Abstract:The aim of this study was to assess the endogenous stimulating factors of thermal decomposition of trimethylamine-N-oxide (TMAO). The influence of reducing sugar on the thermal conversion of TMAO to formaldehyde (FA), dimethylamine (DMA), and trimethylamine (TMA) in squid was studied using thermal decomposition kinetics. At high temperatures, the TMAO in squid was decomposed into FA, DMA, and TMA, and the content of the reducing sugar was reduced. In vitro screening demonstrated that the additions of seven types of reducing sugars could significantly promote FA production in the supernatant of squid and the TMAO-Fe(II) system. Among them, galactose exhibited the strongest stimulation effect, and a similar promoting effect was observed in the supernatant of squid and the TMAO-Fe(II) system on the decomposition of TMAO into FA, DMA, and TMA. Reaction kinetics of the thermal decomposition of TMAO in TMAO-Fe(II) and TMAO-Fe(II)-Gal were studied comparatively. The changes in the contents of FA, DMA, TMA, and TMAO followed the zero order kinetics. The thermal decomposition of TMAO was divided into two stages, in which the apparent activation energies of stage 2 were lower than those of stage 1. The addition of galactose reduced the activation energies significantly. Therefore, the addition of galactose and other reducing sugars should be limited during the processing of squid products to control the decomposition of TMAO to FA.
