Experimental study on the effect of symmetrical heat source on vacuum sublimation-rehydration thawing of large yellow croaker (Larimichthys crocea)

Abstract

For vacuum sublimation-rehydration thawing (VSRT), a novel efficient thawing method, the heat source is one of the main factors influencing its heat and mass transfer. The conventional single-sided heat source is prone to localized overheating, which negatively affects the thawing effect. To improve the thawing process, this paper proposed the application of a symmetrical heat source in VSRT, utilizing radiant heating to improve the thawing efficiency. In this study, the large yellow croaker (-18 ℃ and 260 g) was selected as the experimental object. The effects of heating-plate-to-frozen-food distance (D_H-F) and heating plate temperature on thawing efficiency and thawing effect were investigated. The results showed that under different conditions of heating plate temperatures and D_H-F values, significant variations in thawing efficiency and thawing effect were observed. The optimal operation condition was obtained at both D_H-F of 80 mm and heating plate temperature of 35 ℃. Under this operation condition, the fastest thawing rate (3.48 cm/h), the lowest thawing loss (1.15 %), the optimal color, the minimal change in pH, and lower specific energy consumption (7.420 MJ/kg) were achieved. Compared with air thawing, vacuum steam thawing, and VSRT (single-sided heating), the VSRT (double-sided heating) demonstrated superior performance, reducing thawing time by 70.90 %, 7.97 %, and 7.24 %, respectively, while achieving optimal thawing effect and the lowest energy consumption. These findings demonstrate the advantages of symmetrical heat source in improving VSRT and may provide valuable insights for optimizing VSRT systems in food industry applications.