Label-free proteomics reveals the mechanism of bitterness and adhesiveness in Jinhua ham.

To obtain better understanding of the formation mechanisms of bitterness and adhesiveness, protease activities, proteolysis index and protein degradation were investigated among raw, normal and defective hams. Normal and defective hams both showed a decrease in cathepsin B and B + L activities compared with raw ham, while higher residual activities were observed in defective ham. Approximate 1.2-fold values of proteolysis index were observed in defective ham than in normal ham, indicating that cathepsin B and B + L activities were key contributors in degrading muscle proteins of dry-cured ham. 322 proteins were identified by label-free proteomics, and 49 down-regulated proteins were found in the comparison between normal and defective hams. Creatine kinase, myosin, α-actinin and troponin-T showed the most intense response to bitterness and adhesiveness of dry-cured ham, confirmed by partial least squares regression analysis. Myosin could be a suitable biomarker to monitor bitterness and adhesiveness of dry-cured ham.