Effects of freeze-thawing pretreatment on heat pump drying quality of tilapia fillets

Author(s): Li Min, Guan Zhi-Qiang, Wu Bao-Chuan

Freeze-thaw is conducive to water exudation and removal, and it may lead to the mutant in organization structure. In order to understand the regular rule of how freeze-thawing pretreatment affects the heat pump drying quality of tilapia fillets, comprehensive experiments of tilapia fillets dried by heat pump were operated with 4 variable factors of freeze-thawing pretreatment consisting of freezing temperature, melting temperature, freezing time and melting time. Moreover, optimal matching was measured by response surface. The result illustrates that compared samples without freeze-thawing pretreatment, those under appropriate freeze-thawing pretreatment would obtain effective improvements of diverse index. Under repeated orthogonal optimization of diverse index, the best condition of freeze-thawing pretreatment that could be obtained is under -32℃ as the freezing temperature, 20℃ as the melting temperature, 1.0h as the freezing time and 87min as the melting time. And under such condition, if the tilapia fillets were dried with 0.30±0.02 moisture content of dry basis for 10 hours, the Ca2+-ATPase activity of dry products of tilapia fillets was 2.35ìmolPi/mgprot/h, and the rehydration rate of that was 37.22%, the rigidity was 9.7N, and the comprehensive grade was 91.191, as a result of which, compared with those samples without freeze-thawing pretreatment, the comprehensive grade ascended by 22.5%. Therefore, the conclusion can provide reference for updating the freeze-thawing pretreatment technology of aquatic products like tilapia fillets

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