Quantitative determination of kokumi compounds, γ-glutamyl peptides, in Korean traditional fermented foods, ganjang and doenjang, by LC-MS/MS

Recent studies have shown that γ-glutamyl peptides (GGPs) are recognized by the calcium-sensing receptor and induce kokumi taste. The contents of GGP have been reported in some fermented foods such as cheese and Japanese soy sauce but not in ganjang and doenjang which are representative Korean fermented-soybean products. In this study, the qualitative and quantitative analyses of GGPs in several ganjang and doenjang were carried out by LC-MS/MS using 11 synthetic GGPs as reference compounds. The total GGP contents ranged from 92 to 620 μg/mL for ganjang and from 203 to 387 μg/g for doenjang, respectively. Interestingly, the levels of GGPs were not related to manufacturing types of traditional and industrial products. These data provide a basis for the taste of ganjang and doenjang which was expressed abstractly as mouthful and long-lasting taste.