Dry beans(Phaseolus vulgaris) are rich in complex carbohydrates including resistant starch (RS). RS, the starch fraction that escapes digestion, typically ranges from 35% in raw beans to 4% in cooked beans. A low RS bean genotype, Cebo Cela, was identified with 96% less RS (1.5% RS) than normal raw beans. The goal of this research was to elucidate the factors responsible for this low RS phenotype. The low RS phenotype was evaluated in whole bean flour and starch in Cebo Cela (yellow), Canario (yellow), Alpena (navy) and Samurai (otebo). α-Amylase activation was found to be a major contributor of the low RS content phenotype of the whole bean flour for Cebo Cela (-21.9% inhibition). Total starch (43.6%-40.2%), amylose (31.0%-31.5%), molecular weight and chain length distributions of amylose and amylopectin did not contribute to the low RS phenotype. Yellow bean starches were digested nearly 1.5 times (95%-94%) faster than starch granules from otebo and navy beans (65%-73%) due to lower proportions of amylopectin chains. PRACTICAL APPLICATION: This study is of value to the food industry because the yellow bean, Cebo Cela, is easily hydrolyzed by α-amylase and also has α-amylase promotion properties. Therefore, Cebo Cela can be used as an alternate starch source for ethanol fermentation and for the production of maltodextrins and fructose/glucose syrups which are used as food thickeners and sweeteners.
Keywords: Resistant starch; alpha amylase; bean flour; starch structure; yellow bean.
© 2021 Institute of Food Technologists. This article has been contributed to by US Government employees and their work is in the public domain in the USA.