Abstract:
Abstract: Pulsed vacuum takes advantage of the circulatory operation between normal pressure and vacuum pressure. It has been applied to the drying and thawing process of fruits and vegetable. Previous studies have shown that suitable pulsed vacuum pretreatment can effectively improve the drying quality of fruits and vegetables, and is beneficial to the extraction of bioactive substances. However, it is rarely reported about the application of pulsed vacuum pretreatment in fish drying. In order to effectively take the advantages of osmotic dehydration combined with pulsed vacuum effect, this paper attempted to apply pulse vacuum infiltration pretreatment in heat pump drying of tilapia fillet on the basis of osmotic dehydration research. These would break through the limitations of conventional technology and a new process of pulsed vacuum infiltration pretreatment for heat pump drying process of tilapia fillets was obtained. Therefore, in order to obtain the effect of pulsed vacuum impregnation as a pretreatment on the quality of heat pump dried tilapia fillets, whiteness, DEI (dehydration efficiency index), Ca2+-ATPase activity, rehydration rate and texture, as well as the comprehensive scores were evaluated for the quality assessment of tilapia fillets. The relevant evaluation criteria were screened to develop the evaluation factor set according to the test purpose. The weight coefficient of each criterion was determined using the analytic hierarchy process to construct the hierarchical structure models of target layer, factor layer and project layer. A series of single-factor experiments were conducted, and the factors included circulation rate, cycle times, vacuum pressure and trehalose concentration. The results showed: Compared with the control group, the pulse cycle rate could effectively improve the comprehensive quality of the heat pump dried fish fillets, and when the circulation rate was 4:2 within the range of 4:4-5:1, not only the comprehensive score reached the maximum, but also Ca2+-ATPase activity was increased by 42.48%; the cycle number could effectively improve the comprehensive quality of the heat pump dried fish fillets; when the cycle number was 4 within the range of 3-5, the whiteness of fillets got the peak value of 41.08 and increased by 16.98% compared to the control group; the vacuum pressure could effectively improve the comprehensive quality of the heat pump dried fish fillets, and when the vacuum pressure was 10 kPa within the range of 4-16 kPa, the results were better and rehydration rate obtained the balance gradually; when the trehalose concentration was at 130 g/L within the range of 90-170 g/L, the research got the maximum comprehensive score. Moreover, compared with the atmosphere pressure control group, the whiteness, rehydration rate, and Ca2+-ATPase activity of dried tilapia fillets were increased pronouncedly by17.9%, 80%, and 93.6% respectively. By changing the vacuum pressure, vacuum circulation rate, cycle times and the concentration of trehalose, the quality of the heat pump dried tilapia fillets could be promoted with different degrees. Impregnation under pulsed vacuum condition can improve the comprehensive quality of heat pump dried tilapia fillets effectively, which provides a reference for improving the pretreatment process of similar dried products, and also provides technical guidance for similar product technological update.