Pacific whiting frozen fillets as affected by postharvest processing and storage conditions.

Whole fish and H&G (headed and gutted) fish were stored under refrigeration (<4 °C) for 0, 2, and 5 days and subsequently filleted and frozen at -18 °C and -80 °C. Frozen fillets were analyzed during 24 weeks of storage. The activity of trimethylamine-N-oxide demethylase (TMAOase) decreased more quickly at -18 °C than -80 °C. TMAOase reduction was distinctively noted at -18 °C storage. Formaldehyde (FA) induced by TMAOase increased at all treatments at -18 °C as frozen storage extended to 24 weeks, but it was near zero at -80 °C up to 12 weeks of storage. Textural toughening, low water retention ability, and low salt soluble protein resulted from the denaturation function of FA. A sudden decrease in surface hydrophobicity at 24 weeks, when stored at -18 °C, resulted from FA-induced unfolding and subsequent aggregation. FA concentration appeared to affect protein aggregations and textual toughening of fillets during frozen storage.