肌肉非蛋白氮和游离氨基酸在金华火腿加工过程中的变化

以60只浙江兰溪当地杂交猪后腿为原料，按传统工艺加工金华火腿，分析了股二头肌中非蛋白氮（Nonprotein nitrogen。NPN）和游离氨基酸（Free aminoacids，FAA）浓度随加工时间而变化的规律。结果表明，肌肉中的NPN和FAA含量都随金华火腿加工进程逐渐升高；NPN在后熟期和晒腿期间升高速度最快，而FAA在成熟过程中升高最快，成品火腿的蛋白质降解指数在14～20之间：成品火腿中的FAA占NPN的70％以上，其中以Arg、Glu、Leu、Lys、Ala和Val等含量较高。FAA总含最比腌制前提高13．8倍，火腿中大部分FAA浓度为腌制前的10-20倍，其中增加比例较大的FAA有Lys、Asp、Ser、Tyr和Ile等。火腿中大部分游离氨基酸的浓度多倍于其感觉阈值，因此可能对火腿风味的形成有重要贡献。

Muscle Changes of Non-protein Nitrogen and Free Amino Acids During Jinhua Ham Processing

Sixty experimental Jinhua hams were processed according to typically traditional processing technology with fresh hams from hind legs of local cross pigs of Lanxi, Zhejiang Province. Time-related concentration changes of non-protein nitrogen (NPN) and free amino acids (FAA) in biceps femoris during processing were assayed. The results showed that muscle NPN and FAA contents increased gradually during processing. The fastest increase of NPN content occurred during post aging and sun- drying periods, while FAA content increased most quickly at the loft-aging stage. The proteolysis indexes (P.I.) of the final Jinhua ham products were 14 to 20. More than 70% of NPN in final ham muscle was composed of FAA among which Arg, Glu, Leu, Lys, Ala and Val were dominant in concentration. The total content of FAA in Jinhua ham was 13.8 folds of that in prior-salting ham and the contents of most FAA were 5 to 20 folds higher than that in prior-salting hams, with Lys, Asp, Ser, Tyr and Ile being the FAA with relatively high increase rates. Since the concentrations of most FAA in final products were several times of their corresponding sensory thresholds, the FAA might have make an important contribution to the formation of Jinhua ham flavor.