Contribution of mozambioside roasting products to coffee's bitter taste

Roasting degrades the coffee compound mozambioside (1) into several products, including 17-O-β-D-glucosyl-11-hydroxycafestol-2-one (2), 11-O-β-D-glucosyl-16-desoxycafestol-2-one (3), 11-O-β-D-glucosyl-(S)-16-desoxy-17-oxocafestol-2-one (4), 11-O-β-D-glucosyl-15,16-dehydrocafestol-2-one (5), 11-O-β-D-glucosyl-(R)-16-desoxy-17-oxocafestol-2-one (6), bengalensol (7), and 11-hydroxycafestol-2-one (8). A UHPLC-MS/MS method was established to quantify 1-8 and monitor their formation during authentic coffee roasting. Concentrations of 1 and the dominant roasting products 4, 5, and 7 ranged from 21.0 to 170.4 nmol/g in coffee powders, with ∼41-128 % extracted into the brew. Human bitter taste thresholds of 1, 2, and 4-8 were determined. The major roasting products exhibited lower thresholds (27-80 μM) than 1 (132 μM). Genotyping of panelists revealed a correlation between sensitivity for mozambioside-derivatives and the presence of intact TAS2R43 gene loci. The combination of 1-8 in coffee concentrations elicited a bitter taste recognized in 80 % of the panelists, suggesting this compound class contributes to coffee's taste profile.