Abstract:
Acrylamide is a potential harmful compound which can be formed during different food processing methods. The aim of this was to verify the effect of roasting temperature and coffee types on acrylamide formation and the identification of chlorogenic acid, ochratoxin, Caffeine and toxic metals. Four types of coffee (Guji, Jimma, Limu and Sidama) and three roasting temperatures (180, 190,200) ±5 ºC were used for the study. Liquid-chromatographic methods with photo diode detection were used for the analysis of acrylamide, chlorogenic acid and caffeine in roasted ground coffee and inductively coupled plasma mass spectroscopy was used for the analysis of toxic metals. The Calibrations curve for all analysis showed a high correlation coefficient R (>0.999), high sensitivity and reproducibility. In this study Acrylamide content of Guji, Jimma, Limu and Sidama roasted ground coffee were (18623.11±101, 15337.82±274, 19361.56±71 and 21374.89±49.6) μg/kg respectively. The corresponding values for Chlorogenic Acid content (0.80±0.04, 1.49±0.07, 1.13±0.07 and 1.54±0.08) % by mass and the caffeine content (2.23±0.06, 2.18±0.01, 2.24±0.05 and 2.09±0.06) % by mass were obtained respectively. Ochratoxin A was not detected. In this study there was significant difference (p<0.05) on both roasting temperature and coffee type on the formation of acrylamide, chlorogenic acid and caffeine content. As the roasting temperature increased from 180-190oC Acrylamide increased but decreased from 190-200 oC. Chlorogenic acid has negative correlation with the roasting temperature. Caffeine content increased from green coffee to low roasting temperature but decreased at maximum temperature. The color of roasted ground coffee was also affected by roasting temperature and coffee type. The highest L* color value was obtained at 180oC for Sidama Coffee that has higher color value than the others. Toxic metals had a significantly variation among all coffee types and some metals affected by roasting temperature.
Key Words Acrylamide, Caffeine, Chlorogenic Acid, Coffee, roasting temperature