Physicochemical, nutritional, and microstructural characteristics of chickpeas (Cicer arietinum L.) and common beans (Phaseolus vulgaris L.) following microwave cooking

Microwave cooking of legumes such as chickpeas and common beans was evaluated by assessing the cooking quality (cooking time, firmness, cooking losses, and water uptake) and the physicochemical, nutritional, and microstructural modifications in starch and nonstarch polysaccharides. Compared to conventional cooking, microwave cooking with sealed vessels enabled a drastic reduction in cooking time, from 110 to 11 min for chickpeas and from 55 to 9 min for common beans. The solid losses, released in the cooking water, were significantly less after microwave cooking than after conventional cooking (6.5 vs 10.6 g/100 g of dry seed in chickpeas and 4.5 vs 7.5 g/100 g of dry seed in common beans). Both cooking procedures produced a redistribution of the insoluble nonstarch polysaccharides to soluble fraction, although the total nonstarch polysaccharides were not affected. Increases in in vitro starch digestibility were similar after both cooking processes, since the level of resistant starch decreased from 27.2 and 32.5% of total starch in raw chickpeas and beans, respectively, to about 10% in cooked samples and the level of rapidly digestible starch increased from 35.6 and 27.5% to about 80%. SEM studies showed that the cotyledons maintained a regular structure although most of the cell wall was broken down and shattered by both cooking procedures. In addition, the ultrastructural modifications in the cotyledon's parenchima and cells are consistent with the chemical modifications in NSP and the increase in starch digestibility after cooking.     

Protein quality and antinutritional factors in wild and cultivated species ofVigna spp

The nutritional quality of wild and cultivated species ofVigna has been evaluated. Wild species showed significantly higher protein content (P<0.01), antitryptic activity (P<0.005) and tannin content (P<0.025) and significantly lower protein digestibility (P<0.005). No significant differences were found with regard to protein quality, measured as chemical score corrected by the digestibility; sulphur amino acids turned out to be limiting in both groups. In addition no correlations were found between sulphur amino acids and protein levels, or between sulphur amino acid and trypsin inhibitor levels.Selected lines showed an improvement from the nutritional point of view linked to lower antitryptic factors and tannin content, which may give rise to a decreased resistance to pests. For all the properties considered, whether physical or biochemical, wild samples presented wider variations and the types considered most primitive were those that differed most from the cultivated ones, whose properties were altogether more consistent. In vitro protein digestibility turned out to be a useful parameter in evaluating wild and improved samples.IITA (International Institute of Tropical Agriculture) fellowship recipients.     

Comparison of nutritional and antinutritional factors in soybean and fababean seeds with or without cortex

The composition and contents of nutritional factors such as proteins, lipids, carbohydrates, fibers, amino acids, and antinutritional factors such as trypsin inhibitors, phytic acid, and tannins were compared in soybean and fababean seeds with emphasis placed on the nutritional improvement of the seeds by cortex removal. Protein hydrolysis analysis for both whole seeds and seed with cortex removed revealed the presence of a large amount of lysine, arginine, aspartic acid, glutamic acid, glycine, and leucine while these seeds contained a low level of tryptophan, cystine, and methionine. Some antinutritional factors such as trypsin inhibitors, phytic acid, and tannins were detected in soybean and fababean seeds: phytic acid content and trypsin inhibitor activity were higher in soybean seeds than in fababean seeds while the difference in the tannin content was less pronounced. It was found that most of the tannins occurred in the cortex of the soybean and fababean seeds. Tannins are polyphenolic compounds that readily form indigestible complexes with proteins and other macromolecules under specific environmental conditions. By removal of the cortex, tannins were almost completely eliminated without changes in the protein composition and amino acids. From these results, it is assumed that since soybean and fababean seeds contained a high concentration of antinutritional factors in the cortex such as tannins, the utilization of the legume seeds after removal of all of the cortex is suitable for human diet or industrial products.