In order to reduce the sodium content of dry-cured pork coppa, partial replacement of other chloride salts was applied. The effect of different replacement schemes on the regulation of endogenous enzymes and texture quality of dry-cured pork coppa was investigated by evaluating the physicochemical properties, protein degradation, free amino acids composition, endogenous protease activity, and texture characteristics during the manufacturing process. The results showed that arginine aminopeptidase activity, leucine aminopeptidase activity, proteolysis, and springiness increased in the 75% NaCl + 15% KCl + 5% CaCl₂ + 5% MgCl₂ group as compared to the control group (100% (m/m) NaCl). The water activity decreased, and proteolysis, taste amino acid content, leucine aminopeptidase activity, dipeptidyl peptidase Ⅰ, and dipeptidyl peptidase Ⅳ activities increased in the 75% NaCl + 15% KCl + 5% CaCl₂ + 5% ZnCl₂ group relative to the control group. The 75% NaCl + 15% KCl + 5% MgCl₂ + 5% ZnCl₂ group showed enhanced proteolysis, augmented activities of alanine aminopeptidase, arginine aminopeptidase, leucine aminopeptidase, and dipeptidyl peptidase Ⅰ, and reduced product hardness. The above results indicated that partial replacement of NaCl with the selected combinations of KCl, CaCl₂, MgCl₂, and ZnCl₂ reduces the sodium content of dry-cured pork coppa while guaranteeing product quality.

An electronic nose, gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O) were used to explore the changes of aroma compounds in vinegar prepared with Monascus-fermented rice during its acetic acid fermentation process. Different multivariate statistical analysis, such as cluster analysis, principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were used to investigate the differences in volatile compounds between different stages of fermentation and to identify the characteristic volatile components. The results showed that the electronic nose could clearly discriminate samples from different acetic acid fermentation stages. A total of 54 volatile compounds were identified by GC-MS and GC-O during the acetic acid fermentation process. The characteristic aroma components were n-octanol, isobutanol and ethyl valerate for the early stage; benzoic acid, ethyl palmitate, n-hexanol, 2,4-di-tert-butylphenol and ethyl lactate for the middle stage; propyl acetate, ethyl lactate and isobutyl acetate for the mid-tolate stage; L(+)-2,3-butanediol and ethyl heptanate for the late stage. The results of this study provide a theoretical basis for aroma regulation and flavor improvement of vinegar prepared with Monascus-fermented rice.