Effect of different freezing methods on the ice crystals and quality of white shrimp(Penaeus Vannamei)in the storage

Fresh white Shrimp(Penaeus Vannamei)were stored at -20 ℃ for different period after various frozen treatment including liquid nitrogen freezing,plate freezing and refrigerator freezing. The formation of ice crystals in shrimp meat tissues and changes of the meat quality were analyzed in order to evaluate the optimal way of freeze. Results showed that with the extension of storage time,the content of salt-soluble protein and water holding ability and sensory score decreased significantly(p<0.05)in both plate freezing and freezer frozen groups. The ice crystals formed during liquid nitrogen freezing were tinier 1/3 than plate freezing and tinier 1/2 than freezer frozen. After stored for 180 d,the value of TVB-N was ≤25 mg/100 g.The value of TBA was only 0.72 mg/100 g,suggesting the samples treated by liquid nitrogen was in a relative fresh condition because it could maintain the morphology of tissue better. Liquid nitrogen freezing inhibited the protein denaturation and fat oxidation in shrimp effectively in order to prolonging the shelf life more than 180 d and better quality of the shrimp.