Extraction solvents affecting phytochemicals in food colorant prepared from purple glutinous rice bran

Abstract

This study investigated the effect of extraction solvents on the concentrations of bioactive compounds in the colorant obtained from purple rice bran. Ten different solvents including 100% water (W), 100% W–HCl 95%, ethanol (EOH), 95% EOH–HCl, 50% EOH, 50% EOH–HCl, 95% methanol (MeOH), 95% MeOH–HCl, 50% MeOH, and 50% MeOH–HCl were used to extract the rice bran. Results indicated that the solvents had a significant effect on the concentrations of the bioactive compounds and visual color in the colorant. The 50% EOH–HCl and 50% MeOH–HCl showed the highest levels of cyanidin-3-O-glucoside, cyanidin-3-O-rutinoside, delphinidin, cyanidin, pelargonidin, and malvidin, total anthocyanins, (+)-catechin, caffeic, p-coumaric, ferulic, and total phenolic acids, whereas the highest level of gallic acid was observed when extracted using 50% EOH and 50% MeOH. The highest concentrations of the tocols, γ-oryzanol, zeaxanthin, lutein, and β-carotene were observed in the colorant extracted by 95% EOH. This suggests that aqueous alcohol with a small amount of HCl (0.1 N) was an effective solvent for extraction of purple rice bran and preparation of colorant containing high important compounds. This solvent has potential as an alternative bio-solvent for green extraction of functional colorants.