Antioxidant and antihypertensive protein hydrolysates from rice bran: optimization of microwave assisted extraction

Abstract

In this study, the production of antihypertensive and antioxidant hydrolysates by microwave assisted enzymatic hydrolysis was optimized for the proteins extracted from the rice bran. The central composite design was used for optimization and the independent parameters were solid/liquid ratio, power, and time. Optimum protein extraction parameters were obtained as; 0.42 solid/liquid ratio, 100.68 W power, 100.68 s. During alcalase and pepsin hydrolysis, solid/liquid ratio and time were selected independent factors, the results of angiotensin-converting enzyme (ACE) inhibitory activity, degree of hydrolysis (DH), and DPPH radical scavenging activity were used as responses. Optimum hydrolysis parameters were determined. The DH, DPPH radical scavenging activity, ACE inhibitory activity, values were 40.60%, 36.26%, and 59.16% respectively. The rice bran protein hydrolysates was fractionated as\u2009<\u20091 kDa, 1–5 kDa, and 5–10 kDa by ultrafiltration. The highest ACE inhibition activity, DPPH, and OH radical scavenging activity and Trolox equivalent antioxidant activity values were respectively obtained for 5–10 kDa fraction as 76.66%, 13.25%, 5.03%, and 8.82 µg trolox/mg sample. The study may provide a new approach for obtaining biofunctional protein hydrolysates from rice bran emerging relatively high volumes as a by-product during paddy processing.