| Effects of freezing process and frozen storage on the quality of pork muscle was studied in the paper, in order to find out the relationship between changes of ice crystal in muscle structure and physicochemical and biological properties of muscle. Four main parts were included here: Firstly, effect of freezing temperature on quality of pork muscle; Secondly, effect of temperature fluctuation of quality of pork muscle; Third, effect of freeze-thaw cycle on quality of pork muscle; Fourth, effect of long term storage on quality of pork muscle.Results were listed below:Chapter I Effect of Freezing temperature on ice crystal conformation, Physicochemical and biological properties of pork M.Longissimus dorsi muscle in block and slice shapes were studied in this chapter. Results showed that, integrity muscle fibers were observed in fresh chilled pork and equivalent diameter of the fibers is 45.4~51.4μm. After freezing, structure of muscle was destroyed totally with large ice crystals between the muscle fibers. Equivalent diameters of ice crystal are 135-365μ m for muscle block and 73.12~81.44 μ m for small round slice. Muscle origin had no effect on the test. While freezing temperature had decreasing effect on the L* value and increasing effect on shear value of the muscles. Compared to fresh muscle, pH did not change, water holding capacity decreased, muscle protein solubility decreased, sulphydryl content increased, emulsifying activity index and emulsifying stability did not change significantly (p>0.05).Chapter II Effect of temperature fluctuation on the quality of pork muscle during frozen storage was studied in this chapter. Results showed that: quality of pork changed more and larger ice crystal came into being with more temperature fluctuation. Equivalent diameter is smallest in -10°C(21days) sample which is 67.20 μm; and largest(86.32 μm) in -20℃~-10℃~-20℃ sample. There were no significantly effect on color(L~*,a~*,b~*,C~*, H° ),water loss, TBARS,EAI and ES(p>0.05).While protein solubility and sulphydryl content changed differently. TVB-N increased with more temperature fluctuation.:Chapter III Effect of freeze-thaw cycle on quality of pork muscle was studied in this chapter. Results showed that: quality loss of pork muscle increased when the freeze-thaw cycle times increased. L*,a*,b*,C*,H℃ and pH increased significantly(p<0.05).Thaw drip increased with less water loss and less water holding capacity. Total protein solubility, sacoplasma protein solubility and myofibrilla protein solubility increased with more freeze-thaw cycle times. EAI decreased first and increased after the fourth cycle, while ES increased first and decreased after the fourth cycle. TVB-N number increased gradually. And active sulphydryl content and TBARS did not change significantly (p>0.05).Chapter IV Effect of storage on quality of pork muscle was studied in this chapter. Conformation of ice crystal in frozen samples(without storage) were 4045.855 —5509.739 μ m~2(area) and 69.381-81.439 n m(equivalent diameter).After 150 days storage, the size of ice crystal became larger with 7546.855-11273.890μ m~2(area) and 98.945-115.836 μ m(equivalent diameter). But roundness and elongation of ice crystal did not change significantly(p>0.05).During storage, L*,a* values decreased; b*,H° value increased; while C* value did not change. Also pH and water loss under pressure did not change significantly (p>0.05). Solubility of proteins decreased and active sulphydryl content increased. EAI increased first and decreased. Changes of ES were not the same to different treatment. TVB-N and TBARS value increased with storage, and showed a good relationship with storage time.Generally, freezing and frozen storage had significant effect on quality of pork music. Accordingly, It is necessary to decrease freezing temperature to reduce mechanism deterioration. And sharp temperature fluctuation should be avoided during long term storage to decrease quality loss.
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