Study On Quality Changes And Control Of Fermented Fish During Storage

Fermented fish(Suanyu),with unique flavor and rich nutrition,is one of the typical representatives of traditional fermented aquatic products in China.Nowadays,it has great market development potential.Recently,researches in fermentation processing technology,safety quality and flavor formation mechanism of fermented fish have been reported.However,the information about the quality stability of fermented fish during storage is very limited.Therefore,the aim of present study was to investigate the quality changes of vacuum-packaged fermented fish during storage at different temperatures,and then combine with thermal treatment,irradiation and water retention technologies to improve the quality of fermented fish during storage.This study is of great academic value for a deep understanding of the storage characteristics of fermented fish during storage.Besides,it has an important guiding value in improving the quality stability of fermented fish during storage.1.Fermented fish was evaluated at refrigeration(4℃),room temperature(25℃)and harsh temperature(35℃)to investigate the potential for temperature abuse during distribution and storage.The changes of physicochemical,sensory,flavor and safty quality at different storage conditions were evaluated.The results showed that higher storage temperature(35℃)accelerated the moisture migration,texture hardening,sensory degradation,lipid oxidation and proteolytic degradation during 90-day storage.Significant decreases in the lactic acid bacteria,yeasts and total bacterial counts were observed.Samples stored at room temperature(25℃)had more stable quality compared with samples stored at 35℃.Compared with samples stored at 25℃ and 35℃,refrigeration(4℃)could better inhibit moisture migration and maintain texture,sensory,lipid,protein and microorganisms quality of fermented fish.Storage time had a significant influence on the flavor of fermented fish.Coliforms,Pseudomonas,Salmonella,and L.monocytogenes were not detected in any sample.S.aureus and V.parahaemolyticus were below the detection limits.The contents of biogenic amines in all samples were far below 200 mg/kg during the whole storage in all storage temperatures.Therefore,fermented fish had great changes in the texture and flavor quality during storage.However,all samples had higher safety for human consumption from the perspective of biogenic amines and microorganisms.2.Thermal and irradiation treatments were used to improve the quality of fermented fish during storage and in response to the microbial instability and impact of microorganisms and enzymes on the quality of fermented fish.Total bacteria counts,biogenic amines,total volatile base nitrogen(TVB-N),pH,texture,color,TCA-soluble peptides,free amino acids,peroxide value,fatty acid and flavor were evaluated.The total bacterial counts reduced sharply after thermal and irradiation treatments.Irradiation could significantly reduce total biogenic amines content of fermented fish.Total biogenic amines contents of all samples were at a low level(<65 mg/kg)and the pH values kept stable with range of 4.1-4.3 during the whole storage.Thermal treatment reduced the hardness,springiness and chewiness values.Irradiation and thermal treatments had effects on the color of fermented fish.The hardness of all samples increased during storage.The springiness,chewiness and color of fermented fish kept stable during storage.Compared with the control group,thermal treatment could effectively inhibit the production of TCA-soluble peptides,free amino acids and total volatile basic nitrogen.Irradiation treatment inhibited the production of TCA-soluble peptides and free amino acids to some extent.These two treatments had no significant effect on the initial total volatile compounds of the samples.However,both two treatments could inhibit the production of esters,alcohols,acids,alkenes and other compounds after 90 days storage.In summary,thermal treatments could inhibit protein degradation and better stabilize microorganisms,volatile compounds and physicochemical quality compared to irradiation treatment.However,thermal treatment had significant influence on the texture of fermented fish during storage.3.Water migration would deteriorate the apparent of fermented fish products.The improvements of the moisture migration with changing the degree of dehydration,packaging vacuum and adding water retention agent were evaluated by measuring moisture content,water holding capacity,water distribution and texture.The degree of dehydration had a significant effect on the initial moisture content of fermented fish.The water loss and the proportion of difficult-to-flow water decreased with the decreasing of the degree of dehydration during 30 days of storage.The hardness,chewiness and the proportion of bound water increased with the decreasing of the degree of dehydration during 30 days of storage.The water loss and freedom of bound water decreased with the decreasing of the vacuum degree the during storage.Meanwhile,the yeasts,staphylococcus and total viable counts slightly decreased with the decreasing of the vacuum degree.The low vacuum degree could maintain the hardness while the high vacuum degree could maintain the chewness of fermented fish.The addition of 0.6%trehalose had the smallest water loss,and the addition of 0.2%,1.0%trehalose and 0.15%sodium citrate also had relatively smaller water loss.Other groups had no obvious improvement effect on water loss of fermented fish.The addition of water retention agent could stabilize the texture.