Effects of freezing method on water distribution, microstructure, and taste active compounds of frozen channel catfish (Ictalurus punctatus)

Abstract Effects of freezing method and frozen storage duration (16 weeks) at −18 °C on water distribution, microstructure, and taste active compounds of channel catfish fillets were investigated. Results showed that freezing and frozen storage resulted in increase in thawing loss, extracellular space, and loss of some taste active free amino acids and inosine monophosphate (IMP). After 16 weeks of storage, the total content of free amino acids decreased to 77.68% (static air freezing), 78.92% (air‐blast freezing), and 83.13% (liquid nitrogen immersion freezing) of their initial value, while IMP decreased by 45.06% (static air freezing), 25.08% (air‐blast freezing), and 24.11% (liquid nitrogen immersion freezing), respectively. Low‐field 1 H NMR T 2 relaxation data showed an increase in relaxation time of T 21 and T 22 , and a decrease of T 21 population with concomitant increase in T 22 population during frozen storage. Compared with the other two freezing methods, liquid nitrogen immersion frozen fillets with rapid freezing rate showed a less alteration of quality, exhibiting more compact fiber arrangements, less thawing loss and better retention of taste active compounds. Practical applications Frozen storage has been widely used to preserve meat products for a long time, but it inevitably caused undesirable physical, chemical, and structural changes, thus leading to quality loss in texture, flavor, and color. And the degree of quality deterioration of frozen food varies depending on materials, freezing process, and frozen storage conditions. Frozen fillet is one of the main processed fish products. The study of the influence of freezing method and frozen storage on the quality of fillets in terms of water distribution, structural changes, and taste active compounds is of importance to better control the quality of frozen fish products in the industry.