Protein quality of raw and autoclaved cowpeas: Comparison between some insect resistant and susceptible varieties

Abstract

A comparative study was conducted with four improved cowpea (2 pod bug resistant and 2 susceptible) varieties to assess the effect of autoclaving at 105 degrees C under 15 psi for 30 min on their protein quality, as measured by the levels of some antinutritional factors and performance of rats fed the different cowpea diets. Also, the relationships between antinutrients in the cowpeas and protein quality indicators were examined. Results showed that autoclaving completely eliminated trypsin inhibitor, hemagglutinin and HCN, whereas it reduced significantly (p < 0.01) the levels of phytic and tannic acids in the cowpeas. In both raw and autoclaved forms, the insect susceptible cowpeas were better (p < 0.05) utilized than their resistant counterparts, a condition which was attributable to lower levels of antinutrients in the susceptible varieties. In the raw cowpeas, trypsin inhibitor, hemagglutinin and HCN were significant variables affecting cowpea protein utilization, while in autoclaved samples, tannic and phytic acids were important though nonsignificant (p > 0.05) factors. It was concluded that autoclaving at the above temperature and time improved the protein quality of the insect susceptible more than the insect resistant cowpea varieties.

Factors Influencing the Quality of Dietary Proteins: Implications for Pulses

“…Rats and chickens fed autoclaved faba beans had increased weight gain and greater gain-to-feed ratios compared with those fed control diets. Similar results have been found in cowpea, for which autoclaving at 105°C for 30 min abolished the activity of both trypsin inhibitors and hemagglutinins (Umoren et al 1997). In addition to inactivation of the antinutritive factors, heating is capable of altering the amino acid composition of protein sources, particularly by reducing available lysine content (del Cueto et al 1960;Srihara and Alexander 1983).…”

In vitro and in vivo digestibility of the albumin and globulin fractions of eight Brazilian cowpea [Vigna unguiculata (L) Walp] cultivars

“…Nell and collaborators 9 found that the true protein digestibility of autoclaved cowpea meal was 76 ± 2.2% which did not differ significantly from 73 ± 2.2% found for untreated cowpea meal. Similar values were reported by Elias et al 10 Cowpea seeds have heat-labile antinutritional substances such as protease inhibitors and lectins 6,11,12 that are responsible for diminishing protein digestibility. 13 However it has been observed that although the heat-treatment of several cowpea cultivars improved some of the nutritional parameters it was not sufficient to promote a regular animal growth when the seed meal was incorporated into diets for rats.…”

“…These authors suggested that the presence of antinutritional factors would account for the observed changes. According to a recent study undertaken by Umoren and collaborators, 6 only trypsin inhibitor has a significantly depressing effect on weight gain of rats fed a diet containing raw cowpea, whereas lectin, tannic acid, HCN and phytic acid did not have a significant effect. Hernandez et al 35 attributed the reduced digestibility of cowpea globulin to its higher trypsin inhibitor content over that of albumin.…”

Impact of Processing on the Protein Quality of Pinto Bean (Phaseolus vulgaris) and Buckwheat (Fagopyrum esculentum Moench) Flours and Blends, As Determined by in Vitro and in Vivo Methodologies

“…The animals provided the untreated pinto flour and the untreated buckwheat/pinto blend were unable to complete the study due to feed refusal. This was most likely due to the presence of antinutritive factors present in untreated beans such as proteolytic inhibitors, , hemagglutinins, and tannins, which would have been destroyed or inactivated by the extrusion and baking process. , The amino acid scores for the remaining ingredients are presented in Table . The amino acid score of buckwheat increased after extrusion, with the limiting amino acid remaining leucine.…”

“…This system is commonly used in the production of cereals, snacks, and pastas. This process has been shown to have no effect on protein content, , but can alter amino acid composition of beans. − Additionally, extrusion can increase protein digestibility of beans, possibly through reducing the activity of trypsin inhibitors. ,, Although there have been few studies determining the effects of baking on plant protein quality directly, the use of autoclaving as a surrogate of heat treatment is relatively common. − With autoclaving, a reduction in lysine content of approximately 10% was noted for chickpeas treated for 1 h . A previous investigation of plant protein blends found a significant reduction in lysine content after as little as 5 min of exposure to heating at 121 °C .…”