Exploring the Effect of Roasting Degree on the Content of Organic Acids in Coffee Beans Based on UPLC-MS/MS

The influence of roasting degrees of coffee beans on contents of organic acids which directly affect the coffee taste was investigated in this study, using a newly established ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method to measure seven kinds of organic acids. The method showed a good linearity over the range of 0.5～20.0 mg/kg for 7 organic acids with R²>0.990. Recovery rates of 7 organic acids were 81.9%～104.7% at three spiked levels in roasted coffee beans and the relative standard deviations were 0.53%～6.64%. Honduras coffee bean samples results showed that with increasing roasting degree, the contents of malic acid and citric acid decreased gradually, fumaric acid content first increased and then decreased, succinic acid, tartaric acid, shikimic acid as well as quinic acid gradually increased. Light roast had the highest total contents of malic acid and citric acid and lowest content of quinic acid at a concentration of 1201.5 mg/kg and 1363.7 mg/kg, respectively, showing the best taste. Organic acids of coffee beans from Kenya, Indonesia, Brazil and Salvador showed the similar regular changes in the roasting process.