Study On The Hydrolysis And Oxidation Of Lipide And Protein In Low Sodium Traditional Jinhua Ham During Processing

Jinhua ham is a typical representative of traditional dry cured meat products in China,and is also one of the world's most famous ham.It is favored by consumers for its unique flavor and special taste.Jinhua ham has a history of nearly one thousand years.Generally traditional Jinhua ham has high salt content which is general several times higher than other food.However excessive intake of sodium can cause harm to the health.Therefore,the development of low sodium Jinhua ham has importantly practical significance.According to experiment design,the research comprises three parts:first,the study on the changes of physicochemical properties,lipolysis and oxidation of low sodium traditional Jinhua ham during processing;second,analysis of the protein degradation and the antioxidant of polypeptide of the low sodium traditional Jinhua ham during processing;third,the research of volatile compounds and sensory quality of low sodium traditional Jinhua ham during processing.1.Study on the changes of physicochemical properties,lipolysis and oxidantion of low sodium traditional Jinhua ham during processing.The water content and water activity of the low sodium group decreased in line with the trend of salt group slowly during processing.There was no significant difference between the two groups in every processing stage.The pH value of the low sodium group was significantly higher than that of the salt group in the middle of ripening.The sodium content of final product was 1.959%,which was 52.94%lower than that of the salt group.Neutral lipase activity was the highest,followed by acid lipase,and phospholipase was relatively lower during processing.The activities of these enzymes decreased gradually during processing,but remained active in the end of ripening.They played an important role in lipolysis.The carbonyl value and conjugated value changed in volatility during processing,but the changes in all the stage did not show significant.The TBARs value began to rise at first and then reduced during processing,and reached the highest level in the end of sun drying.The TBARs value was greatly higher in low sodium group than that in the salt group in the end of ripening.2.Analysis of the protein degradation and the antioxidant of polypeptide of the low sodium traditional Jinhua ham during processing.Total nitrogen content of two groups slowly increased during processing,so did the non-protein nitrogen.At the end of processing,the proteolytic index(P.I.%)of low sodium group was 23.45%,which was higher than salt group(20.52%).The muscle protein was hydrolyzed continuously during processing,which generated a lot of free amino acid(FAA),such as Glu,Ala,Leu and Lys.They were in high concentration in the final products.Most FAA play an important role in the flavor,and the concentration of these FAA were much higher than their sensory thresholds.Muscle cathepsin B displayed similarly activities in two groups which all dropped gradually during processing.The activity of cathepsin L declined at first during processing but then increased during sun-drying stage.The residue activities of cathepsin B and L were 14.41%and 34.28%respectively,when they reached their final stage.The DPPH radical scavenging activity of peptides extracted from low sodium Jinhua ham was 94.53%.The hydroxyl radical scavenging activity of the low sodium group was lower than that of the salt group(57.24%),which was 56.59%.The total antioxidant capacity in the low sodium group was 5.51.The ACE inhibitory activity of peptide extracted from low sodium group was 40.65%.3.Research on volatile compounds and sensory quality of low sodium traditional Jinhua ham during processing.SPME-GC-MS was used to identify volatile flavor compounds,61 kinds of compounds had been identified in two groups in the final products.The compounds identified included 14 kinds of esters,31 kinds of aldehydes,8 kinds of alcohols,7 kinds of hydrocarbons and carboxylic acids,5 kinds of ketones,4 kinds of pyrazine,and 1 kind of furans.With the extension of the processing time,the L values decreased,a*values increased and b*values decreased,but there was no significance between the low sodium group and salt group in color.The hardness of texture index increased during processing,and the value of hardness in low sodium group was lower than that in the salt group.Sensory score of salt group was 51.9,just bigger than that of low sodium group,but the difference was not so significant.Finally,sensory analysis showed that the final products of low sodium group not only kept the traditional flavor of Jinhua ham but also displayed bright red color and high juiciness.