EFFECTS OF TRIMETHYLAMINE-N-OXIDE DEMETHYLASE (TMAOase) INHIBITORS AND ANTIOXIDANTS ON PHYSICOCHEMICAL AND BIOCHEMICAL CHANGES OF HADDOCK MUSCLE INDUCED BY LIZARDFISH TMAOase DURING FROZEN STORAGE

The addition of trimethylamine-N-oxide demethylase (TMAOase) inhibitor (0.3% pyrophosphate and 0.5% alginate) in haddock mince containing TMAOase retarded the formaldehyde (FA) formation throughout the storage at −10C for 6 weeks (P < 0.05). On the other hand, antioxidants (250 mg ascorbic acid/kg and 250 mg tocopherol/kg) induced FA formation. Proton nuclear magnetic resonance (1H NMR) spectroscopic study revealed that dimethylamine was formed in the mince with added TMAOase with a concomitant decrease in trimethylamine oxide (TMAO) content. Antioxidants had a significant effect on the inhibition of lipid oxidation. The loss of protein solubility increased as the result of FA formation, which was associated with the increased aggregation of proteins as evidenced by the increases in final storage modulus (G′) and loss modulus (G″) (P < 0.05). TMAOase inhibitors lowered G′ and G″ of mince containing TMAOase. TMAOase inhibitors, together with antioxidants, decreased the protein denaturation induced by both FA and lipid oxidation. PRACTICAL APPLICATIONS Use of pyrophosphate in combination with alginate at the appropriate amounts into fish mince was a promising means to retard the formation of formaldehyde induced by trimethylamine-N-oxide demethylase. As a consequence, the losses in properties of fish mince could be retarded during the extended frozen storage and the losses in market value could also be reduced.