Elucidation of the low resistant starch phenotype in Phaseolus vulgaris exhibited in the yellow bean Cebo Cela

Authors: HOOPER, SHARON - Michigan State University; BASSETT, AMBER - Michigan State University; SADOHARA, R - Michigan State University; Cichy, Karen

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2021
Publication Date: 8/15/2021
Citation: Hooper, S.D., Bassett, A., Sadohara, R., Cichy, K.A. 2021. Elucidation of the low resistant starch phenotype in Phaseolus vulgaris exhibited in the yellow bean Cebo Cela. Journal of Food Science. 86(9):3975-3986. https://doi.org/10.1111/1750-3841.15883.
DOI: https://doi.org/10.1111/1750-3841.15883

Interpretive Summary: Dry beans belong to the legume family and are grown for human consumption globally. Nutritionally, they are important because of the high quantities of protein, vitamins, minerals and complex carbohydrates they contain. Of these, carbohydrates comprise the main portion of dry beans, accounting for 55–65%; with starch and dietary fiber being the major components. Starch can be categorized based on its digestibility or enzymatic hydrolysis into rapidly digestible starch, slowly digestible starch, and resistant starch. Resistant starch (RS) can be defined as the portion of starch that resists digestion, passing directly through the small intestine into the colon to be fermented by gut microbes to form short fatty acids which have beneficial health effects. Studies have shown that in uncooked bean flours the RS content is generally high ranging from 32 - 38% with few exceptions. The objectives of this study were to investigate the mechanism for low RS content in select bean genotypes and compare them to beans within similar market classes and to assess the impact of low RS content on physicochemical properties of uncooked bean flours and isolated native starches. A unique yellow bean genotype, Cebo Cela with low RS content of 1.5% in raw beans was characterized. The mechanism for low RS of Cebo Cela is due to a-amylase activation of 21.9% and not amylose content or starch structure. Yellow bean starch granules were digested faster than white bean starch granules because of the lower proportions of amylopectin chains.

Technical Abstract: Dry beans (Phaseolus vulgaris) are rich in complex carbohydrates including resistant starch (RS). Resistant starch, 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 resistant starch phenotype was evaluated in whole bean flour and starch in Cebo Cela (yellow), Canario (yellow), Alpena (navy) and Samurai (otebo). Alpha 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.