Analysis of glyoxal, methylglyoxal and diacetyl in soy sauce

In this study, an analytical method for the determination of α-dicarbonyl compounds (α-DCs), including glyoxal (GO), methylglyoxal (MGO) and diacetyl (DA), in soy sauce was validated using gas chromatography-nitrogen-phosphorus detection. Through Maillard reaction various α-DCs, including GO, MGO and DA have been found in fermented food, dairy products and beverages. The analysis of α-DC was carried out by a derivatisation with o-phenylenediamine. The limit of detection and limit of quantitation were 0.04 and 0.12 μg/kg for GO, 0.04 and 0.13 μg/kg for MGO, and 0.07 and 0.22 μg/kg for DA. The intra- and inter-day accuracy ranged from 92.8 to 109% for GO, from 99.5 to 113% for MGO and from 93.6 to 102% for DA. The intra- and inter-day precision ranged from 3.38 to 12.1% for GO, from 0.67 to 7.65% for MGO and from 1.27 to 9.35% for DA. In 20 commercial soy sauces, α-DCs were found in concentration ranges of 5.60-31.7 μg/mL for GO, 14.4-116 μg/mL for MGO and 0.47-5.48 μg/mL for DA. The developed analytical method could be applied for the determination of α-DCs in soy sauce and motivate investigations related to reducing the content of α-DCs in soy sauce.