Time-related changes in cathepsin B and L activities during processing of Jinhua ham as a function of pH, salt and temperature

Sixty experimental Jinhua hams were processed by traditional methods using green hams from local crossbred pigs of Lanxi, Zhejiang province, PR China. Biceps femoris was sampled from five hams randomly taken after each processing stage. Potential activities of cathepsin B and L were determined. The effects of temperature, salt content, pH value and nitrate content on the activities of cathepsin B and L were evaluated using response surface methodology (RSM) and the actual activities of cathepsin B and L during Jinhua ham processing were calculated. The results showed that potential activities of cathepsin B and L decreased gradually from 11332.05 to 9955.50 U g−1 prior salting to 1055.32–1359.90 U g−1 at the end of post-aging, respectively. After processing, about 9.31% original potential activity of cathepsin B and 13.66% original potential activity of cathepsin L were left. Temperature, pH value and salt content showed significant effects on cathepsin B and L activities. By stepwise regression analysis, two quadratic regression equation models were built individually for estimating cathepsin B and L activities. The models predicted that the actual activities of cathepsin B and L were less than 5% of their corresponding potential activities most of the time before half of loft-aging and about 15% and 20% during the rest processing periods. Nevertheless, cathepsin B and L retained actual activities throughout processing, especially during loft-aging and post-aging periods.