Fractionation of foam-mat dried rice bean hydrolysates using membrane filtration and solid phase extraction: Peptide- and phenolic-based fractions with bioactive potential

Abstract

Flavourzyme was used to hydrolyze the germinated rice bean, and the hydrolysates were separated using membrane ultrafiltration with a molecular weight (MW) cut-off of 3 kDa. The ultrafiltration permeate fraction (UFP), non-fractionated hydrolysate (RH), and ultrafiltration retentate fraction (UFR) were foam-mat dried at two temperatures, 60 and 70 °C. The content of each phenolic composition in dried RH samples decreased with increasing drying temperature particularly gallic acid, p-coumaric acid, vanillin, rutin, and, quercetin dropped by 27, 24, 21, 35 and 33%, however the kind of phenolic compositions identified in dried samples was unaffected by drying temperature. Dried UFR and dried UFP had different chromatograms. When the dried UFP and dried UFR chromatograms were examined, it was discovered that the intensity of the peaks in the dried UFR chromatogram was much lower. The majority of phenolics can pass through ultrafiltration membranes with a molecular weight cut-off of 3 kDa, according to this finding. Individual phenolic compound levels in dried UFP samples were similar to RH, implying that the majority of phenolic components in dried rice bean protein hydrolysate were smaller than 3 kDa. With increasing drying temperature, gallic acid, p-coumaric acid, catechol, epicatechin and naringenin levels in dried UFP samples were decreased. The antioxidant capacity of dried rice bean hydrolysate was discovered to be due to phenolic components (gallic acid, epicatechin, catechol, ferulic acid, and rutin), which were found to be more prevalent than peptide fractions. As a result, rice bean hydrolysates could bring novel health advantages, which could lead to the development of nutraceuticals and food products.