Effect of liquid nitrogen spray freezing on the ice crystal size and quality of large yellow croaker

Large yellow croakers (Larimichthys crocea) were frozen by liquid nitrogen spray freezing (LNSF), liquid immersion freezing (LIF), and air freezing (AF), and the freezing rate, ice crystal size and product qualities were compared. LNSF was found to be a promising freezing technology because of the significantly (P < 0.05) shortest freezing time, smallest ice crystal, and best overall product quality. Then, the effect of processing parameters during LNSF on freezing characteristics, and microstructure and qualities of samples was studied. Freezing time was reduced by decreasing freezing temperature and increasing air velocity. A size uniformity index was proposed in this study to evaluate the distribution uniformity of ice crystals. The minimum cross-sectional area (605.83 μm2) with the best size uniformity was achieved at a freezing temperature of −90 °C, a final temperature of −30 °C, and an air velocity of 4 m/s, showing a reduction of 50.90% as compared to the maximum (1233.77 μm2). The qualities of samples frozen by LNSF with the aforementioned parameter values were well maintained and met the industrial standard. Therefore, the developed LNSF protocol was recommended for the industrial application for large yellow croaker.