Effects Of Lipid Hydrolysis And Oxidation On The Flavor Formation Of Hubei Traditional Fermented Ham

Chinese fermented ham has a leading position in traditional meat products in Hubei Province.Xuan'en ham is an outstanding representative of the traditional fermented hams in Enshi Prefecture of Western Hubei Province,and consumers all like its unique flavor.Currently there are few study reports about the flavor of Xuan'en ham.This study aims 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 Xuan'en ham during processing.Then the effects of lipid changes on the formation of flavor compounds are analyzed to have a scientific understanding of flavor formation mechanism about the Xuan'en ham,so that to provide a theoretical basis of traditional techniques and parameters.1.Studies on the lipolysis during processing of Xuan'en hamSelect first sign,second sign and third part of ham then pick off the bones and skins to mix up,the three parts of the samples from 6 hams randomly taken at fresh ham,end of salting,initial of fermentation,middle of fermentation,end of fermentation,and production were used to analyze.Results showed that: during the processing of Xuan'en ham,lipids hydrolysis continue to occur,there is 60.41%,35.69% and 41.75%of phospholipids hydrolyzed in the sliced ham,the subcutaneous fat,and the intramuscular fat.Phospholipid is the important prerequisite flavor in lipid.The component of oleic acid,linoleic acid is higher in free fatty acid.The change of them is obvious during processing of Xuan'en ham,which are the important flavor compounds of lipid.2.Studies on the changes of lipase and phospholipase activity during processing of Xuan'en hamThe neutral lipase activity is the highest part of the skin,followed by acid lipase,acid phospholipase activity is minimum in the sliced ham and the subcutaneous fat,while in the intramuscular fat,the neutral lipase is the highest part of the skin,followed byphospholipase,acid lipase activity is minimum.The activity of three enzymes is declining processing of Xuan'en ham.Phospholipase may be the important enzyme of fat degradation.Temperature and salt content is the larger factors,which play an important role in enzyme activity.3.Studies on the changes of lipid oxidation and lipoxygenase activity during processing of Xuan'en hamDuring the processing of Xuan'en ham,the acid value was rising,indicating that the content of free fatty acids was increasing;the TBARS increased at first and then decreased,indicating that aldehydes were further oxidized to carboxylic acids with the increasing of temperature in the fermentation processing,acid-aldehydes constantly changed.The polyunsaturated fatty acids in free fatty acids and phospholipids were declining with the deepening of fat oxidation,polyunsaturated fatty acids may be the main part in the reaction of lipid oxidation,which plays an important role in the flavor forming of ham.The carbonyl value changed relatively stable in the overall trend,but was still higher than fresh ham,indicating that small molecule carbonyl compounds accumulate constantly.During the processing of Xuan'en ham,the lipoxygenase showed a certain degree of vigor and vitality of the same trend in the whole process,and reached the highest after the salt,promoting the oxidation of lipids in the sliced ham and intramuscular fat.The lipoxygenase potential activity,which was not measured in subcutaneous fat,speculated that the oxidation of subcutaneous fat may be mainly caused by auto-oxidation.4.Studies on the changes of flavor compounds in dry-cured Xuan'en ham during processing by SPME-GC-MSThe flavor compounds of Xuan'en ham are aldehydes,alcohols,carboxylic acids,ketones,esters,alkyl olefins and other substances,including furan,pyridine,sulfur compounds and so on.Lipid is the most important flavor precursors,and the flavor in the intramuscular part of production,which came from fat oxidation directly,was 55.71%;from the degradation of amino acids was 16.81%,from the reaction of Maillard was1.42%;the flavor in the subcutaneous part of production,which directly came from fat oxidation,was 57.40%,from the degradation of amino acids was 8.87%,from the reaction of Maillard was 2.38%;the flavor in the sliced ham part of production,which directly came from fat oxidation was 54.48%,from the degradation of amino acids was11.19%,from the reaction of Maillard was 0.69%.