Effect of storage temperature on quality and the freshness of tuna

The quality changes of tuna,storage in-4 ℃( partial frozen),-2 ℃( freezing temperature) and 4 ℃( cold storage),was studied by sensory assessment,p H,K values,histamine concentration,total volatile basic nitrogen( TVB- N),met- myoglobin concentration and aerobic bacterial count. The results showed that the K values,histamine concentration,total volatile basic nitrogen( TVB- N),met- myoglobin concentration and aerobic bacterial count of tuna increased during storage,regardless of the storage temperature,increasing at a faster rate at higher storage temperatures,the TVB- N value stored for sixty hours at- 4 ℃ and- 2 ℃ were 10.83 mg /100 g and12.77 mg /100 g respectively,however,it reached 17.12 mg /100 g and exceed the limit of 15 mg /100 g when tuna was store at 4 ℃ for fifty- six hours. The increase of histamine concentration was not evidence at both- 2 ℃ and-4 ℃ throughout the storage,but it rose remarkably at 4 ℃.Compared with cold storage,the partial freezing and controlled freezing point condition would increase the shelf- life of tuna obviously.