The purpose of this research was to screen out the optimal -producing peptide conditions for cow milk fermented by Lactobacillus bulgaricus LB6. The effects of temperature, inoculation size, time and skim milk concentration on the ACE inhibition rate of fermented milk were investigated by single factor experiment, and the optimal fermentation conditions were determined by orthogonal experiment. The conditions of the single factor experiment were: Temperatures were 37° C, 39° C, 42° C, 44° C and 46° C. The inoculation amount was 1%, 3%, 5%, 7% and 9%, the time was 8h and 10h. At 12h, 14h and 16h, the concentration of skim milk was 8%, 10%, 12%, 14% and 16%, respectively. The results showed that the optimal fermentation conditions for ACE inhibitory peptide produced by Lactobacillus bulgaricus LB6 were 4% inoculation, 13h in time, 42°C in temperature and 13% in skim milk. Under this condition, the ACE inhibition rate reached 76.50% and the OD value was 0.330. The titration acidity was 116.4°T, the pH was 4.62, and the sensory evaluation was 75 scores.
Prebiotics can play an important role in functional foods. In this paper, casein and five probiotics were selected to study the effects on ACE inhibitory peptides in fermented milk of L. bulgaricus LB6 through Plackett-Burman design, so as to improve the production of ACE inhibitory peptides. The results showed that xylooligosaccharides (XOS), fructosaccharide (FOS) and inulin had the most significant effect on the yield of ACE inhibitory peptides. Optimization added the amount of the three prebiotics added, that is, the amount of XOS added was 0.7%, the amount of FOS added was 1.1%, and the amount of inulin added was 0.7%. It provides a basis for subsequent optimization experiments.
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