Effects Of Superchilling,Composite Edible Coating And Modified Atmosphere Packaging On Fresh-keeping Of Half-smooth Tongue Sole (Cynoglossus Semilaevis) Fillets

Half-smooth tongue sole?Cynoglossus semilaevis,HTS?is mainly distributed in the Bohai and Yellow sea in China.With the improvement of high-density culture technology,the aquaculture quantity of half-smooth tongue sole shows an upward trend,which has developed into an important economic species of flounder in China.From the view of edible properties,half-smooth tongue sole is popular with consumers because of its delicious taste and high nutritional values,which is rich in high-quality protein,unsaturated fatty acids as well as essential mineral elements.Similar to other aquatic products containing abundant nutrient substances,the process of quality deterioration of can be enhanced because of negative changes environment factors,causing economic losses.Therefore,the study on preservation technology of half-smooth tongue sole has important practical guiding significance,and also has important reference value to improve the preservation technology of other flounder species.In this paper,the effects of temperature on the quality characteristics of half-smooth tongue sole were studied,and the shelf-life model was established based on the first-order dynamics model combined with Arrhenius equation.Secondly,different kinds of biological preservative combined with cold storage was used to study the positive effect of composite coating on the quality characteristics of half-smooth tongue sole.Finally,the synergistic effects of cold storage,composite biological preservative and modified atmosphere packaging on quality characteristics of half-smooth tongue sole was studied to maintain excellent quality and extend the shelf life of half-smooth tongue sole to the maximum extent.The specific research contents and corresponding results are as follows:1.Taking cultured half smooth tongue sole as the research object,and fresh fillets was stored at 10,4,0 and-3?.The changes of sensory,physicochemical and microbial parameters were observed regularly to study the effect of storage temperature on the quality characteristics of HTS fillets.The results showed that the changes of all indexes were consistent,with the prolongation of storage time,the sensory attributes,hold water ability and amounts of amino acids gradually decreased,while electrical conductivity,TVB-N,K value,biogenic amines and the total viable count increased.And cadaveric amines and rot were mainly accumulated of biogenic amines with stored time.The contents of amine and tyramine,glutamic acid and aspartic acid changed significantly during storage.All results showed that shelf lives of HTS fillets stored at 10,4,0,and-3?were 8,13,15,27 days,respectively.Low temperature can obviously delay the process of quality deterioration.2.The quality indices of HTS fillets were detected at different storage temperatures?270,273,277,283 K?.The shelf-life prediction model of each index was established by first-order dynamic model combined with Arrhenius equation,and its validity was verified by the variation characteristics of every index at 280 K.The results showed that lower temperature could significantly retard the changes of quality characteristics,maintaining excellent qulaity of HTS fillets.At the same time,there was an excellent accuracy of shelf-life model based on each quality index,and the relative error between the predicted and the measured value was less than±10%.Especially,the shelf life model based on TVB-N value and cooking loss showed more advantages in monitoring the quality characteristics of fillets.3.Taking cultured half smooth tongue sole as the research object,the compound edible chitosan coatings containing different concentrations of rosmarinic acid?RA,20,30,40 mg/kg?were prepared and applied for the fresh-keeping of half smooth tongue sole fillets.The quality parameters were measured regularly.The results showed that the changes rate of TVB-N,K value,TMA-N value,free amino acid content and growth of microorganism could be significantly delayed by chitosan edible coating including RA,especially 1%chitosan combined with 30 mg/kg RA.This effect was also reflected in water retention and water migration during refrigerated period.Overall,compared with the shelf life of HTS fillets without coating treatment for 12 d,chitosan-rosmarinic acid composite coatings prolonged the shelf life for 4⁶ days of fillets and up to 16¹8 d.Taking into account of cost factors,it can be concluded that the chitosan coating including 30 mg/kg RA was the best concentration ratio for maintaining excellent quality of fillets,which extended shelf life to 16 d at 4?.4.1%Chitosan edible coating incorporated with 30 mg/kg RA and different concentrations of?-polylysine??-PL?were prepared.Subsequently,fresh HTS fillets were treated by above prepared composite edible coating.And quality parameters were measured regularly during refrigerated period.The results showed that fillets treated HTS exhibited better effect on reducing the weight loss and cooking loss,suppressing the growth of microbial community,retarding protein degradation and keeping excellent sensory attributes as well as flavor properties during refrigerated storage compared with control gropus.However,0.1%,0.15%or 0.2%?-PL additions had similar effects in slowing down HTS fillets spoilage.Therefore,compared with the shelf life of HTS fillets without coating treatment for 10 d,1%chitosan containing 0.1%?-PL and30mg/kg RA can be utilized as a safe preservation method for extending shelf life of chilled HTS fillets by considerations of economy and the principle of using as little food additive as possible,which extended shelf life to 18 d at 4?.5.The effect of chitosan edible coating including rosmarinic acid and polylysine incorporated with different types of modified atmosphere packaging on the quality characteristics of HTS fillets was investigated.Relative results based on the regular determination of sensory,physicoichemical,microbial parameters showed that edible coating and modified atmosphere packaging treatment significantly delayed the spoilage process of fillets compared with fillets without any treatment and treated with composite edible coating alone.In a word,compared with the shelf life of HTS fillets with neither coating treatment nor MAP packaging for 12 days,the shelf life of half smooth tongue sole could be extended for 8-12 days with the combination of composite edible coating and modified atmosphere packaging.And 1%chitosan edible coating containing 30 mg/kg RA and 0.1%?-PL incorporated with 70%CO₂/30%N₂ showed the most positive effects on maintaining the excellent quality properties of HTS fillets,which prolonged shelf life to 24 d at 4?.