Effect of Processing on Certain Antinutrients in Bambara Groundnut (Vigna subterranea) Cotyledons

Cotyledons of two Nigerian varieties of bambara groundnut were analysed for trypsin inhibitor activity (TIA) and polyphenols after whole beans had, in each case, been cold-soaked, hot-soaked, cold-soaked/germinated and dehulled. Another portion of beans was fermented after they had been cold-soaked, dehulled and boiled for 10 min (pretreatment), simulating the ‘dawadawa’ process. Germination made dehulling of the beans very easy, as the hulls broke open during the process, but was not very effective in reducing the polyphenol levels (9%, average loss) and TIA (17%, average loss). The combined pretreatment/fermentation process reduced the polyphenol level and TIA by 24% and 40%, respectively (average losses). Hot-soaking considerably improved the dehulling properties of the beans over cold-soaking and was more effective in reducing the TIA level in the cotyledons (31%, average loss) than cold-soaking (12%, average loss). Polyphenol losses by the two conditioning methods were similar (9%, average). Generally, losses in polyphenols and TIA could be attributed to leaching and inactivation respectively during the processes involved. The results show that a combination of two or more simple processing methods could be used to improve the food value of bambara groundnut. © 1997 SCI.     

Gelatinisation of Starch in Cowpeas (Vigna unguiculata)

The course of gelatinisation was followed during the cooking of cowpeas. Dry cowpeas were only gelatinised to the extent of 60% after 5 h cooking but pre-soaking in tap water enabled gelatinisation to be completed in this time. Soaking in polyphosphate solutions and a “kawe” solution resulted in similar marked improvement in gelatinisation rate.     

Protein and Starch Digestibility and Flatulence Potential of Germinated Cowpeas (Vigna unguiculata)

In vivo and in vitro methods with experimental rats and commercial digestive enzymes, respectively, were used in assessing the protein and starch digestibility and flatulence potential of germinated cow-peas. Germination (24 hr at 25° or 30°C) reduced the flatulence potential of seeds (52 to 77%). In vivo digestibility of starch and protein was also significantly increase by germination. Germination did not affect in vitro protein digestibility, but reduced in vitro digestibility of freeze-dried and 70°C-dried starch. Cooking in boiling water significantly increased in vitro protein and starch digestibility of both ungerminated and germinated seed.     

Effect of Dry Heat Pre-Treatment (Toasting) on the Cooking Time of Cowpeas (Vigna unguiculata L. Walp)

Four cowpea varieties (Brown beans, Oloka beans, IAR48 and IT89KD-288) were toasted at 105 °C, and used to study the effect of dry heat treatment on the cooking time and nutrient composition of cowpea seeds and also its effect on the functional properties of resultant flour of the cowpea seed varieties. Toasting reduced the cooking time for brown and oloka cowpea varieties from 55.00–31.00 and 70.67–51.67 min, respectively. The cooking time for IAR48 and IT89KD-288 cowpea varieties increased from 104.67 to 106.00 and 88.00 to 88.67 min, respectively. The results indicate that the cooking time of cowpea seeds can be reduced significantly on toasting, while maintaining their potential as functional agents in the food industry for nutrition and utilisation. Correlation between the amount of water imbibed by cowpea seeds and their cooking time was -0.74, but was not significant at p ≤ 0.05, suggesting that there is no significant relationship between the amount of water imbibed by cowpea seeds and their cooking time.     

Reversibility of the Hard-to-Cook Defect in Dry Beans (Phaseolus vulgaris) and Cowpeas (Vigna unguiculata)

The hard-to-cook defect, assumed to be a permanent condition in legume seeds, can be reversed. Dry beans (Phaseolus vulgaris) and cowpeas (Vigna unguiculata) which had developed the hard-to-cook defect when stored at 29°C, 65% RH had progressively shorter cooking times after additional storage at 6.5°C, 71% RH. This would suggest that the mechanism(s) leading to development of the defect should be easily reversed. The ability to reverse the hard-to-cook defect in legume seeds would provide several economic and nutritional benefits.     

