Effect Of Protein Changes On Quality Of Mouldy Fish During Processing

Moldy fish is a traditional flavor food in Ji’an and Fuzhou,Jiangxi Province,with unique flavor and salty flavor.During the traditional processing of moldy fish,a variety of substances in raw materials will degrade,oxidize and synthesize,resulting in quality changes.Taking the moldy fish as the research object,starting from the relationship between the oxidative degradation of protein and quality,this paper studies the impact of the changes of moldy fish protein on the changes of physical and chemical indexes and flavor components in different processing stages,so as to further understand the quality change mechanism of moldy fish.The main research contents and conclusions are as follows:1.The nutritional components,physicochemical properties,microorganisms and senses of moldy fish at different processing stages were evaluated.In the process of processing,the content of nutrients in moldy fish showed a downward trend;Fermented for 45-60 days,the moldy fish had good hardness and chewability.In the processing process,the content of microorganisms,oxidation value and nitrite met the food safety standards,and TVB-N(volatile base nitrogen)was slightly higher than the limit standard after 75 days of fermentation.The sensory score of fermentation preservation for 30 days was the highest,and the longest preservation time was 60 days.2.During the processing,the protein of moldy fish is degraded and oxidized continuously,denatured and crosslinked in the fermentation stage,forming protein aggregates,which affects the quality characteristics of moldy fish.In the later stage of fermentation,the hydrogen bond and nonspecific bonding force gradually weakened,and the hydrophobic interaction became the main force to stabilize the protein structure.In the later stage of fermentation,the nutritional value and quality of moldy fish decreased.Protein oxidative degradation had a positive effect on the quality and flavor of moldy fish in the early and middle stages of fermentation,and began to deteriorate in the late stage of fermentation.3.The changes of taste and volatile components in the processing of moldy fish were studied and analyzed by electronic nose,electronic tongue and GC-MS.The flavor of the samples changed significantly in different stages,and the samples had good repeatability.A total of 145 flavor substances were detected during processing,including 55 esters,21 alcohols,13 aldehydes and ketones and 16 acids.Esters,acids and nitrogen-containing compounds are the main flavor substances.Nitrogen and sulfur compounds begin to appear in the middle stage of fermentation and first decrease and then increase in the later stage of fermentation,It was found that the flavor quality of moldy fish was better when fermented for45-60 days.