A Novel Cryoprotectants Selection And Its Mechanism Study Of Cryoprotectants For Frozen Nile Tilapia(Oreochromis Niloticus)Surimi

The processing of surimi products is an important development direction of deep processing of fish in China.In recent years,fish balls,fish cakes,fish sausages and simulated crab meat products have been well received by consumers.The fish gills and surimi products processing industry have certain development prospects.Tilapia,an important economic fish in China,which has delicious taste,thick meat and rich of protein,has a certain development space for doing surimi.Because of sweetness and calories,traditional commercial cryoprotectants are harmful to special people.Therefore,it is necessary to search green cryoprotectants.In the past years,proteomics has obtained certain achievements in the field of food,such as two-dimensional electrophoresis?2-DE?,protein non-labeled quantitative technology?label free?,isobaric tags for relative and absolute quantitation?iTRAQ?and so on.Proteomics has been used to screen the differences in tilapia muscle protein during frozen storage,as a marker of the freshness of fish fillets.There are few reports on the anti-freeze mechanism of cryoprotectant on surimi by using proteomics.For above reasons,this paper was taking tilapia surimi for research,and the following researches were studied:SDS-PAGE gel electrophoresis,the characteristics of gelatin gel and protein physicochemical properties were employed to study the antifreeze effect of Epigallocatechin gallate?EGCG?on frozen tilapia surimi,and the anti-freezing mechanism of EGCG on the surimi was discussed.iTRAQ proteomics technology was used to study the different abundance protein between EGCG-added surimi and blank group surimi,and the anti-freezing mechanism of EGCG on frozen tilapia surimi at the protein level was conjectured.Combining EGCG with laver agar,and compared with traditional commercial cryoprotectant,the antifreeze effect of green cryoprotectant on frozen tilapia surimi was researched.The main results are showed as follows:1.During the frozen storage,the salt solubility,total sulfydryl content and Ca²⁺-ATPase activity of tilapia surimi was decreased with the extension of freezing time,and the carbonyl content of myofibrillar protein was increased.The strength of the glue and the water holding capacity are gradually reduced.EGCG could bind to hydrophobic groups of proteins through the action of covalent or non-covalent bonds,delay the release of hydrophobic groups,thereby inhibited the degradation of myofibrillar proteins,moreover,free radical scavenging ability and metal ion chelation ability of EGCG could also achieve this effect.In addition,the degradation of MHC,actin and unknown proteins?I,II?could be inhibited by EGCG effectively.The degradation degree of MHC is related to the quality of surimi.The anti-freezing effect of EGCG on frozen tilapia surimi was not proportional to the amount of EGCG-added.If the amount of EGCG is excessive,quality of the surimi would be deteriorated.The amount of EGCG added is 0.01%,which led to the best antifreeze effect.2.A total of 1769 proteins were identified in EGCG added and the blank group,and 36 proteins of which had significant differences.Through bioinformatics analysis,the 36 differential proteins were identified,which included structural proteins,transcription,translation and regulatory proteins and metabolic enzymes.The anti-freezing mechanism was that the degradation of structural proteins,the activity of endogenous enzymes,and proteins which were necessary for microbial proliferation were inhibited by EGCG.3.The anti-freeze effect of EGCG and seaweed agar mixture on frozen tilapia surimi is better than that of EGCG,while is not better than traditional commercial antifreeze.Despite this,EGCG and seaweed agar mixture could significantly improve the surimi gel strength and inhibit the content of protein carbonyl.In addition,the new cryoprotectant added to surimi in a small amount,which has the characteristics of low sweetness and low heat,has a certain application prospect.