Protein and Sugar Extraction from Rice Bran and De-Oiled Rice Bran using Subcritical Water in a Semi-Continuous Reactor: Optimization by Response Surface Methodology

Abstract

Abstract The extraction of protein and sugar from rice bran and de-oiled rice bran using subcritical water was evaluated in a 30-ml semi-continuous reactor. The effects of the three main factors, operating temperature, time and pressure, on the total sugar and protein yields obtained were investigated using analysis of variance and response surface methodology. A central composite design was performed in order to determine the most likely optimum conditions for the extraction process for both substrates individually and together. The developed models had a very high regression coefficient (R2) value (0.94 – 0.98), and demonstrated that the three main factors investigated had a significant effect on the sugar yield, whilst only time and its interaction with temperature were significant factors controlling the extracted protein yield. Based on the response surface and contour plots, the optimum conditions were evaluated for maximal extracted sugar and protein yields, which reached 100% for protein, from the two materials.