Experimental Study on the Influence of Different Loading Weights and Placement Forms on Vacuum Sublimation–Rehydration Thawing of Large Yellow Croaker

To optimize vacuum sublimation-rehydration thawing (VSRT) for batch frozen food, large yellow croakers were chosen as research objects to investigate the influence of different loading weights and placement forms on thawing efficiency, uniformity, effect and energy consumption. The results indicated that varying the loading weight significantly influenced the ice crystal sublimation amount per unit mass of large yellow croakers and the water vapor condensation efficiency. For the system in this paper, the optimal loading weight was 1000 g, which resulted in shorter thawing time (96.25 min), the highest thawing uniformity, the optimal thawing effect and lower total specific energy consumption (SEC) of 2.243 MJ/kg. A loading weight of 2000 g was identified as the maximum for rapid thawing, yielding the shortest specific thawing time (67.83 min/kg). Different placement forms altered the water vapor diffusion path, thereby affecting the condensation efficiency. The application of staggered placement form facilitated faster and more even water vapor diffusion, leading to reduced thawing time (91.75 min), improved thawing uniformity, enhanced thawing effect and lower total SEC (2.185 MJ/kg). Compared with other thawing methods, VSRT exhibited superior performance. Additionally, compared to vacuum steam thawing, the total SEC of VSRT was reduced by 76.17~81.53%.