Quality Change Of Goldedn Pomoano Fillet During Partial Freezing Storage And Control

Goldedn pompano is delicious and is favored by Chinese people and those in other Asian countries,especially the fresh one.But fresh fish is easily subjected to autolysis and spoilage.Among all the non-freezing storage techniques,partial freezing could reduce the drip loss and other quality issues caused by frozen storage.Comparing with chilled and iced storage,it could elongate the shelf life.Besides,reducing the initial bacteria number is an effective strategy to control the fish freshness caused by spoilage microbe.In this presentation,goldedn pompano was used as target material,the effect of decontamination pretreatment on goldedn pompano fillet was investigated and the quality change during partial freezing storage.Firstly,-1.28?is the freezing point of goldedn pompano,and-3?was considered as partial freezing temperature.The quality change during storage was studied and the relationship with endogenous protease was discussed.Results showed:the hardness,chewiness and thiol content in sarcoplasmic protein and myofibrillar decreased gradually,obvious degradation of S-1 and segments in myosin occurred after 12d and almost disappeared after 27d,degradation rate of rod was a bit quicker than S-1;casein zymograghy method was optimized to measure Calpain activity:0.2%casein,ionic strength of 100mM Tris-HCl in protease extraction buffer,incubation buffer pH of 7.3 with 6mM Ca²⁺.Both?-Cal and m-Cal showed high activity before 4d,?-Cal activity disappeared after 8d.Activity of m-Cal disappeared after 20d;the activity of CatB and CatB/L decreased at the early storage stage and lowered to 56.4%and 50.5%after 8d.The activity kept relatively stable and decreased after 20d.SP activity was stable at the early storage stage and decreased quickly after 12d and got to the lowest point after 20d,but increased after that.Results suggested endogenous protease was active during partial freezing storage.The fillet quality change at early stage was relevant with Cat and?-Cal,medium stage with m-Cal and SP,and later stage with Cat and SP.The increase of SP in the end might originate from spoilage microbe;the activity of CatB,CatB/L,SP and Cal was stable below 40?,CatB,CatB/L and SP demonstrated stable activity at pH 5.0,5.5 and 8.0.total plate count?TPC?by 2 logCUF/g,and the TPC of treated group kept lower than that the control group,but the residual bacteria grew faster than that of the control;The initial bacteria in control group were mainly composed of the genus shewanella?86.36%?and Aeromonas?13.64%?,and the number of Pseudomonas and Brochothrix increased during storage;Decontamination treatment could postpone the decreasing rate of ATPase and denaturation rate of myosin.Peak value of storage modulus of myofibrillar protein declined gradually,the value of ClO₂ treated group was higher than the control.The value of HCl treated group was similar with the control but higher after 24d,with not more than 15pa for the control and more than 50 pa for the HCl treated group;After treated by ClO₂ and HCl,pH of the fillet was lowered,and further declined at the early storage stage and then ascended,but the value of treated group was lower than the control,and ClO₂ group was lower than HCl group.The result of TVBN showed that the fillet of control,ClO₂ and HCl group was kept in first grade freshness before 20,27,24d respectively,kept acceptable before 25,32,29d.The K value of above three group reached 40%after 13,20,21d.Finally,the effect of several metal ions and NaCl concentration on the ATPase activity was evaluated.Results showed that Mg²⁺and higher concentration of K⁺??0.6mM?could increase the ATPase activity;Ca²⁺?Zn²⁺and lower concentration of K⁺??0.6mM?could inhibit the activity;The increase of NaCl concentration inhibits the activity of ATPase.In conclusion,partial freezing could keep the freshness of goldedn pompano fillet obviously,elongating its shelf life,quality change during partial freezing storage was relevant with endogenous SP and Cat.After treated with 30ppm ClO₂ and HCl?pH2?,the shelf life was prolonged 7 and 4d,respectively.Various metal ions of different concentrations can activate or inhibit the activity of myofibrin ATPase,it provids more possible way to control the quality of pompano,and will benefit further research on the freshness control technique of pompano.