Optimization of High-yield ACE Inhibitory Peptide Fermented Milk by Response Surface Methodology and Its Texture and Flavor Characteristics

For the sake of producing fermented milk enriched in Angiotensin-I converting enzyme (ACE) inhibitory peptides, the fermented milk was fortified with sodium caseinate and a high ACE inhibitory peptide producing strain Lb. plantarum M11. The factors of sodium caseinate addition amount, inoculation amount, and fermentation temperature were selected for investigation. Aside from that, a three-factor, three-level response surface experiment was conducted on the basis of single-factor experiments to obtain the optimal process conditions for producing ACE inhibitory peptide-enriched fermented milk, as well as to probe deep into the effects of sodium caseinate and Lb. plantarum M11 on the texture and flavor characteristics of the fermented milk. As demonstrated by the results, the highest ACE inhibitory activity of the fermented milk was 83.15% when the condition was set as a sodium caseinate addition amount of 2%, inoculation amount of 1.5×10⁷ CFU/mL, and fermentation temperature of 40 ℃. The addition of Lb. plantarum M11 and sodium caseinate strikingly heightened the hardness, consistency, cohesiveness, and viscosity index of the fermented milk (P<0.05), resulting in better texture characteristics. As illustrated by the electronic tongue analysis results, the addition of Lb. plantarum M11 enhanced the acidity and richness of the fermented milk, and neither Lb. plantarum M11 nor sodium caseinate had a significant impact on saltiness, bitterness, astringency, astringent aftertaste, bitter aftertaste, or umami. This study provides a theoretical basis for the development of functional fermented milk with antihypertensive activity.