Effects of bioprocessed antinutritional factors on bean protein quality : with special emphasis on Phaseolus vulgaris L.

Legumes, e.g. beans and peas, can contain antinutritional factors. Some varieties of faba beans (Vicia faba), soya beans (Glycine max ) and white kidney beans (Phaseolus vulgaris) can contain in their raw state antinutritional factors such as tannins, trypsin inhibitors and lectins respectively which negatively effect the protein digestibility by nonruminants e.g. pigs. Also the storage protein is not easily digested by nonruminants. The main aim of the present study was to find a reasonable alternative for the technological elimination of antinutritional factors and cleavage of storage proteins in beans to increase the protein digestibility in pigs. Germination experiments with soya- and white kidney beans resulted in a decrease of the amount of trypsin inhibitors and lectins respectively but the amount of tannins remained constant during germination of faba beans. When these three germinated legume varieties were used for in vitro protein digestibility experiments with pepsin and pancreatin results indicated an increased protein digestibility in all the three legumes, Further research on white kidney beans resulted in the isolation of an enzyme extract from germinated beans, capable of cleaving lectins; and phaseolin, a storage protein. After investigations it appeared that also specific proteases and glycosidases from microbial organisms, other plants and animals were able to cleave lectin and/or phaseolin into smaller fragments. Germination increased the deviation of the amino acid composition of faba-, soya- and white kidney beans from what is ideally needed for feeding of pigs. Feeding germinated white kidney beans to pigs as compared to ungerminated beans improved the digestion of the bean protein by a decrease of the antinutritional factors and an increase in true ileal bean protein digestibility.