Abstract:

The conditions for ultrasonic-assisted extraction of protein from Guangchang while lotus seed were optimized
by single factor experiments and response surface methodology. The extracted proteins were hydrolyzed using alcalase and
pepsi singly or in sequential combinations, and antioxidant activities of the resulting hydrolysates were analyzed. The results
suggested that the optimum conditions under a fixed ultrasonic power of 250 W for extracting protein from Guangchang
white lotus seed were determined as follows: solid/solvent ratio, 1:14; extraction temperature, 35.5 ℃; extraction time,
58 min; and NaCl concentration, 0.14 mol/L. Under these conditions, the extraction yield of protein was 89.86%. Sodium
dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that molecular weights of the extracted
proteins were mainly in the range of 14–25 kD and 35–60 kD. Different treatments with pepsin and/or alcalase significantly
influenced the effectiveness of enzymatic hydrolysis of lotus seed protein and antioxidant activities of hydrolysates, and
sequential treatment with pepsin followed by alcalase was the best one. Under this treatment, the degree of hydrolysis
was 20%, and the total reduce power (A700 nm), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (IC50)
and hydroxyl radical scavenging activity (IC50) of the hydrolysate (P-A)H were 1.002, 0.379 mg/mL and 1.093 mg/mL,
respectively, demonstrating that the enzymatic hydrolysate had potent antioxidant activity.

Key words: Guangchang white lotus, extraction, enzymatic hydrolysis, antioxidant activity