Effects of Different Freezing Temperatures on Physicochemical Properties and Freshness of Spanish Mackerel

To investigate the effects of freezing temperatures(-50,-30 and-18℃)on freshness of Spanish mackerel,indexes such as pH,volatile basic nitrogen(TVB-N)value,2-thiobarbituricacid(TBA)value,the content of myofibrillar protein of the mackerel samples and sensory evaluation were measured.Using electronic nose technology,the smell information of Spanish mackerel after different freezing temperature treatment was obtained. The information data of electronic nose odor was analyzed by principal component analysis(PCA),and a rapid method to distinguish the freshness of Spanish mackerel was established. The results showed that there was significant distinction on freshness of the Spanish mackerel between different freezing temperatures(p<0.05). The freshness of mackerel samples under-50℃ freezing with fridge freezer was the best,the TVB-N and TBA value were significantly lower than the other two groups(p<0.05),while the pH and content of myofibrillar protein was significantly higher than the other two groups(p<0.05). At the same time,the sensory score of the freezing group at -50℃ was also better than the other two groups. According to the results of electronic nose,electronic nose could sensitively response to mackerels which well distinguish the different freezing temperatures. And the results were consistent with the results of physical and chemical and sensory evaluation. So the electronic nose could be used as a rapid detection method to distinguish the freshness of Spanish mackerels.