Experimental Study of Freeze-thaw Cycles Placement in Heat Pump Drying of Tilapia Fillets

Abstract

Freeze-thaw placement in the drying process can reduce the average drying temperature of the sample. In order to speed up the drying process and maintain a good drying quality of dry tilapia fillets which were achieved in the condition of freeze-thaw cycles placement in a heat pump drying process, a series of dryingtests were studied by using the drying time points as the variables in drying process. Freeze-thaw parameters of 4-7 (twice placement) drying time point were optimized by L9(3⁴) orthogonal experiment at 7^th hours of drying. The results showed when freeze-thaw were placed into the process of heat pump drying processwhich could improve the quality of dried tilapia fillets effectively. The best quality indicators under optimal condition were as follows: The value of Ca²⁺-ATPase activity, rehydration rate, whiteness and hardness was2.75 µmol Pi/mg prot/h, 34.32 %, 38.87 and 10.0 N, respectively. The comprehensive score of optimizing process was 99.27. which has been improved 17% compared to the control sample. This result can provide a new low temperature drying technology and a reference for similar aquatic products.