This study attempted to investigate the effects of reducing sodium content and adding Lactobacillus paracasei M3, with high angiotensin-converting enzyme (ACE) inhibitory activity in skimmed milk, as an adjunct starter culture on the physicochemical properties and in vitro antihypertensive potential of Cheddar cheese. One control group (100% NaCl) and three experimental groups, 50% NaCl + 50% KCl, 100% NaCl + 0.5% L. paracasei M3, and 50% NaCl + 50% KCl + 0.5% L. paracasei M3 were set up. The major chemical components, microbial load, proteolysis, texture, flavor and ACE inhibitory activity of these four groups were evaluated. The results showed that there was no significant difference in the principal chemical components among the four groups (P > 0.05). The number of lactic acid bacteria, pH 4.6 soluble nitrogen and total free amino acid content were significantly higher in the experimental groups than the control group (P < 0.05), while hardness and pH were lower in the experimental groups (P < 0.05) and bitterness was higher. The inhibition percentages of the three experimental groups toward ACE were 65.2%, 74.3% and 78.7% after six months of ripening, which were 19.6%, 36.2% and 44.4% higher than that of the control group, respectively. We concluded that potassium salt substitution and use of L. paracasei could contribute to the production of ACE inhibitory peptides with antihypertensive potential in cheese, but further research is needed to understand their effect on the flavor of cheese.

Malatya cheeses with different cow to goat milk ratios (1:0, 3:1, 1:1, 1:3 and 0:1) were prepared to investigate the effect of blend ratio between cow and goat milk on the yield, physicochemical properties, texture, color, melting temperature, sensory quality, protein hydrolysis and antioxidant properties of traditional Malatya cheese during the ripening process. The results showed that increasing the proportion of cow milk resulted in lower protein content, hardness, chewiness, brightness and whiteness values, and higher moisture content of Malatya cheese. As the ripening time increased, the degree of proteolysis gradually increased, and the antioxidant activity of cheese gradually increased until the 60th day, and then decreased. There was no significant difference in cheese yield between the 50% cow milk addition and the pure goat milk groups (P > 0.05), while the former had the highest sensory evaluation score. Malatya cheese prepared from 50% cow milk and 50% goat milk showed no significant difference in the degree of proteolysis compared with pure goat milk cheese, and in 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity, superoxide anion radical scavenging capacity, reducing power, or total antioxidant capacity compared with traditional Malatya cheese (P > 0.05). From these results, it was found that the optimal addition level of cow milk in Malatya cheese was 50%, which imparted good quality and antioxidant properties to Malatya cheese.