Insights into the non-targeted metabolomic profile, rheological, functional and structural characteristics of rice bran and pulse protein isolates

Abstract

Rice bran protein isolates and seven legume protein isolates (moong bean, green pea, white pea, black chickpea and white chickpea, soya bean and lentil) were evaluated for functional, structural and metabolomic properties. Rice bran protein isolates (RBI) had higher solubility, foaming, oil absorption capacity and water absorption capacity but lower denaturing temperature compared to legume proteins. The functionality of proteins isolates impacted significantly with structural characteristics. The β-sheet, α-helix, β-turn and anti-parallel β-sheets proportions were evaluated by FTIR. RBI revealed lower molecular weight, less rigid conformational structure and lower proportion of β-sheet. The evaluation of untargeted metabolomics compounds was determined by ultraperformance liquid chromatography quadruple time-of-flight ion mobility mass spectrometry (UHPLC-QTOF-IMS), evaluated using PCA and presented as a heatmap. Analysis revealed 46 metabolites including sugars, amino acids, lipids, terpenoid, phenolics, saponins and their derivatives. Significant differences in selected compounds from 126 identified metabolites among protein isolates were observed. This work provides new insights into metabolite distribution among protein isolates and also presents future implementations for applications in food and nutraceuticals.