texture and overall acceptability. The CPF biscuits received the lowest scores for texture. The panelists considered the biscuits to be hard to bite. Gas retention is Table 3. Sensory mean scores of biscuits prepared from cowpea/plantain flour (CPF), wheat flour (WF) and their blends Sensory attribute CPF:WF
Color
Flavor
Texture
Overall acceptability
100:0 0:100 90:10 85:25 80:20 75:25 70:30 60:40 50:50 40:60 LSD
3.13 ± 0.4b 4.63 ± 0.5a 3.75 ± 0.6b 3.88 ± 0.7b 3.25 ± 0.4b 3.13 ± 0.1b 3.50 ± 0.2b 3.75 ± 0.3b 3.25 ± 0.2b 3.63 ± 0.1b 1.0
3.75 ± 0.1a 3.75 ± 0.2a 3.25 ± 0.3a 3.75 ± 0.2a 3.75 ± 0.8a 3.75 ± 0.7a 3.88 ± 0.8d 3.75 ± 0.4a 3.50 ± 0.1a 3.50 ± 0.2a 0.9
3.38 ± 0.2b 4.25 ± 0.1a 3.75 ± 0.8a 3.88 ± 0.4a 3.63 ± 0.5a 3.63 ± 0.4a 3.50 ± 0.3a 3.88 ± 0.4a 3.50 ± 0.5a 3.58 ± 0.1a 0.95
3.63 ± 0.1b 4.38 ± 0.2a 3.38 ± 0.3b 3.38 ± 0.3b 3.33 ± 0.4b 3.50 ± 0.2b 2.28 ± 0.1b 3.30 ± 0.2a 3.38 ± 0.3b 3.38 ± 0.2b 0.5
Note. Mean ± SD within a column with the same superscript were not significantly different ( p > 0.05). + evaluated on a 5-point hedonic scale. (1 = disliked extremely, 5 = liked extremely), (LSD) Least significant difference. CPF was prepared from 70 : 30 (Cowpea:Plantain) ratio.
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8 a property of wheat protein (gluten). During dough development, the gluten becomes extensive and strong. This allows the dough to rise and also prevents easy escape of the gas during baking, thus, providing an open and porous texture for the baked product. This property was absent in the CPF and appears to account for the hard texture of the CPF biscuit. With respect to overall acceptability, the 100% WF biscuit was rated higher than the other biscuits. All the CPF/WF biscuits were generally acceptable. In conclusion, these results demonstrated that cowpea/plantain flour (CPF) and wheat flour (WF) can be combined to produce acceptable biscuits with good physical and sensory qualities with improved nutritional quality. CPF could substitute upto 90% WF without adversely affecting product quality. The protein content increased from 13.4% for the 100% WF biscuit to 18.9% for CPF/WF biscuit with the highest level of WF substitution. This is an advantage in a non-traditional wheat producing country like Nigeria.
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