Effects of NaCl curing and subsequent fermentation with Lactobacillus sakei or Lactobacillus plantarum on protein hydrolysis and oxidation in yak jerky

The impacts of added NaCl and subsequent fermentation with Lactobacillus sakei or Lactobacillus plantarum on proteolysis and protein oxidation in yak jerky were investigated. The proteolytic activity, peptide content and free amino acid concentration displayed decline patterns as NaCl content increased from 0 to 4% (P < 0.05), while the salted jerky fermented with lactobacillus demonstrated higher proteolysis profiles than the control without starter cultures (P < 0.05), and jerky fermented with Lactobacillus sakei showed the highest proteolysis. Adding NaCl promoted protein carbonylation, sulfhydryl loss and tryptophan fluorescence quenching. Fermentation with lactobacillus, especially with Lactobacillus sakei, effectively reduced the oxidation of sarcoplasmic and myofibrillar proteins in salted jerky (P < 0.05). Electrophoretogram showed that the changes in number and intensity of protein bands were from combined action of NaCl curing and microbial fermentation. The results suggest that both of NaCl addition and subsequent fermentation influence the protein chemical properties and hence modify the relevant quality traits of yak jerky.