Study On The Quality Changes Of Frozen Spanish Mackerel

With the rapid development of pelagic fishery, the research of marine fish on stability and quality control in frozen storage is particularly important. Spanish mackerel, which has tender texture, nice favor, good nutrition and high diet health care functions, is one of the economic fish in the northern coastal of our country. The quality changes of Spanish mackerel and how temperature fluctuations affects the quality changes of Spanish mackerel during frozen storage are studied in this paper. The main contents of the paper are divied into the following two parts:Firstly, TVB-N, TBA value, myofibril protein content, histamine, p H value and the total number of bacteria were measured to evaluate the quality changes of the Spanish mackerel meat during frozen storage.The results suggested that TVB-N, TBA, pH value and histamine increased, while myofibril protein content and the total number of bacteria decreased with the extension of storage time from 210 days to 330 days.After 330 days frozen storage at-18℃~-22℃, TVB-N, TBA, the total number of bacteria and histamine values did not reach the maximum value of C hina. So Spanish mackerels could be kept in good quality stored at-18℃~-22℃, and the lower the frozen storage temperature is, the longer the shelf life is.Secondly, The total fillets were stored for 100 days and divied into four groups, the first group was stored under stable temperature of-18℃ and the other there groups were stored under unstable temperature, which exp erienced one temperature fluctuation cycle each week for six hours, and the fluctuation temperatures were respectively-10℃, 4℃, and 25℃. Sensory evaluation, physical and chemical examinations(TVB-N, TBA, myofibril protein content, histamine,pH value and TPA), mic rostructure observation and experiment on microbiology(the total number of bacteria) were performed to study the effects from temperature fluctuations on the quality of Spanish mackerel fillets during the frozen storage.The results showed that during the 100 days frozen storage, temperature fluctuations had great effect on TVB-N, TBA, myofibril protein content, histamine values and the total number of bacteria. The greater the temperature fluctuation, the greater the impact. After 100 days frozen storage, TVB-N of the groups that experienced 4℃ and 25℃ temperature fluctuations did not reach the maximum value of C hina. The result of TPA had highly correlation with that of sensory score, fiber structure observation, ice crystals structure observation and the protein denaturation condition reflected by the myofibril protein content. The greater the temperature fluctuation, the faster the degradation speed. Especially the groups that experienced 4℃ and 25℃ temperature fluctuations had the most obvious change.Therefore, frequently temperature fluctuations in the process of frozen storage will accelerate Spanish mackerel fillets’ quality degradation.