Changes of acid value of lipid, chlorogenic acid content and anti-oxidative activities in roasted coffee for short term storage

Regarding the facts that fat, which is easily oxidized, is one of the major responsible factors affecting the quality of aroma, and polyphenol compounds including chlorogenic acid (CGA) contribute the anti-oxidative activities to coffee, we investigated fat oxidation, conversion of CGA, and changes of anti-oxidative activities according to the degree of roasting and storage of 60 days. We found that the amount of extractable fat by diethyl ether is increased as the coffee beans are roasted longer. Furthermore, the acidity values of the fat are increased from 8.91±0.16 to 17.81±0.11, and 10.37±0.27 to 17.93±0.09 in the medium and dark roasted coffee beans, respectively, while it is increased from 4.47±0.11 to 11.89±0.18 in the green coffee bean after 60 days. The CGA contents in the coffee beans were decreased from 310±8.2 to 282±11.2, then to 58±0.0 mg in 10 gr of the green, medium and dark beans, respectively, and were not changed significantly during the storage period. However, the antioxidative activities measured by 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid radical scavenging assays were not significantly different among the green, medium, and dark coffee beans during the storage period. Furthermore, antioxidant reactive element-luciferase assay showed that biological anti-oxidative activities were increased as coffee beans were more roasted and stored longer. As the total polyphenolic contents in the beans were significantly decreased by roasting, the results suggests that other molecules, such as, Maillard reaction products might play substantial role in antioxidative activity and influence cup quality of coffee.