Effects of Different Freezing Methods on the Quality of Oyster

The effects of freezing methods including immersion freezing,air blast freezing and static freezing,on the quality of oysters were studied by the indexes of freezing curve,freezing rate,water holding capacity,protein denaturation,color and texture. Results showed that the freezing rate of immersion freezing was 6.67 cm/h,which was 5 times that of air blast freezing and 23 times that of static freezing. Moreover,there were the least of drip loss and cooking loss for the oysters treated with immersion freezing,6.75%±1.12% and 42.08%±3.72% respectively. Furthermore,with(48.15±5.53) mg/g of salt-soluble protein contents and(0.202±0.020) μmol Pi/(mg·h)of Ca²⁺-ATPase activity,it also had the lowest degree of protein denaturation. The elasticity of immersion freezing oysters was(3.96±0.25) mm,which was significant difference(p<0.05)compared with the oysters treated with air blast freezing and static freezing. However,there were no significant difference(p>0.05)on color(L^*,a^*,b^*,ΔE),hardness and chewiness between different freezing methods. There was no significant difference between fresh and immersion freezing oysters(p>0.05),but there were significant difference in salt-soluble protein contents,Ca²⁺-ATPase activity and elasticity between fresh and air blast freezing or static freezing oysters(p<0.05). Collectively,immersion freezing had the advantages over air blast freezing and static freezing in maintaining the quality of oyster,and which was closer to fresh oysters.