Acceptability and Nutrient Content of Milk Substitutes from Four Cultivars of Cowpeas (Vigna unguiculata)

Milk was extracted from four cultivars of cowpeas and analysed for their nutrient content. The protein content of the milk substitutes varied from 1.2-3.0g, energy, 17.9-42.4 Kcal; total solids 4.2-10.7g and sugars from 0.2-0.6g per 100 mL. The protein digestibility was from 56.0-78.5% and trypsin inhibitor activity was 5.8-7.1 TIU/mL. The cultivars had an effect on the yields, the total solids, the energy, protein total sugars, trypsin inhibitor activity, and digestibility of the milk substitutes.     

Mineral Loss in Cowpeas [Vigna unguiculata (L.) Walp] by Pressure Heating in Water

White Acre cowpeas of four maturity levels were heated in water at 35 kPa for 0–40 min. As the cowpeas increased in maturity, Zn, Cu, Mn, Mg, and K increased, Fe decreased and Ca did not change. All minerals analyzed decreased with heating: Cu, Ca and Mg (p < 0.001), Zn, Fe and K (p <0.01) and Mn (P<0.05). Minerals leached from the cowpeas at different magnitudes and rates. For example, K lowered 70–80% within 10 min; others lowered 20% or less. Loss of minerals across maturity stages was not uniform. This method reduced loss of certain minerals when compared to published values for the boiling water method.     

An Evaluation of Marinated Southern Peas (Vigna unguiculata)

Cooked southern peas (Vigna unguiculata) of two levels of maturities were soaked in sweet- or hot-flavored marinades. Marinade treatments and maturity level of the peas affected most attributes tested. Treated peas had less moisture, protein and nitrogen-free extract and more fat, crude fiber, ash and caloric content than unmarinated peas. Luminosity was reduced, redness was varied and yellowness was increased by marinating. Firmness of marinated peas was increased. PER was not affected and averaged 1.83. pH was lowered from 6.6 to 3.9; acidity was raised from 0.1% to 1.9%. Neither treatment nor maturity affected the microbiological counts. Samples were scored as “like slightly.”     

Effect of water hardness on cooking characteristics of cowpea (Vigna unguiculata L. Walp) seeds

Cowpeas were cooked in water made hard (or soft) by the separate addition of similar concentrations of certain salts (CaCl₂, MgCl₂, or NaHCO₃). The beans were also cooked in hard tap water and in double distilled water before and after soaking in water. Hard water caused a significant decrease in softness, led to reduced water absorption, and also decreased solids loss in the cooked product, but it increased the cooking time and discolouration of the beans. Hard water also gave rise to a significant ( P <0.05) increase in mineral content, but it had less effect on the proximate composition of the cooked products.     

Effect of milling method on selected physical and functional properties of cowpea (Vigna unguiculata) paste

Particle size distribution (PSD) of cowpea meal is an important determinant of paste functionality and end product quality. Samples from various mills and screen sizes were used to determine PSD, water‐holding capacity (WHC) and swelling capacity (SWC). Hammer mill (1.73 mm screen) meal had a geometric mean diameter (d_gw) of 221 microns, whereas PM‐360 [plate mill with one complete turn (360°) of clearance] meal had a d_gw of 1559 microns. All other milling processes resulted in meal with an intermediate particle size. To reduce the particle size of cowpea pastes, cowpea meals were hydrated to pre‐determined moisture contents, held for 15 min, and then blended in a blender before whipping. Blending increased the WHC and SWC of all samples.     

紫皮豇豆(Vigna unguiculata L.)花色苷的研究

首次应用高效液相色谱-二极管阵列检测器-质谱联用技术(HPLC-DAD-MS)鉴定出紫皮豇豆主要含有三种花色苷,分别为飞燕草色素、矢车菊色素、天竺葵色素的葡萄糖苷,其中矢车菊葡萄糖苷相对百分含量达到93.4%;应用pH示差法测定出其单体花色苷的含量为57.15mg/100g鲜重;应用DPPH法测定结果显示,花色苷粗提液有较强的抗氧化能力。     

Anthocyanins in cowpea [Vigna unguiculata (L.) Walp. ssp. unguiculata]

