Postprandial Glycemic, Insulinemic, and Short-Chain Fatty Acids Responses Following the Consumption of Okara and Biovalorized Okara Incorporated Biscuits

Abstract

Abstract Objectives Okara is a fiber-rich food processing by-product. However, it is underutilized as food due to its rapid putrefaction and poor sensorial properties. Valorization via fermentation (biovalorization) can alleviate its undesirable qualities while augmenting its soluble fiber content. The increase in soluble fiber may improve postprandial glycemic and insulinemic responses, potentially via generation of short-chain fatty acids (SCFAs) from colonic bacteria fermentation. This study aimed to assess the effect of consuming okara and biovalorized okara-containing biscuits on postprandial glucose, insulin and SCFAs responses in older Singaporeans. Methods Fifteen healthy middle-aged and older Singaporeans participated in a randomized controlled crossover trial. Subjects underwent a 4-hour mixed meal tolerance test with 100 g ingestion of 3 types of biscuits – control (C, no okara), biovalorised okara (RO) and autoclaved okara (AOK). RO and AOK biscuits were produced by 20% substitution of wheat flour with okara powder that was fermented with Rhizopus oligosporus (7% w/w) or autoclaved. The 4-hour incremental area under the curve (iAUC) of glucose, insulin and SCFAs (acetate, propionate and butyrate) were assessed. β-cell function was evaluated based on glucose stimulated insulin secretion, using a ratio of 4-hour AUC of insulin to glucose. Estimated insulin sensitivity (ISI) and metabolic clearance rate (MCR) were assessed with Stumvoll Index. Results Although no difference in glucose response was noted, RO showed significantly lower insulin iAUC (RO: 8931 ± 1058 mU/L × min, mean ± SE; C: 10271 ± 866 mU/L × min, p = 0.021) and improved β-cell function (p = 0.028) compared to C. AOK yielded significantly greater ISI and MCR compared to C (pISI = 0.016, pMCR = 0.009) while RO showed no difference against AOK or C. Significantly higher acetate and total SCFAs iAUC were evident for both RO and AOK relative to C (C vs RO: pacetate = 0.012, ptotal SCFA = 0.001; C vs AOK: pacetate = 0.015, ptotal SCFA = 0.001). AOK also had significantly greater propionate and butyrate iAUC compared to C (C vs AOK: pacetate = 0.002, pbutyrate = 0.001). Conclusions Consumption of okara and biovalorized okara-containing biscuits offers the benefit of attenuating postprandial insulinemic response possibly via SCFAs modulation. Funding Sources Singapore Ministry of Education