Influence of enzyme type and hydrolysis duration on the metabolite profiles of red sorghum (Sorghum bicolor L.): Untargeted metabolomic combined with chemometrics approach

Abstract

Red sorghum (Sorghum bicolor L. Moench) is a nutrient-rich cereal containing starch, proteins, lipids, non-starch polysaccharides, and health-promoting antioxidant phenolics. This study investigated the influence of enzyme type and hydrolysis duration on the metabolite profiles of sorghum hydrolysates to identify key bioactive constituents and determine optimal hydrolysis conditions.Hydrolysis was conducted using bromelain and papain at 60 °C, pH 7.6, across five time points (0–4 h), with an enzyme-to-substrate ratio of 1:10 (w/w). Metabolomic profiling was performed via High-Performance Liquid Chromatography-Orbitrap High-Resolution Mass Spectrometer (HPLC-Orbitrap-HRMS). Chemometric techniques, including Principal Component Analysis (PCA), partial least square-discriminant analysis (PLS-DA) and variable importance in projection (VIP) scoring, were applied to evaluate treatment effects on metabolite variations. Chemometric analysis revealed enzyme- and time-dependent alterations in red sorghum metabolites, with bromelain promoting greater diversity, particularly enriched in amino acids (L-phenylalanine), dipeptides (Leu-Leu), and flavonoids (taxifolin), especially with prolonged incubation. Chemometrics analyses demonstrated distinct metabolite patterns influenced by enzyme type and hydrolysis time, with amino acids serving as key discriminants.

These findings underscore the critical role of enzyme selection and incubation period in enhancing the functional profile of sorghum hydrolysates, positioning bromelain as a promising enzyme for generating bioactive-rich extracts.