Effect of rapid freezing technology on quality changes of freshwater fish during frozen storage

The impacts of pre-frozen with −80 °C liquid nitrogen spray freezer (LNF), −80 °C refrigerator freezer (RF), and −30 °C micro-freezer (MF) on the freezing rate, physical and chemical properties and microscopic structures of freshwater fish (grass carp, tilapia and bighead carp) stored at −18 °C (14 days) were evaluated. LNF and MF were effective in shortening the entire freezing period and their muscle tissue microscopic structures were more homogeneous and thicker than the RF group, also with smaller and more regular ice crystal. Additionally, the LNF-treated samples had good water holding capacity and textural characteristics and significantly delayed changes in immobilized water content, effectively suppressing the increase in L* values in grass carp samples (p < 0.05). However, MF was not as effective as LNF and RF in inhibiting the formation of TBARS and TVBN. In conclusion, LNF played a more positive role in quality retention of freshwater fish.