Determination of glyoxal and methylglyoxal in Thai fish sauce and their changes during storage test

Recently more research attention has been given to glyoxal (GO) and methylglyoxal (MG) in relevant to their role in biological and food systems. In this study, pre-column derivatization using 5,6-diamino-2,4-hydroxypyrimidine sulfate (DDP) for fluorescence detection on HPLC was optimized for fish sauce matrix. DDP–GO and DDP–MG derivatives detected had fluorimetric wavelengths coincided with the spectral characteristics reported. Standard addition experiment showed that the detection method was free from interference and matrix effect with good recovery (90–115 %) and precision (less than 8 % RSD at 88–242 ng/mL). Limit of detection for GO and MG were 11.7 and 10.9 ng/mL respectively. Prolonged storage of the fish sauce sample under 4, 25, 40, and 60 °C showed that GO increased at 40 and 60 °C while MG increased at 25, 40, and 60 °C. The results also suggested possible role of molecular oxygen in these formations. Together with GO and MO, browning development and Strecker aldehydes were also monitored.