Effect of pre-chilling time on the physicochemical properties of channel catfish during frozen storage

The objective of this study was to investigate pre-chilling time (1, 8 and 24 h) on the changes of channel catfish's physicochemical properties during frozen storage (1, 4, 8, 12 and 24 weeks). During the pre-chilling process, onset and full rigor mortis of the catfish were reached at 1 h and 8 h post mortem. Light microscopy observation showed that gaps among the muscle cells of the catfish increased gradually with the pre-chilling time. Shear force of the catfish fillet with 1 h of pre-chilling (P1 fillet) continuously declined (P < 0.05) during the frozen storage, while shear forces of the catfish fillet with 8 and 24 h of pre-chilling (P8 and P24 fillet) increased with the storage duration up to 8 weeks and then decreased (P < 0.05). With the storage duration increasing, whiteness, expressible moisture and pH of all the fillet samples climbed up and then declined, while contents of TVB-N (total volatile nitrogen) and TBA (thiobarbituric acid) continuously increased (P < 0.05). As for the P1, P8 and P24 fillets, the maximum whiteness values were obtained after storing for 8, 8 and 4 weeks, respectively, and expressible moisture values for 12, 12 and 8 weeks, respectively. Under the same storage duration, P8 fillet showed the relatively higher shear force and lower expressible moisture; TVB-N and TBA contents were significantly higher for the fillets subjected to longer pre-chilling time. (C) 2020 Elsevier Ltd and IIR. All rights reserved.