Optimization of the biological processing of rice dregs into nutritional peptides with the aid of trypsin

A protein hydrolysate was prepared from rice dregs (RD) using trypsin as a suitable protease. The hydrolysis conditions were optimized with response surface methodology, and then a mathematical model was developed to demonstrate the effect of each process parameter on the degree of hydrolysis (DH) and recovery of protein (RP). A hydrolysate with relatively high RP (75.81%) and low DH (6.95) was obtained from RD by hydrolyzing for 2.4 h at pH 7.6 52.8°C with a enzyme/RD ratio of 0.89:1000 (w/w) and RD/water level of 0.22 g/mL. The dried hydrolysate was low molecular weight peptides (predominantly <1,000 Da) and it possessed good solubility at various pH levels. Result of amino acid analysis revealed that the hydrolysate was considerably enriched in essential amino acids. Thus, the protein hydrolysate has a potential to be an excellent protein ingredient as a balanced milk replacer.