Studies on time-related changes of dipeptidyl peptidase during processing of Jinhua ham using response surface...

Sixty experimental Jinhua hams were processed by traditional methods using green hams from local cross-bred pigs of Lanxi, Zhejiang province, PR China. Biceps femoris was sampled from five hams randomly taken after each processing stage. Potential activities of DPP I and IV in addition to the changes of some enzyme influencing factors were determined. The effects of temperature, sodium chloride content, sodium nitrate content and pH value on the activities of muscle DPP I and IV were evaluated using Response Surface Methodology (RSM) and the actual activities of muscle DPP I and IV during Jinhua ham processing were estimated. The results showed that potential activity of muscle DPP I decreased gradually from 8608.23 to 1842.06 Ug(-1) before loft-aging and then increased gradually from 1842.06 to 12196.60 Ug(-1) at the end, while that of muscle DPP IV decreased continuously and about 11% of the initial potential activity was left at the end of processing. Most of the chemical components analyzed in Biceps femoris as well as physical parameters changed greatly during processing. Temperature, sodium chloride concentration and pH value influenced DPP I and IV activities significantly. However, nitrate concentration from 0 to 50 mgkg(-1) showed little effect. By regression analysis, two quadratic regression equation models were built. The models showed that DPP I could have strong activity during Jinhua ham processing, whereas the activity of DPP IV was always very weak despite its strong potential for activity. In conclusion, muscle DPP I may be a key enzyme responsible for the generation of dipeptides in Jinhua ham processing while the effect of DPP IV was possibly very limited.