This article will discuss the impact of different ways of frozen shrimp center temperature , texture of shrimp , salt-soluble proteins.
Liquid nitrogen can be described in a wide range of aquatic products . Frozen in liquid nitrogen freezing can better maintain the quality of raw materials, due to the extremely low temperature of liquid nitrogen itself , too late to move the water molecules will form a tiny ice crystals , quantity and uniform distribution, greatly reduce the extent of damage to the organizational structure , food thawed basic foods can maintain the original color , smell and taste .
Frozen shrimp way can be broadly divided into three types : frozen in liquid nitrogen , quick-freezing machine ( ammonia refrigeration, fluorine refrigerant ) , common cold . We look at the results were compared to three ways.
Frozen in liquid nitrogen within a few seconds can quickly by 0 ℃ -5 ℃ to generate the maximum ice belt, and quickly deep-frozen vannamei to -18 ℃, the center temperature shrimp declines linearly ; -38 Freezer ℃ (the ammonia refrigeration, fluorine refrigerant ) effect , followed by 0 ℃ to -5 ℃ takes about 18min, quick-frozen to -18 ℃ to shrimp takes about 30min; common cold frozen worst , generated by the largest ice with time is about 24min, and at this stage the temperature drop is very gentle , about 45min to frozen prawns to -18 ℃. By comparing the speed of the three frozen , quick-frozen in liquid nitrogen can be seen in other ways can be achieved quickly frozen shrimp compared .
Impact of the loss of frozen shrimp manner Texture
After a variety of frozen shrimp processing changes the texture is not very obvious. Frozen in liquid nitrogen treatment , in addition to adhesion and chewiness significantly lower than fresh shrimp , the other parameters were not significantly different. After ultra-low temperature of frozen processed only significant differences adhesion, elasticity and chewiness , and fresh shrimp . But after a cold frozen shrimp in addition to the direct adhesion and chewiness was no significant difference with the fresh shrimp , each of the other indicators , there were significant differences. Thus by direct freezing cold shrimp processing quality constructed for greatest impact , most are not suitable for freezing shrimp .
Impact Freezer ( ammonia refrigeration, fluorine refrigerant ) way of shrimp salt-soluble protein content
Fresh shrimp content of salt-soluble protein 127.05mg / g, when handled by the type of frozen shrimp body than the salt-soluble protein content varies greatly , which was frozen in liquid nitrogen after 114.64mg / g, which content and fresh shrimp salt-soluble protein content in vivo minimal difference , but the difference was statistically significant after the analysis found significant differences between the two . After quick-freezing machine ( ammonia refrigeration, refrigeration fluoride ) content shrimp and salt-soluble proteins after cold treatment also significantly lower than frozen in liquid nitrogen treatment groups, respectively 82.01,58.74 mg / g, and also the difference between the two significant. After the description of the different ways of frozen shrimp processing , salt-soluble proteins are different degrees of degeneration , but the relative ratio below , frozen in liquid nitrogen freeze caused by degeneration smaller. From the thermal dynamics that reducing salt soluble protein content is the result of the interaction of the protein interaction with water molecules and protein balance conversion. IQF treatment resulted in a strengthening of the interaction between the protein molecules, and protein interactions with water weakened. Resulting in protein tertiary structure is destroyed , and the precipitation of protein-protein cross-linking occurs , the salt soluble protein content decreased .
Overall, after three kinds of frozen shrimp deal little change in its texture , frozen in liquid nitrogen in which the difference between treatment groups and between small fresh shrimp , frozen in liquid nitrogen and therefore better able to explain to maintain the quality of shrimp structure . Frozen in liquid nitrogen after processing shrimp fresh salt-soluble protein content of less than shrimp , but significantly higher than -38 ℃ freezer ( ammonia refrigeration, fluorine refrigerant ) and -18 ℃ ordinary cold storage of frozen .