EFFECTS OF DIETARY FIBER AND TANNINS ON PROTEIN-UTILIZATION IN DRY BEANS (PHASEOLUS-VULGARIS)

The nutritional value of dry bean (Phaseolus vulgaris) protein is typi cally lower than that of cereal and animal proteins, but the factors r esponsible for the low nutritional value of bean protein have not been clearly identified. In this study, the ability of dietary fiber and t annins to lower protein utilization in dry beans was investigated usin g weanling rats. The rats were fed eight experimental diets containing varying amounts of bean dietary fiber and tannins. Both protein diges tibility and net protein ratio (NPR) were determined as measures of pr otein nutritional value. Soluble dietary fiber significantly increased fecal nitrogen losses (P less than or equal to 0.001) and reduced pro tein digestibility (P less than or equal to 0.001), while insoluble di etary fiber and tannins had no effect on either fecal nitrogen loss or protein digestibility. However, neither soluble nor insoluble dietary fiber had a significant effect on NPR, but tannins significantly redu ced NPR values (P less than or equal to 0.01). Both dietary fiber and tannins appear to contribute to the low nutritional value that is typi cal of bean protein, with soluble dietary fiber being primarily respon sible for the reduction in protein digestibility that is commonly asso ciated with dietary fiber in foods. Copyright (C) 1996 Canadian Instit ute of Food Science and Technology. Published by Elsevier Science Ltd