Effect Of Acidic Electrolyzed Water Pretreatment On Quality Of Sturgeon During Ice Temperature Storage

In recent years,annual aquacultural sturgeon output is steadily kept about 90,000 tons,accounting for more than 90% of the total world output of sturgeon.According to investigation,almost all the sturgeon meats are kept in frozen state in the market or processing factory.Although frozen storage could provide meat with long shelf life,but would damage the processing and “eating” quality of the meat.Frozen storaged meat could not meet the preference of consumers in China and other Asian countries.Thus,research on non-frozen sturgeon meat quality change and control under nonfrozen state will benefit the further expansion of sturgeon mea market and sturgeon aquaculture industry.Critical challenge of non-frozen fish meat is spoilage caused by spoil bacteria.So,reducing the original bacteria number in the beginning of storage is one of the most efficient strategies of quality control.In this presentation,fresh hybrid sturgeon meat was taken as raw material,the effect of acidic electrolyzed water(AEW)on reducing the initial bacteria number on the sturgeon meat and its further effect on the following storage quality during ice temperature storage(-1℃)were investigated and discussed.This work could provide some theoretical and technical support for improving the quality of sturgeon meat and shelf life elongation during ice temperature storage.First,the quality change of sturgeon meat under ice temperature storage was investigated by some measures,including texture analysis,stability of S-1 and rod fraction of myofibrillar protein,ATPase activity and storage modulus G’ value.At the same time,meat quality change during chilled storage at 4℃ and frozen storage at-20℃was also studied for comparison with the quality change during ice temperature storage.Results showed that 1)Hardness of sturgeon meat reduced quickly after storage for 6d and then the reducing rate slowed down;springiness reduced significantly after 3d,then kept stable till the end.2)Myofibrillar protein extraction yield increased after storage for 6d.3)ATPase activity of the myofibrillar protein and storage modulus G’ value decreased quickly and in a descending sequence of 4℃>-1℃>-20℃.4)The extracted myofibrillar protein was stored at 4℃,-1℃ and-20℃,the quality change is consistent with that of the meat storage.Degradation degree of the rod and s-1 fraction was also in a descending sequence of 4℃>-1℃>-20℃.Second,a series salt solution was used to prepare acidic electrolyzed water(AEW),and the electrolysis time and HCl concentration added were optimized.The prepared AEW was used to treat the sturgeon meat and its decontamination effect and mechanism were evaluated.Results showed that 1)After the AEW equipment beginning to work,pH value and available chlorine concentration(ACC)fluctuated within a small scale.The properties of AEW was stable after working for 5min.2)With the increase of added HCl in salt solution,AEW with lower pH and higher oxidation reduction potential(ORP)and ACC could be obtained.3)Longer treating time and greater the amount of AEW could produce better decontamination effect on sturgeon meat.An optimized treating time was 10 min with an optimized material to liquid ratio of 1:10.4)The microflora of the sturgeon meat changed obviously after treated by AEW with ACC of 36、49、67mg/L.The initial dominant bacteria was Acinetobacter(70.27%)and Shaewanella bacteria(18.92%),with others minor species of Pseudomonas(2.7%)and Exiguobacterium(2.7%).After treated by AEW,number of Acinetobacter obviously decreased,but Shaewanella bacteria remained stable,Exiguobacterium disappeared completely and Buttiauxella,Serratia and Aeromonas newly appeared.5)After treated by AEW,the whiteness of sturgeon meat increased obviously.6)Take seven bacteria strains separated from sturgeon meat as target,the decontamination effect of AEW with ACC of 36、49、67mg/L was significant especially when there was no culture medium in the bacteria solution.Staphylococcus saprophyticus was the only strain could be detected after treated with AEW with ACC of 67mg/L(without LB media).Staphylococcus saprophyticus showed the strongest tolerance to AEW,but Staphylococcus xylosus1 was the most sensitive one.As the ACC increase,the concentration of the soluble protein and electrical conductivity in the supernatant of the treated bacteria solution increased gradually.Finally,AEW with ACC of 36、49、67mg/L was used to treat sturgeon meat and then the storage quality was evaluated.Results showed that 1)Comparing with the control group,the initial bacteria number was significantly reduced after AEW treatment.Total volatile base nitrogen(TVB-N),K value,pH value and thiobarbituric acid value(TBARS)of the treated group was lower than that of the control group.AEW treatment retarded the quality deterioration effectively.AEW with ACC of 67mg/L demonstrated the most outstanding effect on freshness and quality control.2)As the storage progressed,diversity of microflora decreased greatly,Pseudomonas percentage increased gradually and reached 70%～90% at the end of storage;3)According to total number of bacterial colonies,TVB-N and K value,the shelf life of sturgeon meat was extended by 2,6,9 days,2,7,11 days,3,7,9 days respectively,after treated by AEW with ACC of 36,49,67mg/L.In conclusion,AEW showed desirable sterilization effect on sturgeon meat,improving the quality of sturgeon meat under ice temperature storage,retarding the quality deterioration and prolonging the shelf life.But the chloride residual in sturgeon meat and other quality issues raised by AEW need to further investigation.