R. Dixon Phillips

Utilization of cowpeas for human food

Abstract This paper reviews the research and outreach accomplishments of the cowpea utilization project sponsored by the United States Agency for International Development-funded Bean/Cowpea Collaborative Research Support Program. Research has examined a limited number of cultivars and has taken as its starting point mature, dry seeds. A broad spectrum of food quality issues have been studied, including: • safety concerns and physiological effects associated with consuming legume seeds and products made from them; • chemical composition and nutritional quality of the seeds and products; • physical and functional behavior of seeds and products; and • socioeconomic aspects including sensory quality of seeds and products, consumer acceptance, and costs and impacts of technology adoption. Research foci have included: • The effect of pretreatment and storage on cowpea food quality; • processing whole seeds to improve food quality; • conversion of legume seeds into food ingredients, principally flours and meals; • processing seeds and ingredients to improve food quality; and • improvement of traditional foods and development of new foods from bean and cowpea-based ingredients.

Commercial Runner Peanut Cultivars in the United States: Tocopherol Composition

Tocopherols in commercially grown normal, mid- and high-oleic Runner peanuts from 2005 and 2006 were quantified to give accurate vitamin E contents. Tocopherols were extracted from raw peanuts by a direct solvent extraction procedure using 10% ethyl acetate in hexanes that provided percent recoveries of 105.4, 101.2, 103.9, and 102.8 for alpha-tocopherol (T), beta-T, gamma-T, and delta-T, respectively. No significant (P > 0.05) differences were noted in total tocopherol levels in normal- (22.4 mg/100 g), mid- (23.9 mg/100 g), and high-oleic (22.4 mg/100 g) Runner peanuts. alpha-T levels did vary significantly among the Runner cultivars classified by their oleic acid content (mid, 11.7 mg/100 g; normal, 10.9 mg/100 g; high, 9.8 mg/100 g). Cultivar effects were highly significant (P < 0.001) for alpha-, beta-, gamma-, and delta-T and total tocopherol contents, whereas production year effects were highly significant for alpha- and beta-T levels. Year x cultivar interactions were not significant (P > 0.05). Cluster analysis segregated the cultivars into two major groups represented by lower alpha-T and higher gamma-T levels (cluster A) and high alpha-T and low gamma-T levels (cluster B) (P < 0.05). The mean alpha-T level in Runner peanuts (151 samples) was 10.5 +/- 1.5 mg/100 g, which is 26.7% greater than the imputed value for peanuts, all types (NBD 16087) provided by the USDA National Nutrient Database for Standard Reference.

Commercial peanut (Arachis hypogaea L.) cultivars in the United States: phytosterol composition.

Phytosterols in commercially grown Runner, Virginia, and Spanish peanuts (n = 221) from 2005 and 2006 were quantified by a combination of acid hydrolysis and alkaline saponification steps followed by gas chromatography-flame ionization detection and gas chromatography-mass spectrometry analysis of the trimethylsilyl derivatives. Δ(5)-Avenasterol, which partially degrades during acid hydrolysis, was quantified after alkaline saponification plus direct analysis of the steryl glucosides isolated by solid-phase extraction. β-Sitosterol, Δ(5)-avenasterol, campesterol, and stigmasterol were identified in peanut lipid extracts as the dominant sterols by retention time mapping and mass spectra with recoveries ∼99%. Clerosterol, Δ(5,24(25))-stigmastadienol, Δ(7)-sitosterol + cycloartenol, and one unidentified sterol were also present but at low levels. Free and esterified phytosterols accounted for ∼80% of the total sterols determined; the remainder was attributed to steryl glucosides. The total sterol level in Spanish market type peanuts (144.1 ± 5.3 mg/100 g) was significantly greater than both Runners (127.5 ± 6.3 mg/100 g) and Virginias (129.3 ± 6.9 mg/100 g) (P < 0.05). Tamspan 90 (146.9 mg/100 g) followed by OLIN (138.5 mg/100 g) showed the highest total sterol content among the cultivars examined. Cultivar effects were strongly significant (P < 0.001) for all phytosterols, whereas production year effects were strongly significant (P < 0.001) for Δ(5)-avenasterol, Δ(5,24(25))-stigmastadienol, and the combined quantities of Δ(7)-sitosterol + cycloartenol, which coeluted. Cultivar × year interactions were strongly significant (P < 0.001) in all sterols except for Δ(7)-sitosterol + cycloartenol (P < 0.01). Total phytosterol contents were markedly higher than those reported in the existing literature for Runner and Virginia type peanuts, partially attributed to the inclusion of steryl glucosides in the analysis.

