The Analysis of Chlorogenic Acid and Caffeine Content and Its Correlation with Coffee Bean Color under Different Roasting Degree and Sources of Coffee (Coffea arabica Typica)

Abstract

Coffee is one of the main economic crops in the world and is now widely grown throughout Taiwan. The process of roasting coffee begins with the heating and smooth expansion of raw beans, which leads to changes in appearance and color while affecting the flavor and taste of coffee. So far, most coffee manufacturers have used visual inspection or colorimeter methods to identify differences in coffee quality. Moreover, there is no literature discussing the correlation of roasted bean color with caffeine and chlorogenic acid content. Therefore, the purpose of this experiment was to analyze the chlorogenic acid and caffeine content and their correlation with bean color under different roasting degrees and from different sources to establish basic data for the rapid identification of coffee quality in the future. In this experiment, the coffee Coffea arabica typica from Dongshan, Gukeng, and Sumatra’s Indonesian rainforest was used, and the beans were roasted into four degrees: raw bean, light, medium, and dark roast, to investigate the appearance of the coffee beans and its correlation with caffeine and chlorogenic acid content. The results showed that with a higher roasting degree, caffeine content increased gradually, except for Indonesian beans, but the chlorogenic acid content in all samples showed a declining trend with the increase in roasting degree. The correlation between the chlorogenic acid content and the color space value of the coffee bean color shows that L*, a*, and h° in both ground and unground coffee are highly correlated. The C* value of the ground and unground coffee showed a correlation coefficient of r = 0.159 ns and 0.299 ns, respectively. The correlation between the caffeine content and the color space value of the unground coffee bean shows that the a*, b*, and C* value is highly correlated with the caffeine content. The color space values of ground coffee beans show no correlation with caffeine.

Effects of Different Processing Methods of Coffee Arabica on Colour, Acrylamide, Caffeine, Chlorogenic Acid, and Polyphenol Content

“…No significant relationship between CQA content and colour characteristics was found in the present study, contrary to the results of Tsai and Jioe [ 20 ], who reported a strong correlation between CQA × L* and CQA × a*, respectively.…”

“…Irrespective of the above-mentioned differences, caffeine content reported by Król et al [ 24 ] was substantially lower in comparison with our data (12–13 mg g −1 , Table 1 ). A slightly higher caffeine content in dark-roasted as compared to light-roasted coffee was reported Tsai and Jioe [ 20 ].…”

“…Moreover, Mills et al [ 36 ] found out that the greater the degree to which the coffee has been roasted, the lower the content of CQA. Similarly, Tsai and Jioe [ 20 ] reported a decrease in CQA after roasting and the lowest content was reached in dark-roasted coffee samples. We can only partially confirm these findings [ 27 , 30 ]: when calculated irrespective of the production method, medium roasting significantly decreased CQA content in comparison with light roasting in the present study, but a manifestation of the dark roasting was less conspicuous.…”

“…According to Tsai and Jioe [ 20 ], the dry fermentation method turns the raw coffee beans from white to brown, while the wet fermentation method turns them from blue to green. Based on the results of the present study ( Table 3 ), the dry-processed, dark-roasted coffees, compared to wet-processed, dark-roasted samples, had higher both the a*-value and the b*-value (stronger transition from red to green and from yellow to blue, respectively).…”

“…There exists not much literature dealing with the correlation between coffee ground colour and caffeine, CQA, and TPP content. Tsai and Jioe [ 20 ] found a high correlation between the L* parameter (lightness), resp. a* parameter (the colour space between green and red), and the CQA content of ground coffee.…”