The aim of this study was to isolate and identify the anthocyanins in the black seed coated cowpea [Vigna unguiculata (L.) Walp. ssp. unguiculata] using reverse phase C-18 open column chromatography and high performance liquid chromatography (HPLC) with diode array detection and electro spray ionization/mass spectrometry (DAD-ESI/MS) analysis, respectively. Anthocyanins were extracted from the coat of black cowpea with 1% trifluoroacetic acid (TFA) in methanol, isolated by RP-C-18 column chromatography, and their structures elucidated by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy. The isolated anthocyanins were characterized as delphinidin-3-O-glucoside (2) and cyanidin-3-O-glucoside (4). Furthermore, 5 minor anthocyanins were detected and identified as delphinidin-3-O-galactoside (1), cyanidin-3-O-galactoside (3), petunidin-3-O-glucoside (5), peonidin-3-O-glucoside (7), and malvidin-3-O-glucoside (8) based on the fragmentation patterns of HPLC-DADESI/MS analysis.     

Effect of simulated gastrointestinal digestion on phenolic composition and antioxidant capacity of cooked cowpea (Vigna unguiculata) varieties

Consumption of diets rich in phenolic compounds has been associated with reduced risk of chronic diseases. The effect of cooking and simulated gastrointestinal digestion on phenolic compounds and antioxidant properties of two cowpea (Vigna unguiculata) types was determined. Phenolic acids, flavan‐3‐ols and flavonols were the main groups of phenolic compounds identified. Cooking and simulated enzyme digestion of the cooked cowpea samples rendered some phenolics less extractable (possibly by promoting binding with other food components) or more extractable (possibly by release of bound forms). Total phenolic contents and radical scavenging properties of the cowpeas were reduced upon cooking, but increased upon simulated enzyme digestion. Cowpea extracts inhibited human LDL oxidation at a concentration of 2 mg mL^?1 possibly due to their phenolic content. Phenolic compounds in cowpea can potentially protect against cardiovascular diseases for which LDL oxidation is a risk factor.     

Physico-chemical and nutritional properties of cowpeas (Vigna unguiculata) heated under pressure

Cowpeas (Vigna unguiculata (L) Walp) at four stages of maturity were heated in water at 34.5 kPa for varying times up to 40 min. All measurements except ash were affected by the stage of maturity and time of heating. Changes occurred most rapidly during the first 10 min of heating. The greenness of the most immature cowpeas was lost. The degrees of firmness of all groups differed initially but decreased rapidly during the first 5 min and more slowly thereafter. Fresh cowpeas were softened sufficiently for eating after 10 min at which time pH increased 0.65 units to pH 6.75 and acidity decreased to 0.17%. In-vitro protein digestibility of the most mature, unheated cowpeas was 70.7% and increased to 83.4% after 10 min heating. Heating decreased the original trypsin inhibitor activity by 81.7% after 5 min and 85.9% after 10 min.     

Inheritance of protein content in seeds of selected crosses of cowpea (Vigna unguiculata)

The inheritance pattern of protein content in seeds of two crosses of cowpea (Vigna unguiculata (L) Walp) was studied. It was observed that, in both crosses, inheritance of the character involved both additive and non-additive gene effects. Heritability in the broad sense was 0·70–0·78. A significant effect of pollen source was detected in one of the two crosses. In both crosses, comparison of seed protein content of reciprocal segregating generations indicated the influence of cytoplasmic factors.     

