Determination of caffeine in Robusta coffee beans with different roasting method using UV-Vis spectrophotometry

Caffeine is one of the substances in coffee. Several factors affect the caffeine content in coffee, such as harvesting, post-harvesting, roasting, drying, and storage. This study aimed to compare the roasting methods to caffeine content from two samples of robusta coffee beans (from two different areas in east Java, Indonesia) and determine the caffeine using UV-Vis spectrophotometry. Light (180°C), medium (210°C), and dark (240°C) roast profiles were used. This method was validated pertaining to linearity, precision and accuracy studies, limit of detection (LOD) and limit of quantification (LOQ). The result of the validation method showed the specificity of caffeine in coffee with dichloromethane as solvent at a Wavelength of 275 nm. The linearity showed linear results at a concentration of 5-40 ppm. The linear correlation coefficient (r2 ) was 0.9997. The LOD and LOQ were 0.57 ppm and 1.90 ppm, respectively. The accuracy method showed % recovery in the range of 97.9-99.6%. The precision results showed % relative standard deviation of between 0.9-1.0%. The result showed that the highest caffeine content was found in the light roast profile up to 8%. Based on the statistical test, there is no difference in caffeine content between the two samples (p>0.05). In conclusion, the different roasting methods affect the caffeine content (p<0.05). The caffeine content will decrease as the roasting temperature increases. The method was established to be simple, linear, precise, accurate as well as sensitive and can be applied to determining the caffeine content in coffee.