Study On Refirgeration Technology Muscle Of Tuna

Tuna, distributed in middle and low latitudes, is a group of medium or largepelagic fish of the sea or ocean. They have high economic value. They are rich inDHA, EPA, other biological activity of polyunsaturated fatty acids, and high proteincontent, so they are recommended as one of three major nutrient fish by theinternational society for nutrition.The back of muscle of yellow fin tuna was research objects. Firstly, theessential nutrients (water, protein, fat, ash)、fatty acids (EPA, and DHA), and contentof necessary amino acids are assessed.Secondly, textural characteristics（the hardness、Springiness、Cohesiveness）biochemical properties (salt-solubility of myofibrillar proteins, Ca2+ATPase activities,SH content), freshness (K value、TVB-N value、pH value)，water holding power、Color of meat（a*）、TBA value、content of metmyoglobin are experimental targets.The back of muscle of yellow fin tuna were studied by measuring the indexes duringfrozen storage at different temperatures(-18℃，-25℃，-35℃，-45℃，-55℃), andfrozen180d, in order to find the best frozen storage temperature. Study resultsshowed that:1、The moisture content of Yellow fin tuna was up to72.35%, content of proteinwas25.53%percent, fat content was1.07％, ash was0.94%; K was493.08mg/100g,P was276mg/100g, Atrium was85.6mg/100g,Mg was29.06mg/100g, DHA25.34mg/100g、EPA6.32mg/100g. Thus, Yellow fin tuna was high in protein and low in fat.Their nutrition was very rich in aquatic product, and tuna meat could play a role ofbalanced diet nutrition.2、During frozen storage, the texture change of back muscle of tuna at differentfrozen storage temperature declined significantly (p＜0.05). When frozen at-18℃,the hardness of tuna changed maximum and frozen for six months, the hardnessdecreased from the beginning of22.7N to8.98N; the Springiness decreased from thebeginning of1.78mm to0.77mm; the Cohesiveness decreased from the beginning of0.45to0.06. When frozen at-25℃, the hardness decreased from the original22.7Nto10.39N; the Springiness decreased from the original1.78mm to0.77mm; theCohesiveness decreased from the beginning of0.45to0.11.-35℃frozen, thehardness decreased from the original22.7N to12.68N; the Springiness decreasedfrom the beginning of1.78mm to0.77mm; the Cohesiveness decreased from the beginning of0.45to0.17.-45℃frozen, the hardness decreased from the original22.7N to15.18N; the Springiness decreased from the beginning of1.78mm to1.39mm; the Cohesiveness decreased from the beginning of0.45to0.25.-55℃frozen, the hardness decreased from the original22.7N to17.01N; the Springinessdecreased from the beginning of1.78mm to1.46mm; the Cohesiveness decreasedfrom the beginning of0.45to0.31.3、During frozen storage, TBA value and content of metmyoglobin showed aupward trend but （a*）value showed a downward trend with frozen time increasing,The lower frozen storage temperature, the more slowly （a*）value decreased.，themore slowly TBA value increased, the lower corruption of fat, the better meatquality.Frozen at-18℃less than3months, meat got brown easily. At-25℃after6months, content of Mob reached to43％；At-35℃after6months, content of Mobreached to30％；At-45℃after6months, content of Mob reached to23％,colorslightly darker；At-55℃after6months, content of Mob reached to20％.4、At different frozen storage temperatures, freshness（K value、TVB-N value、pH value）showed a downward trend with frozen time increasing, but at differentfrozen storage temperature, it had different significant results. The lower frozenstorage temperature, the more slowly freshness decreased. Frozen at-18℃and-25℃only can be short term storage. At-35℃,can be stored up to six months.-45℃and-55℃as long-term storage temperature.-55℃frozen for six months, the k-valuewas about18%, so it can still do sashimi.5、The actomyosin salt-soluble protein content, Ca2+ATP activity, SH contentshowed a downward trend with frozen time increasing, The lower frozen storagetemperature, the more slowly Protein denaturation decreased.From all the above indexes, it can be safely concluded that the lower thefrozen storage temperature, the better tuna meat quality. But from the perspective ofeconomic, considerations,-55℃frozen six months and through data analysis,various changes compared with the meat is not significant, so look for a reasonablefrozen storage temperature for the production of high quality products is veryimportant.