Study on the roles of microorganisms and endogenous enzymes in the evolution of metabolic characteristics of lean portion during traditional Chinese bacon processing

This study revealed the roles of microorganisms and endogenous enzymes in evolution of the metabolic characteristics of the lean portion of traditional Chinese bacon by exploring the changes in microbial succession, metabolic characteristics, lipid oxidation, lipid hydrolysis, lipoxygenase activity, lipohydrolase activity, protein degradation, and environmental factors during processing. The results showed that Proteobacteria and Firmicutes were the dominant phyla in the lean portion of traditional Chinese bacon, and 16 core genera (relative abundance > 1 %) were identified at the genus level. Significant differences were observed in the metabolic characteristics of different samples. A total of 23 differential metabolites were identified in positive and negative ion modes (P < 0.05, variable importance in the projection > 1.5). Peroxide value (POV), thiobarbituric acid reactive substances value (TBARS), proteolysis index (PI) and the degree of lipid hydrolysis increased during the processing. Phospholipids were the main hydrolysis substrates. Lipoxygenase activity increased first and then decreased, while lipohydrolase activity decreased gradually. The results of canonical correspondence analysis indicated that the salt content was the main environmental factor affecting the microbial composition. The results of Spearman correlation analysis and comprehensive discussion showed that the metabolic characteristics of the lean portion of traditional Chinese bacon during the curing period were mainly due to the catalysis of the endogenous enzymes in meat and the extracellular enzymes secreted by bacteria such as Brochothix, Acinetobacter, Psychrobacter, etc. The extracellular enzymes secreted by Salinivibrio, Vibrio, and Staphylococcus in light-fermented meat and final meat might have important contributions to the metabolic characteristics.