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.

The synergetic effect of nisin and high-pressure carbon dioxide (HPCD) on structural changes and leakage of nucleic acid, soluble proteins, Mg²⁺, Ca²⁺, K⁺, and dipicolinic acid from Bacillus subtilis spores was studied. Both HPCD and nisin auxiliary were used to inactivate the B. subtilis spores. The death rate of spores treated by HPCD combined with the nisin were significantly higher than HPCD alone (P < 0.05). The main cause of spore’s death is the leakage of components caused by the change of spore permeability and structural damage. The HPCD treatment damaged the spore ultrastructure, resulting in the leakage of nucleic acid, Mg²⁺, Ca²⁺, K⁺, and dipicolinic acid from spores, while nisin auxiliary to HPCD treatment damaged spore membrane, which led to spore death and play a synergetic effect. This study evaluated synergetic effects of HPCD combined with the bacteriocin nisin. The investigation provided evidence for potentially combined application of HPCD and nisin to help ensure food safe in the industry.