Studing On The Changes Of Lipid And Flavor Compounds During Processing Of Jinhua Ham

Jinhua ham is a famous dry-cured meat product in china and South-east Asia, and also one of the most famous dry-cured hams in the world. Jinhua ham, with a long production history of over 900 years, has a very strong flavor characteristic and is enjoyed by consumers. Up to now, the laggard processing technology adopted in small-scale workshops has influenced the sustainable development of Jinhua ham seriously. The main reason is the deficiency in theory research. This leads to the poor understanding on the scientific meaning of the traditional processing technology of Jinhua ham; and no theory can be used in optimizing the duration and parameters in practice. This research is a part of the item entitled "producing technology and products exploitation for Chinese traditional & character food and animal products"(2002AA248031) under the high technology and development program of P. R. China. The aim is to investigate the forming mechanism and pathways of flavor substances originated from lipid by studying the changes of lipid as a main precursor of flavors and analyzing the flavor substances of Jinhua ham during processing; elucidate the role of lipid in formation of flavors; provide a theory basis in improving the processing technology and realizing the industrial production of Jinhua ham. The contents and results are as follows. 1. Studies on the lipolysis during processing of Jinhua hamExperimental Jinhua ham were processed by traditional processing technology with 60 hind legs weighed 6.2-6.9 kg from local Liangtouwu cross-bred. Biceps femoris and subcutaneous fat samples from 5 hams randomly taken at the green ham stage, end of salting, end of sun-drying, middle of aging, end of aging, post-aging (1) and post-aging (2) were used to analyze the changes of contents of lipid, triacylglycerol, phospholipids, free fatty acids and relative indices. Results showed that: triacylglycerol contents in lipid of biceps femoris and subcutaneous fat did not change significantly during processing. The triacylglycerol contents in lipid of biceps femoris and subcutaneous fat were 72.74% and 91.68% at the green ham stage, which were 87.59% and 89.94% at post-aging (2), respectively. While the phospholipids contents in lipid of biceps femoris and subcutaneous fat changed significantly during processing. About 66.67% and 77.22% of the totalphospholipids in biceps femoris and subcutaneous fat were hydrolyzed during processing of Jinhua ham. The R2 of phospholipids and triacylglycerol contents with free fatty acids contents were 0.91/0.67 0.97/0.94, respectively. Results analysis showed that, the main source of free fatty acids was phospholipids. Phospholipids were the main precursor of flavor substances. Analysis of free fatty acids showed that, the proportion of saturated and monounsaturated fatty acids in biceps femoris and subcutaneous fat increased during processing, among which the proportion of monounsaturated fatty acids increased more strongly; the proportion of polyunsaturated fatty acids decreased during processing. These indicated that the polyunsaturated fatty acids were the key fatty acids in lipid oxidation during processing of Jinhau ham. Change of linoleic contents, which decreased 4.48% and 5.58% in biceps femoris and subcutaneous fat respectively, was much significant than the other fatty acids during processing. Linoleic was the main free fatty acid in flavor formation by oxidation.2. Studies on the changes of lipases and phospholipase activity during processing of Jinhua hamSamples mentioned above were used to analyze the changes of acid and neutral lipases activity, phospholipase activity and relative indices in biceps femoris and subcutaneous fat during processing. Results showed that, in biceps femoris, the activity of neutral lipase was the highest; activity of acid lipase was the lowest. The potential activity of the three enzymes decrease during processing. The activity of neutral lipase, acid lipase, phospholipase, which could not be measured at post-aging (2), changed from 5.332U/h.g protein, 1.957U/h.g prote...