| The common carp,grass carp,silver carp and bighead carp were used as the research materials in this paper,and the differences on physiological and biochemical indexes of the four freshwater fish during storage at 40C were studied.The results of variance analysis indicated that the difference of storage qualities on the four fish was very small,So the common carp was chosen as the main research material,the effects of ice temperature and cold storage conditions on changing of storage qualities of common carp were systematically studied by the detecting techniques,such as,color difference meter,electronic nose,texture analyzer,LF-NMR and sensory evaluation.Then,the effect of pulsed light sterilization on the shelf life extension of common carp was explored.This research enriched fresh-keeping theories of freshwater fish and lays some theoretical foundations of freshwater fish storage.The main results were as follows:1.There were some differences on indexes of physical and chemical quality and moisture migration of the four kinds of fish(common carp,grass carp,bighead carp and silver carp)during storage.However,the differrences were very small.The effects of storage time on the color and texture properties of common carp were relatively significant.The moisture migration and volatile components of common carp made a significant changing during storage.The indexes of TVC,TVB-N,K value of the four species fish all reached below the lower limit at the 6th day of storage,and this illustrate that their shelf life during cold storage was about 6 days.The results of texture analysis,water mobility,TVC and K value indicated that the spoilage rate of common carp was little faster than the other three.2.The results of sensory evaluation of carp blocks under different storage temperature showed that,the sensory score of carp under-2 C was significantly higher than that under 4℃;In the aspect of color changing of carp,the color difference values which under-2℃and 4 C were all significantly correlated with storage time,and the carp color under-2 C changed slower than that under 4℃.The results of electronic nose detecting showed that,Linear Discriminant Analysis(LDA)was better than Principal Component Analysis(PCA)for characterizing the volatile compounds changing of carp during ice storage and cold storage.The springiness indexes of carp were all significantly correlated with the storage days under the two storage temperatures(p<0.05),and this indicated that,the storage time had great influence on springiness of carp.The combined water of carp blocks exhibited little change during storage,but the immobilized water and free water migrated significantly under ice and cold storage,and the changing trend of migration of moisture at-2℃ was more stable.The texture characteristics of fish at 4℃ changed more distinctly as the extension of storage time.The correlations between the various indicators of water at 4℃ were generally higher than that at-2℃.Overall,on the side of sensory quality,color difference analysis and volatile components changing,the carp blocks at-2℃ were better than that at 4℃.For the indexes of hardness and springiness,the variation trend of carp blocks at-2℃ were more gentle.However,the differences of the cohesiveness,gummniness and chewiness between-2℃ and 4℃ were small,the moisture migration of carp was more intense during storage at 4℃.3.The pulsed light sterilization technology was used on common carp,and the effects of pulsed light sterilization technology on the extension of common carp shelf life were studied.The better sterilization condition was:pulse energy was 100J and the flash time was 15s,The results showed that the sensory quality,texture index,TVC and TVB-N of carp during storage were all better than that of the control group.It was believed that the shelf life of control group was about 6d and the pulse light sterilization technology could extend the shelf life of refrigerate carp to about 12d. |
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