Study On The Fresh-keeping Technology By Ice Slurry And The Cold Sterilization Technology Of Skipjack Tuna

By processing and preservation the frozen Skipjack tuna with the acidic electrolyzedwater (AEW) and ice slurry preservation technology, this study is aimed at investigating thesterilization effect of AEW, and the effect of preservation of AEW coating-ice and ice slurrypreservation technology during the storage period.The study can be divided into four parts:1. Nutritional components of the back muscles from Skipjack tuna were investigated.The results showed that: the content of water was71.53%, ash content was0.93%, contentof crude protein was26.04%, fat content was1.09%; contain a variety of essential mineralelements, and was rich of potassium, phosphorus and sodium; contain essential8kinds ofamino acids, and phenylalanine, lysine, methionine and tryptophan levels were higher thanthe FAO/WHO models and egg protein, and the first limiting amino acids was valine; DHAcontent was315mg/100g, EPA content was72mg/100g.2. The AEW coating-ice was investigated for its application in frozen Skipjack tuna.Further, the sterilization effect of AEW and some food condiments on Skipjack tunasashimi was also evaluated. The results indicated that:(1) The optimization composition ofthe condiments for the tuna sashimi is made up of8.0mL of vinegar,0.1g of mustard,1.0mL of AEW and a small amount of rice-adding wine.(2) Under-18℃frozen conditions,the total numbers of bacteria in frozen Skipjack tuna with AEW coating-ice reducedsignificantly.(3) After320day storage, the content of TVBN in frozen Skipjack tuna whichwere coated with AEW ice was rang from16.49to17.82mg/100g, significantly better thanthe frozen Skipjack tuna which were coated with distilled water whose content of TVBNwas22.13mg/100g in.(4) The AEW coating-ice could keep the frozen Skipjack tuna ingood color and textural properties. This study can lay the theory foundation for a new icecoating technology suitable for the frozen tuna, and further provide a scientific guidance forthe product of ready-to-eat tuna sashimi.3. Compared with traditional freshwater ice, to study the effect of ice slurry treatmenton the physicochemical properties and microbial characteristics. The results indicated that:(1) After18d refrigerated(-4℃), the sample treated by ice slurry can keep the value of pH,TVB-N, TBA, a*and the total viable count at5.57,10.2mgN/100g,2.87mg/100g,8.92and2.61lgCFU/g, while the sample treated by freshwater ice keep the value at6.05、20.3mgN/100g,6.60mg/100g,7.16and3.02lgCFU/g, the values of spring and chewiness ofthe processed meat in slurry ice were1.19mm and5.50mJ respectively, and the sampleschilled in freshwater ice were0.95mm and3.32mJ, ice slurry preservation treatment showed significantly effect on Skipjack tuna(p<0.05).(2) After8h analog salespreservation (25℃), compared with blank and freshwater ice preservation treatment group,the sample value of pH, TVB-N, TBA, a*, the total viable count and textural propertiestreated by ice slurry were significantly lower(p<0.05); the a*value of muscle issignificantly higher than blank group(p<0.05), but has no significance effect compared withcrushed ice preservation group. Ice slurry preservation can significantly slow the corruptionprocess of the fish, extend the shelf life, so it can satisfy the long distance transportation ofice fresh aquatic products.4. Compared to a blank batch and a batch chilled in traditional flake ice, and furtherthe functional properties of the proteins in Skipjack tuna were also evaluated during thestorage(-4°C). The results indicated that:(1) the prepared slurry ice has a spherical shape,with smooth surface, high unit surface area and good flowing property. The temperature ofthe skipjack tuna meat can decrease from35°C to1.3°C within8min, after treated with theslurry ice.(2) The content of myofibrillar protein, the activity of Ca2+-ATPase and–SHwere decreased and the protein degradation degree were raised in the three treated-groups(the blank, flake ice and slurry ice treatment.(3)after18days storage at-4°C, while thequality of the samples treated with the slurry ice was significantly higher than the other twotreatments (p<0.05).(4)In addition, the slurry ice treatment was also showed a good resulton the inhibition of myoglobin autoxidation and the preservation of the meat color. Theseabove findings confirmed that the slurry ice had shown to be a suitable medium forprevious storage of Skipjack tuna.