Biochemical basis of insect resistance in Vigna unguiculata

The bruchid beetle Callosobruchus maculatus (F.) causes extensive damage to seeds of the cowpea, Vigna unguiculata (L.) (Walp.), when this important tropical foodstuff is stored. A variety of cowpea resistant to attack by this pest has been described. In the present work seeds of a number of cowpea varieties, including the resistant one, were tested for the presence of a physical resistance to C. maculatus, in terms of repulsion of oviposition or of failure of larvae to enter the seeds. No evidence to suggest the presence of a physical resistance was found. When seeds of cowpea varieties were tested for the presence of various antimetabolic secondary compounds, only inhibitory activity against trypsin and, to a much lesser extent, chymotrypsin, could be detected. The resistant variety of cowpea contained a significantly higher level of inhibitors, about twice as much as any other variety. A proteinase inhibitor active against trypsin was purified from cowpea varieties by affinity chromatography on trypsin-Sepharose. The purified inhibitor was shown to inhibit chyraotrypsin also, in such proportions as to account for chymotrypsin inhibition by seed extracts. The inhibitor was shown to consist of a number of isoinhibitors by gel electrophoresis and isoelectric focusing, but no qualitative differences in the inhibitor between varieties could be detected. The antimetabolic nature of the cowpea trypsin inhibitor was confirmed by insect feeding trials in which various protein fractions were added to a basic meal and the effect on larval survival noted. The albumin proteins of cowpea (containing the trypsin inhibitors) at a level of 10% were toxic to larvae of C. maculatus whereas the globulin fractions were not. Further, if cowpea trypsin inhibitor was removed from the albumin proteins they ceased to be toxic. When purified cowpea trypsin inhibitor was added to the basic meal it was shown that a level slightly less than that found in the resistant variety of cowpea caused complete mortality of larvae, whereas lower levels had lesser or no effect. It is concluded that this example of insect resistance in the cowpea is due to an elevated level of trypsin inhibitor.     

Quality of Main-moins Prepared from Whole or Dehulled Cowpea (Vigna unguiculata) Cultivars

Mom-moins, steamed cowpea (Vigna unguiculata) products, made from Texas Cream and Chinese Red peas were evaluated and compared to those from California Blackeye peas (control). Sensory evaluation by 11 West African panelists showed that good quality moin-moins could be prepared from the investigated cowpea cultivars if dehulled. Only Texas Cream pea cultivar produced good quality moin-moin from the whole peas, thus making the strenuous dehulling process unnecessary. Moin-moins made from Texas Cream peas also had higher protein and ash contents. Agtron values were positively correlated (p < 0.01) to the sensory color scores.     

Changes in Oligosaccharide Content, Enzyme Activities and Dry Matter during Controlled Germination of Cowpeas (Vigna Unguiculata)

Cowpeas were germinated at 25, 30, and 35°C for 12, 24, 48, and 72 hr. Stachyose disappeared after 48 hr germination at 30°C while 85 and 95% reductions occurred at 35°C for 48 and 72 hr. respectively. Total oligosaccharide reduction was significantly greater at 30°C than at 25°C. Protease and amylase activities and rootlet development were minimal after 24 hr germination but increased thereafter. Anerobic incubation was ineffective in furthering reduction of olicosaccharides in seeds germinated at 25 or at 30°C for 12 or 24 hr. Total protein and carbohydrate contents were relatively unaffected.     

Nutrient Quality of Corn and Sorghum Supplemented with Cowpeas (V. unguiculata) in the Traditional Manufacture of Ogi

Protein in ogi, a fermented cereal food common in Nigeria, prepared from 100% corn increased from 9.1g to 13.1 and 14.4g in ogi supplemented with 30% and 40% cowpea, respectively. Similarly, protein in ogi from 100% sorghum increased from 7.lg to 8.4g for ogi at 30% and 11g at 40% cowpea supplementation. A 100% acceptability score was obtained for ogi made from 70% corn supplemented with 30% dehulled cowpea. An acceptability score of 70% was obtained for ogi from 70% sorghum or corn and 30% dehulled cowpea. However, ogi from 60% sorghum or corn and 40% whole cowpea was least acceptable with a score of 20%.     

Functional Properties of Raw and Heat Processed Cowpea (Vigna unguiculata, Walp) Flour

The functional properties, gelation, water and oil absorption, emulsification, foaming and protein solubility of raw and heat processed cowpea flour were determined. The effects of pH and NaCl concentration on some of these functional properties were also investigated. Protein solubility vs pH profile showed minimal solubility at pH 4. Water and oil absorption capacities of raw flour were 2.4 g/g and 2.9 g/g, respectively, while heat processed flour gave 3.6 g/g and 3.2 g/g, respectively. Addition of NaCl up to 0.4% improved the emulsification capacity of raw flour while a decrease was observed in the heat processed flour after 0.2%. Least gelation concentration of raw flour was found to be 16% and heat processed flour, 18%.