Optimization of Goat Milk with ACE Inhibitory Peptides Fermented by Lactobacillus bulgaricus LB6 Using Response Surface Methodology

In the present study, the incubation conditions of goat milk fermented by Lactobacillus bulgaricus LB6 were optimized to increase the angiotensin converting enzyme (ACE, EC 3.4.15.1) inhibitory activity by Box–Behnken design of response surface methodology. Incubation temperature, whey powder, and calcium lactate had significant effects on ACE inhibition rate and viable counts of LB6 during incubation. The results showed that optimal conditions of fermentation were found to be 37.05 °C, 0.8% (w/w) whey powder and 0.50% (w/w) calcium lactate. ACE inhibition rate increased significantly from 71.04 ± 0.37% to 83.31 ± 0.45% and the viable counts of Lactobacillus bulgaricus LB6 reached to 8.03 × 10(7) cfu·mL(−1) under the optimal conditions, which approached the predicted values 83.25% and 8.04 × 10(7) cfu·mL(−1). The optimal fermentation conditions can be a good reference for preparing ACE inhibitory peptides from goat milk.