Use of methylpyrazine ratios to monitor the coffee roasting

Abstract The formation of methylpyrazines has been determined in roasted coffee beans (Arabica and Robusta). The determination of different methylpyrazines was studied by the coupled steam distillation-microdistillator as extraction method and gas chromatography using a capillary column and a thermionic detector. The pyrazine; 2-methyl-; 2,3-dimethyl-; 2,5-dimethyl-; 2,6-dimethyl-; trimethyl- and tetramethyl pyrazine were detected in coffee beans. The principal compound was 2-methylpyrazine. The concentration of the latter pyrazine was more than 2000 μg/100 g of coffee beans depending on the time, the temperature of roasting and the origin of the beans. The correlation of the methylpyrazine quantity with the sensory analysis of the beans has shown the possibility of monitoring the roasting process of coffee beans.