Effect of Different Freezing Methods on Characteristics of Grass Carp

• 1、State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi 214122, China

Abstract：Effects of immersion freezing on characteristics of grass carp were studied compared with air-blast freezing in this paper. The freezing rate, ice crystals, microstructure and some physicochemical indicators were evaluated to study effects of different freezing methods on quality of grass carp. The results showed that the time through the maximal crystallization zone for grass carp was as follows: air-blast freezing > common packaging immersion freezing > vacuum package-immersion freezing > direct immersion freezing, respectively 23min, 3min, 2.3min, and 2 min. Smaller ice crystals of grass carp were frozen by immersion freezing, causing less damage to muscle fiber and lower thawing loss compared to air-blast freezing. The texture characteristics showed that hardness and elasticity of grass carp frozen by immersion freezing was significantly higher than that of air-blast freezing(P < 0.05). At the same time, ice crystals of grass carp frozen by vacuum package-immersion freezing were slightly larger than those of direct immersion freezing, which had almost the same muscle fiber morphology. There was no significant difference in texture characteristics of grass carp between vacuum package-immersion freezing and direct immersion freezing. Meanwhile, vacuum package-immersion freezing could avoid the odor of alcohol created in direct immersion freezing. Therefore, vacuum package-immersion freezing could better maintain quality of frozen products than air-blast freezing, direct immersion freezing and package-immersion freezing.

Keywords： air-blast freezing immersion freezing vacuum packaging grass carp quality