Effect of some additives on the inhibition of lizardfish trimethylamine-N-oxide demethylase and frozen storage stability of minced flesh

Effects of some additives on the inhibition of trimethylamine-N-oxide demethylase (TMAOase) from lizardfish (Saurida tumbil) muscle were investigated. Sodium citrate and pyrophosphate could inhibit TMAOase activity in a concentration-dependent manner, most likely because of their chelating property. Sodium alginate was the hydrocolloid possessing the inhibitory activity towards TMAOase (P < 0.05). During the storage of lizardfish mince at -20 degrees C for 24 weeks, the addition of 0.5% sodium alginate and 0.3% pyrophosphate in combination with 4% sucrose and 4% sorbitol as the cryoprotectants resulted in the retarded increase in TMAOase activities with the coincidental lowered formation of dimethylamine and formaldehyde (FA), compared with the control (without additives) (P < 0.05). The loss in solubility of muscle proteins was also impeded with the addition of those compounds, suggesting their role in the inhibition of TMAOase as well as the retardation of protein denaturation induced by FA.