| Summary: | 碩士 === 輔仁大學 === 食品營養學系 === 87 === Light-roasted, medium-roasted and dark-roasted coffees from Brazil, Colombia, Mandehling, Panama, Indonesia and Thailand were used to study the inhibition of superoxide anion radicals produced in xanthine/xanthine oxidase system. Different regional coffees, degree of roasting and their interaction significantly (p<0.05) influenced the inhibition of xanthine oxidase activity. Chlorogenic acid, caffeic acid and caffeine were able to inhibit xanthine oxidase activity. After heating at 205℃, 215℃ and 225℃ for 15 min, the three compounds reduced their inhibition ability with increasing temperature.
The influence of Brazilian, Colombian, Mandehling and Thai coffees with three degrees of roasting on removing hydroxyl radicals was also investigated. Different regional coffees, degree of roasting and their interaction were significant on scavenging radicals (p<0.05). Light-roasted Brazilian and Colombian coffees, medium-roasted Mandehling and dark- roasted Thai coffees showed better removing abilities. Both roasted and ground coffees packed in aluminum-foil bag had the same effect on the removal of hydroxyl radicals during 14-day storage. The scavenging ability was greatly influenced by storage time rather than storage temperature. Pure chemicals of chlorogenic acid, caffeic acid and caffeine showed strong abilities to scavenge radicals. However, after heating at 205℃,215℃ and 225℃ for 15 min, chlorogenic acid and caffeic acid became prooxidant and caffeine decreased scavenging ability. Storage conditions had no effect on the properties of heated chlorogenic acid. Compared to temperature, storage time of caffeic acid and caffeine had greater effect on the scavenging ability.
The inhibition abilities of linoleic acid ethyl ester (LAEE) oxidation by the above four coffees with three degrees of roasting were significantly different (p<0.05). All light-roasted coffees showed strong antioxidant activities and followed by medium-roasted and dark-roasted. Both roasted and ground coffees packed in aluminum-foil bag had the same antioxidant activities during 14-day storage. Storage time showed greater effect than temperature on antioxidant activity. Pure chemicals of chlorogenic acid, caffeic acid and caffeine had ability against LAEE peroxidation. After heating at 205℃,215℃ and 225℃ for 15 min, chlorogenic acid and caffeic acid increased antioxidant activity, whereas caffeine decreased. Storage of these heated compounds at 4℃and 25℃ had no effect on their antioxidant abilities. However, the antioxidant ability of chlorogenic acid and caffeic acid increased after 7- and 14-day storage, and that of caffeine decreased with time.
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