Effect of okara and biovalorised okara consumption on postprandial amino acid response: a crossover randomised controlled trial

Abstract

Okara is a protein-rich food by-product that can be biovalorised with Rhizopus oligosporus to improve its protein digestibility and quality. This study investigated postprandial circulating amino acid changes following okara and biovalorised okara biscuits consumption in middle-aged and older Singaporean adults. Participants of the crossover study (n = 15) undertook 3 separate 2-h meal tolerance test with 100 g of control biscuits (C), biovalorised okara biscuits (RO), and autoclaved okara biscuits (AOK). The same recipe was applied across all biscuits, but with 20% wheat flour substitution for RO and AOK with the respective okara. Total and free amino acids of the biscuits and circulating free amino acids of the participants were analysed by cation-exchange chromatography. Incremental area under curve (iAUC) and peak concentrations of amino acids were assessed, with results presented as mean [95% confidence interval]. While total biscuit amino acid content showed significantly greater quantities for RO and AOK compared to C, free amino acid content (nmol/g) was in the order of C < AOK < RO. Amino acid iAUC had no significant difference, as demonstrated with total amino acids iAUC (μmol/L·min) (P = 0.568, C: 23649 [13738, 33560], RO: 23284 [13374, 33195] & AOK: 17257 [7346, 27168]). Amino acid digestion and absorption did not differ between okara-containing and control biscuits at the levels consumed in this study, potentiating the need for higher protein dosages, larger sample sizes, and longer trial durations for detecting discernable improvements. This trial was registered under www.clinicaltrial.gov (NCT03978104, 25 May 2019).