The Research On The Quality And T.T.-T. Of Grass Carp During Frozen Storage.

This paper is researched the change of the physical,chemical,texture analysis and sensory quality of grass carp deal with two different ways （one group dealed with ice-coating and another group deal without ice-coating） and frozen in four different temperatures. Then do kinetic analysis of chemical quality and texture analysis. Then deduced the shelf-life of two groups of the frozen grass carp which in different storage temperatures by the Arrhenius equation and Q₁₀ function. At last,drawing the T.T.-T. curves of the two groups by the theory of T.T.-T.The grass carp which were refrigerated for 360 days in 255K（-18℃）,248K（-25℃）,243K（-30℃） and 193K（-80℃） used as samples. In order to seek the influence of temperature and time to the shelf-life,the pH,the content of moisture, ash,crude fat and TVB-N value were used to be physical and chemical specifications and do TPA texture analysis. The criterion of sensory evaluation was set as some reference material.It was concluded that,both the two groups of grass carp in the same storage time,the lower the temperature make the better quality of the frozen grass carp. The shelf-life of grass carp without ice-coating which frozen in 255K is 261.5 days, and the shelf-life of grass carp without ice-coating which frozen in 248K and 243K are 377.5 days and 510 days, but the shelf-life of grass carp without ice-coating which frozen in 193K can prolong to 1206.1 days. Compared with the shelf-life of grass carp without ice-coating, the shelf-life of grass carp with ice-coating are 275.4, 498.5 517.8 and 1263.9 days. We can see that do ice-coating has a significant role to prolong grass carp’s shelf-life.The deduction as follows can be obtained from the analysis of the experiment data by the chemical kinetics of quality:the chemical kinetics of quality with time fit the zero order kinetics , expressed by ln（[ A] /[A₀]）= -k1.t,except the pH whose kinetics fit the second order kinetics,expressed by Y = Constant+k₁×t+k₂^t2.For data reduction,use factor analysis to identify a smaller number of factors that can explain the most of the variance observed in a much larger number of manifest variables,so it is used to reduce the data of analysis of physical and chemical. Then the factors got could be used in correspondence analysis with data of TPA texture analysis. Using the factor analysis,in a 95% confidence, the physical and chemical data of the two groups of grass carp which frozen in 255K,248K,243K and 193K can be replaced by two factors,which reflect the 90% information upwards of all. Like what the TPA texture analysis data of the two groups of grass carp frozen in 255K,248K,243K and 193K,the 84% information upwards can be replaced by two factors. Then in the following correspondence analysis in distance analysis , the correspondence between the factor named F1 reflected the information of physical and chemical quality with the factor reflected the TPA texture analysis data is perfect.The shelf-life of the two groups of grass carp frozen in different temperatures could be deduced by the Arrhenius equation and Q₁₀ function. Then,the T.T.-T. curve which based on the T.T.-T. theory was designed.The total results show that:in order to preserve the frozen food and prolong their consume time,they must be circulated in the much lower temperature. The cold chain must be established in the whole circulated link from storage,transportation,wholesale and sale to the consumer. And the continuous handle in the low temperature is necessary.