Optimization of water thawing process for tuna chunk based on the decomposition of NAD

To optimize the techniques of water thawing for high- quality tuna,tuna was taken from-60 ℃ ultra- low temperature refrigerator and then kept it in- 12 ℃ to 0 ℃ low temperature refrigerator for the corresponding time then proceeded water thawing.Results showed that after being stored in-6 ℃ for 15 hours and-9 ℃ for 3 days,water thawing effectively relieved shrinkage of tuna and reduced drip loss,comparing with direct water thawing,also the chewing characteristics was improved and there was no significant difference between the refrigerated thawing and the method used in this study was improved.Additionally,changes of contents of adenosine-triphosphate( ATP) and nicotinamide adenine dinucleotide( NAD) in tuna during the process of water thawing optimization were tested and analyzed.The results showed that when the decomposition of NAD to 0.20 μmol / g and the degradation of ATP to 2.0 μmol / g,the shrinkage of tuna was relieved and the drip loss was reduced,also the K value was less than 20%. In conclusion,the optimization for water thawing can effectively improve the quality of frozen tuna.