Microstructure and physicochemical properties: Effect of pre-chilling and storage time on the quality of Channel catfish during frozen storage

The objective this research was to investigate pre-chilling time (1, 4, 8 and 24 h) on the histomorphology and physicochemical properties of catfish fillets during frozen storage (1, 4, 12 and 24 weeks). With the extended pre-chilling (4 °C) and frozen storage (−18 °C) time, cells of catfish fillet were gradually dissociated in three aspects: size change, dispersion and breakage by ice crystals. Catfish fillets pre-chilled for 24 h or stored for more than 12 weeks showed apparent higher cell structure damage than other treated groups. The Magnetic resonance imaging (MRI) results showed that the activity of hydrogen protons was progressively enhanced with the storage time up to the 4 weeks and then decreased. With the increasing frozen storage period, pH of catfish samples were transferred from weakly alkali to weakly acid, shear force and whiteness of frozen channel catfish fillets was progressively decreased (P < 0.05), while the total volatile base-nitrogen (TVB-N), K value, expressible moisture and thiobarbituric acid-reactivate substance (TBARS) contents were increased (P < 0.05). Therefore, the maximum pre-chilling time and shelf-life of frozen catfish fillets should be recommended as 8 h and 12 weeks, respectively. This research provided theoretical support for aquatic processing industrially.