Studies On Changes Of Lipolysis, Lipid Oxidation And Main Flavour Composition In Goat Legs During Dry-curing And Ripening Processing

Goat meat is one of the widely consumed meats in the world.However,its special odour causes low consumption.Dry-cured ham,as one of the most significant of air-drying and ripening animal products,is well-known because of its flavor,color and taste.In Xinjiang province of China,local people have the custom of curing the goat meat and keeping it outdoor for air-drying and ripening to special products.The aim of this paper is to explore the new processing technology for improving sensory qualities of goat legs by using dry-curing and ageing process of traditional ham in order to provide a theory and technology basis for developing goat meat new products.The contents and results of each chapter are as follows:1) Studies on curing and air-drying and ripening processing technique and parameters of goat legsThe process of curing and ageing of goat legs was researched by using Jinhua ham traditional process.The index of chemical compounds,textures,and sensory evaluation were analyzed during processing.Results showed that:water content decreased and the content of sodium chloride increased with the processing,which were 48.86%and 9.41%at 60 days of aging respectively,pH values in goat legs was no significant changes(P＞0.05). The hardness,adhesiveness,springiness and chewiness of goat legs increased,cohesiveness and resilience decreased with the processing.The results of sensory evaluation:the score of flavor content,flavor intensity and overall appreciation arrived highest at the process point of 20 days ageing.The process parameters of curing and air-drying and ripening for goat legs were salting-curing 20 days(8℃,60%RH),air-drying stages 20 days(15-20℃;80% RH);ageing stages 20 days(20-30℃;90%RH).2) Lipolysis and lipid oxidation in goat legs during processingThe lipid oxidation and lipolysis in biceps femoris muscle were studied by analyzing FFA,TBARS,conjugated diene value at 6 processing and the relationship with temperature and relative humidity.Results showed that:the total of lipids content and triacylglycerol increased(P＜0.05) during the processing,but phospholipids decreased.FFA content increased before the stages of 20days air-drying,arrived highest at ageing for 20 days (459.25mg/g lipid).Palmitic acid,linoleic acid,Linoleic and stearic acid were main free fatty acid in goat legs,and linoleic was the main free fatty acid forming the flavor of goat legs by oxidation.TBA values increased before the stages of 20days air-drying arrived 0.28μgTEP·g^-1 at the stages of 20days drying and ageing,then decreased;conjugated diene value increased totally.Salt content and temperature had significantly influence on lipid oxidation(R²=0.907 and 0.603 respectively).3) Studies on the flavor compounds of goat legs during processingFlavor compounds in biceps femoris of goat legs were extracted and identified by solid phase microextraction(SPME) GC/MS system during processing.Main flavor compounds was identified in the analysis method of CPA(principal component analysis). The flavor compounds in final products of goat legs was clustered in the following chemical families:alkanes and alkenes,aromatic hydrocarbons,alcohols,aldehydes, ketones,carboxylic acids,esters,oxygenous heterocycle compounds,nitrogenous compounds,sulphur compounds,chloride compounds,amides and terpenes.The content of aldehydes is highest,accounting for 37.46%of total flavor compounds.The first principal component of the flavor compounds in final products was a group dominated by aldehydes (2-methyl-,Butanal;3-methyl-,Butanal;3-methyl-,Butenal;Decanal;Heptanal;Hexanal; Nonanal).The second principal component was a group mainly dominated by alcohols (Ethyl alcohol;1-Octen-3-ol;1-Penten-3-ol;Heptanol;Hexanol;2-ethyl-,Hexanol) and acids(3-methyl-Pentanoic acid;Acetic acid;2-methyl-,Butanoic acid),which had a multiple origins.The two first principal components of biceps femoris explained 56.79% and 24.31%of the total variance of the flavors respectively.The branched compounds such as 4,5-dimethyl,Nonane;2,2-dimethyl,Pentane;3,3-dimethyl,Heptane could have the connection with the goat special odour(4-methyl octanoic acid and 4-methyl nonanoic acid).