Survival and growth of acid-adapted and unadapted Shigella flexneri in a traditional fermented Ghanaian weaning food as affected by fortification with cowpea

Shigellae are among the major causes of diarrheal diseases in infants and young children in developing countries. We conducted a study to determine the effect of fermentation of corn and corn/cowpea doughs used to prepare a traditional weaning porridge on the survival and growth characteristics of acid-adapted and unadapted Shigella flexneri. Porridges were prepared from doughs fermented for 0, 24, and 48 h at 30 degrees C. Four-strain mixtures of acid-adapted and unadapted S. flexneri cells were separately inoculated (10(4)-10(5) and 10(6)-10(7) cfu/ml) into porridges made from unfermented (pH 5.74-6.05) and fermented (pH 4.07-4.38) doughs. Viability of acid-adapted cells was retained at higher levels in porridge made from fermented dough, compared to unfermented dough, regardless of composition of the porridge or incubation temperature. Cells inoculated into the porridges containing fermented dough were not detected (<1 cfu/ml) within 4 h at 48 degrees C. Results indicate that prior exposure of cells to acid stress renders them more resistant to subsequent acidic conditions. The addition of cowpea flour to corn dough followed by fermentation had little effect on the survival of S. flexneri in porridges made from the dough.

Amino acid composition protein quality and water-soluble vitamin content of germinated cowpeas (Vigna unguiculata)

Amino acid composition, protein digestibility, calculated protein efficiency ratio (C-PER and DC-PER), chemical scores and water-soluble vitamin content of cowpea seeds germinated at 25°C or 30°C for 24h were determined. Also, the effect of processing steps (heated-air drying, decortication and cooking) on these parameters were examined. Germination had little effect on amino acid profile of cowpeas. In vitro protein digestibility was not improved significantly by germination nor by decortication but was improved by cooking. C-PER and DC-PER ranged from 1.95 to 2.21 and from 1.63 to 1.82, respectively. DC-PER compared well withreported rat PER of cowpea products and seemed more sensitive than C-PER. Based on whole egg values, chemical scores ranged from 37.7 to 45.8% (mean±SD; 42.2±2.4%). Germination increased the contents of niacin, thiamin and riboflavin significantly. Decortication resulted in up to 30% loss in niacin while thiamin content was reduced 41% by cooking.

Composition and flatulence-producing potential of commonly eaten Nigerian and American legumes

Sixteen samples of dry, mature legume seeds representing eight species purchased in markets either in Port Harcourt, Nigeria, or Griffin, GA, were cooked in boiling water until tender and freeze-dried along with cookwater. Flatulence potential measured as ml H2 produced per gram of legume solids consumed was measured with rats housed in glass life-support chambers designed to collect hydrogen while supplying oxygen and absorbing water and carbon dioxide. Hydrogen was quantified by GLC using a molecular sieve column. Mono-, di- and oligosaccharides were determined by HPLC. Starch content was measured as glucose in a YSI analyzer and digestibility was determined in vitro with pancreatic amylase. Hydrogen production was positively correlated with contents of xylose and fructose as well as stachyose and an unknown thought to be verbascose, not correlated with raffinose, and negatively correlated with galactose and indigestible starch.

A method for the rapid, automated filtration of protein hydrolyzates.

Abstract A method for the automated filtration of protein hydrolyzates prior to amino acid analysis is described. Minor modification of a Technicon Sampler II enables it to function simultaneously as a sampler and a filtrate collector. Samples are drawn from cups in the sampler tray and are forced through a Teflon filter (pore size, 0.2 μm) in a Millipore Swinnex filter holder by a variable-speed Technicon proportioning pump. The filtrates are collected in cups in the sampler tray opposite those containing unfiltered hydrolyzates. Using this technique, 12 hydrolyzates can be filtered in 25 min compared to the approximately 2 h of technician time required for their manual filtration. Aliquots from each of 48 samples representing different proteins and hydrolysis conditions are filtered manually and by the automated technique. Analysis of variance of the resulting recoveries of each amino acid indicate little likelihood of effects due to filtration method.

An apparatus for rapidly preparing protein samples for hydrolysis

Abstract A device is described which allows 12 samples to be prepared for acid hydrolysis in approximately 1 h. Screw-cap test tubes containing the weighed samples are placed into the apparatus along with 6 n HCl reagent. Air is removed rapidly and simultaneously from samples and reagent by alternate evacuation and nitrogen flushing. Reagent is measured into the sample tubes, and caps are threaded into place under a nitrogen atmosphere.