Research On Lipoxygenase And Flavor In Rugao Ham

One hundred and ninety-two hind legs of crossbreed pigs were purchased within a day when slaughtered, with the weight of 7.87±1.01kg. These legs were processed with traditional method in Jiangsu Longlife Group from Jan., 2007. The biochemical character of lipoxygenase in raw material, lipolysis and lipid oxidation during processing and volatile flavor compounds during processing were studied, and further, the relationships between lipoxygenase and lipid oxidation, and between lipoxygenase and flavor were both discussed.Biochemical character of lipoxygenase in biceps femoris of raw material of Rugao Ham was studied through certain purification. It was showed that lipoxygenase in raw material of Rugao Ham could be purified through 20%～40% ammonium sulfate saturation, DEAE-Sephacel column and Phenyl-Sepharose column, with a purification factor of 65.4, a molecular weight of 96.96kDa and a maximum activity at 25℃, pH 5.0 and 6.0. The optimum substrate of lipoxygenase in raw material of Rugao Ham was linoleic acid, with a concentration of 0.625mmol/L, followed by arachidonic acid and linolenic acid.Hams at different processing stages including green ham, end of salting, end of sun-drying, middle of loft-aging, end of loft-aging and post-aging were sampled and measured in order to reveal the rule of lipolysis and lipid oxidation in Rugao Ham during processing. It was showed that FFA content first increased sharply and then decreased gently, among which the PUFA, maybe more sensitive to oxidation, declined most significantly. Changes of PUFA containing cis, cis-1, 4-pentadiene units and SFA were most significant. Lipid oxidation existed continuously during processing of Rugao Ham, more sharply after sun-drying than before.Meanwhile, volatile flavor compounds of hams at different processing stages mentioned last chapter were determined by SPME-GC/MS. 152 volatile compounds were detected in the study. Flavor formation began from the salting stage, and gradually transformed when loft-aging. Contribution to flavor by lipid decreased during processing. Aldehydes were most important volatile flavor compounds, followed by alcohols and carboxylic acids. In the final Rugao Ham, 12.03% were derived from lipolysis and lipid oxidation, while 36.16% from degradation of amino acids. Correlation analysis indicated that contribution to lipolysis and lipid oxidation by lipoxygenase was insignificant, and lipid oxidation was mainly photosensitized oxidation and auto-oxidation. Contribution to flavor by lipoxygenase was also insignificant.