Environmentally friendly recovery of proteins and phenolic compounds from defatted rice bran

The study aimed to evaluate the efficiency of enzymatic pretreatment, ultrasonic probe-treatment and combined enzymatic pretreatment and treatment ultrasonic probe-treatment on recovery proteins and phenolic compounds from defatted rice bran (DRB). Their effects on protein solubility and phenolic profile were also evaluated. The protein sources were DRB and enzymatically hydrolyzed defatted rice bran (HDRB), from a cellulolytic enzyme complex. Experimental parameters for producing hydrolyzed rice bran from cellulolytic enzyme treatment and protein concentrates were standardized using central composite rotational designs (CCRDs), in which the combinations of independent variables were assessed, and dependent variables reducing sugars, soluble protein, and protein yield were evaluated. The concentrate from enzymatically hydrolyzed DRB followed by ultrasonic probe treatment (HDRBC-U, 441 W, 10 min) showed the highest protein yield (43.7 %), followed by the concentrate obtained from enzymatic hydrolysis of DRB assisted by ultrasonic probe (DRBC-EU, 32.1 %). Both yields were significantly higher compared with the concentrate from DRB under orbital stirring (DRBC, 5.4 %). Protein concentrates had changed its solubility profiles, with increases in albumin (90 %) and globulin (79 %), maintenance of prolamin, and a marked increase in the glutelin fraction (236 %) by comparison to DRB. In addition, phenolic compounds, particularly ferulic and p-coumaric acids, were increased, with DRBC-EU displaying the highest phenolic content (1593 μg GAE g^-1). The results showed that integrated green strategy enhances protein recovery efficiency while simultaneously increasing phenolic content of concentrate, thereby improving the potential of rice bran protein concentrates for application to develop of protein- and phenolic-enriched food products.