Optimization of tocols and γ-oryzanol extraction from rice bran using ultrasound and soybean oil as a green solvent

Abstract

A new process was developed to extract tocols and γ-oryzanol from rice bran using ultrasound with soybean oil as a natural solvent. Results were compared to the conventional solvent method. The extraction process was optimized using response surface methodology (RSM) with three independent process variables as amplitude level (A) (20-60%), extraction temperature (B) (25-65°C) and time (C) (20-60 mins). Statistical analysis indicated that models developed for all responses were significant. Linear terms of all process variables had significant effects on α-tocopherol, γ-tocopherol, and γ-oryzanol, while quadratic effects of amplitude level (A2), temperature (B2) and time (C2) on all responses were highly significant. Optimal process conditions for maximum yield of tocopherols and γ-oryzanol were 40% amplitude level, 65°C solution temperature and 40 mins. Yields of α-tocopherol and γ-oryzanol in oil extracted under the optimal conditions or ultrasound-assisted soybean oil extraction (O-UASO) were comparable to oil yield produced by conventional solvent extraction (O-CSE). Interestingly, O-UASO showed higher total antioxidant activities compared with O-CSE. Extraction using ultrasound with soybean oil was proposed as an effective alternative green process to improve oil functionality without the need for separating environmentally hazardous organic solvents.