Analysis of alpha-dicarbonyl compounds and 4-methylimidazole in coffee made with various roasting and brewing conditions

Abstract

In this study, the 4-methylimidazole (4-MI) and alpha-dicarbonyl compounds (alpha-DC), including glyoxal, methylglyoxal (MGO), and diacetyl (DA), formed in coffee made using various roasting and brewing methods was analyzed. In 72 espresso coffee samples made using Coffea arabica from Brazil and Ethiopia and C. robusta from India and Vietnam, the levels of total alpha-DC and 4-MI ranged from 10.3 to 90.4 mu g/L and 11.7-135.9 mu g/L, respectively. The level of alpha-DC was higher in C. arabica (60.4 mg/L) than in C. robusta (32.1 mg/L). C. robusta (67.5 mg/L) had higher levels of 4-MI than C. arabica (60.0 mg/L). As roasting temperature and time increased, the levels of MGO, DA, and 4-MI significantly increased (p < 0.05). In the espresso method, using smaller coffee bean particles led to significantly higher concentrations of alpha-DC and 4-MI (p < 0.05). In the cold brew method, the highest concentrations of alpha-DC and 4-MI were found with the largest coffee bean particles (p < 0.05).