Abstract: Sixty experimental Jinhua hams were processed according to typically traditional processing technology with fresh hams from hind legs of local hybrid pigs of Lanxi, Zhejiang Province, China. Biceps femoris was sampled from 5 hams randomly taken each time from one of the 6 processing stage, namely, green ham before salting, end of salting, end of sun-drying, mid-aging, end of aging and end of post-aging. Sample potential DPPⅣ activity at pH 7.0 and temperature 37℃ as well as some general physical and chemical indices were determined. The effects of temperature, sodium chloride content, sodium nitrate content and pH value on muscle DPPⅣ activity were evaluated with Response Surface Method by Design-experts 6.0 software, and muscle actual DPPⅣ activity after each processing stage of Jinhua ham was predicted with response surface regression equation. The results showed that during Jinhua ham processing, processing temperature, biceps femoris pH value and sodium chloride content increased gradually while biceps femoris potential DPPⅣ activity decreased gradually. The actual DPPⅣ activity was significantly influenced by processing temperature, muscle pH value and sodium chloride content (P < 0.05). Though muscle DPPⅣ could keep rather high potential activity during Jinhua ham processing, its actual activity was always very low and only 3.12% of the potential activity could be expressed at most, which therefore indicated that DPPⅣ's role in the formation of Jinhua ham flavor was quite possibly limited.

Key words: Jinhua ham, Dipeptidyl peptidase, Dipeptidyl peptidaseⅣ, Response surface