Green recovery of phenolic compounds from rice byproduct (rice bran) using glycerol based on viscosity, conductivity and density

Abstract

Summary Rice bran, the industry byproduct, contains high levels of phenolic compounds. Based on glycerol, a green recovery of phenolics from rice bran was proposed. Extraction temperature ( X 1 ), glycerol concentration ( X 2 ) and liquid‐to‐solid ratio ( X 3 ) were optimised by response surface methodology. Basic physical properties, that is, viscosity, conductivity, density were analysed and UPLC ‐Triple‐ TOF / MS method was applied for phenolic identification. Results showed the optimum conditions were X 1 = 66.76 °C, X 2 = 19.47% and X 3 = 32.92 mL g −1 . Under these conditions, the recovery yield in total polyphenols was 708.58 ± 12.36 mg GAE /100 g DW . Moreover, the recovery capacity of phenolic compounds was significantly correlated with viscosity, conductivity and density of glycerol solution. Under the optimal conditions, totals of thirteen phenolic compounds were identified and phenolic acids (4‐hydroxybenzoic acid, vanillic acid, syringic acid, 4‐coumaric acid, ferulic acid and salicylic acid) were quantified. These results demonstrate glycerol can serve as an ideal green solvent to recover phenolic compounds from rice bran.