Improving effect of enzyme hydrolysis of corn gluten meal by assistant of electron beam irradiation

Abstract: In this study, the key technology of enzymatic hydrolysis of corn protein powder and the improvement of enzyme effectiveness with the electron beam irradiation technology were researched. Corn gluten meal (mass fraction of 79.4 %) was used as raw material. Alacalase was used to hydrolyze corn gluten meal, and degree of hydrolysis (DH) and 1,1-diphenyl-2-picryl-hydrazyl (DPPH) inhibition were used as testing indexes. In order to develop and optimize conditions for the enzymatic hydrolysis reaction, we investigated three variables: enzyme solution temperature, pH value, and ratio of enzyme to substrate. One-factor-at-a-time (OFAT) and response surface metrology (RSM) experiment were used to optimize the conditions for hydrolysis. Based on the optimized results, the influences of different electron beam irradiation doses on the DH and DPPH inhibition of corn gluten meal were studied. The irradiation dose rate was 1.08 kGy/s, the irradiation time were 0, 1, 2, 3, 4, 5, and 6 seconds, the irradiation doses were 0, 1.08, 2.16, 3.24, 4.32, 5.4 and 6.48 kGy. And the microcosmic surface features of corn gluten meal in three irradiation doses (0, 3.24 and 6.48 kGy) by electron beam irradiation treatment were analyzed by scanning electron microscope (SEM). The results of OFAT showed that, the DH reached the highest value 37.89%±2.89% when the enzyme solution temperature was 60℃, and the DPPH inhibition reached the highest value 58.45%±2.07 % when the temperature was 40℃. The DH reached the highest value 40.81%±0.8% when the pH value was 9, and the DPPH inhibition reached the highest value 72.93%±0.96% when the pH value was 6. The DH reached the highest value 38.31%±0.8 % when the ratio of enzyme to substrate was 12%, and the DPPH inhibition reached the highest value 67.07%±0.83% when the ratio of enzyme to substrate was 2%. The results of RSM test showed that, the optimized parameters of enzyme hydrolysis were: enzyme solution temperature was 50℃, pH value was 8.6, ratio of enzyme to substrate was 9.13%. On these conditions, the DH value of corn gluten meal was 40.26%±0.23%, and the DPPH inhibition of corn antioxidative peptides (CPS) was 70.74%±0.41%. In the electron beam irradiation experiment, the optimize irradiation dose was 3.24 kGy, with the DH of 49.17%±0.42% and DPPH inhibition of 73.03%± 1.02%. The SEM results showed that compared with the blank sample, the smoothness of corn gluten meal powder with irradiation decreased, and the specific surface area was increased. The results provide a reference for corn processing industry and also for further studies on corn antioxidant peptides.