Abstract:

The microwave-assisted enzymatic hydrolysis of Pinctada martensii muscle proteins was optimized by response
surface methodology. Alcalase 2.4L was chosen as the best enzyme to hydrolyze Pinctada martensii muscle proteins based
on free ammonia nitrogen content and DPPH radical scavenging activity of hydrolsates. The levels of operating parameters
such as substrate concentration, E/S ratio, solvent temperature, microwave power, radiation time and water bath heating
time were established by single-factor experiments for response surface Box-Behnken design. Based on the mathematical
product of degree of hydrolysis (DH) and DPPH radical scavenging rate, the optimal hydrolysis conditions were determined
as a solvent temperature of 58 ℃, microwave treatment at 300 W for 17 min after addition of 5 000 U/g Alcalase 2.4L, and
subsequent water bath heating at 58 ℃ for 1.5 h. Under these conditions, the maximum predicted DH was 26.15%, which
was multiplied by DPPH radical scavenging rate to obtain 0.224 4. The small difference from the actual values observed in
verification experiments suggested a high degree of fitting.

Key words: Pinctada martensii muscle proteins, microwave-assisted enzymolysis, antioxidant activity, response surface methodology