Value-added products from rice bran and soybean by hydrolysis in subcritical water

Abstract

This study deals with the production of new value-added product derived from agricultural by-products which are raw and deoiled rice bran as well as raw and deoiled soybean meal by means of subcritical water (SW) bydrolysis. The SW hydrolysis reaction was carried out in a closed bath reactor in which the effect of temperature in the range of 200-220 ํC, reaction time of 10-30 min, raw material to water weight ratio of 1:5 and 2:5, were determined on the yields of protein, amino acid, and reducing sugars. The hydrolysis products were separated into solid residue, whose dried weight was measured, and the aqueous product, which was analyzed for proteins, amino acids, reducing sugar and its antioxidant activity. The results in the present study suggested that subcritical water could be used to potentially hydrolyze raw and deoiled rice bran and raw and deoiled soybean meal into more valuable products. The suitable hydrolysis time was 30 min the proper weight ratio of the raw material to water was 1:5. The reaction temperature that was suitable for the production of protein and amino acids was 220 ํC for raw and deoiled rice bran, 210 ํC for raw soybean meal, and 200 ํC for deoiled soybean meal. The products were also found to have antioxidant activity as tested by ABTS scavenging assay. In addition, the hydrolysis product of deoiled rice bran obtained at 200 ํC after 30 min and ratio of 1:5 was demonstrated for potential use as nutrients for yeast growth. As a test of possible application of the product in human food, sensory evaluation was conducted on the deoiled rice hydrolysis product, in which two pairs of test products were compared: the milk control and the milk added with rice bran product, and the coffee control and the coffee added with the rice bran product. The analysis of the results showed that the number of testers who preferred the milk added with rice bran product was significantly higher than those preferring the milk control (P <= 0.05) and the number of the testers preferring of the coffee control and the coffee added with extraction product were not significantly different (P > 0.05). From the results of this study, it was concluded that SW hydrolysis is an interesting technique that could be used to develop new value-added functional foods from low cost agricultural by-products.