| Summary: | 碩士 === 輔仁大學 === 食品營養學系 === 91 === The antioxidant capacity of cold and hot brewed coffees prepared from medium- and dark-roasted Brazil and Mandheling coffee beans was studied. The effect of additions of coffee whitener and milk products to brewed coffee and the difference in antioxidant properties between the freshly brewed and canned coffees were then evaluated. Finally, the changes of antioxidant effect of canned coffee keeping at 60℃－80℃ during 48 hours were also investigated.
Hot and cold coffees prepared from medium- and dark-roasted Brazil and Mandheling coffee beans did not show any significant difference (p＞0.05) in the ability to inhibit the formation of superoxide anion radicals mediated by the xanthine/xanthine oxidase system, and the ability to scavenge the α, α — diphenyl — β — picrylhydrazyl (DPPH•) radical. There was also no obvious difference in TAS. The coffee whitener and milk products showed antioxidant activities, with the highest for whole milk and followed by low-fat milk, skimmed milk, and coffee whitener. However, the addition of coffee whitener and milk products significantly reduced the inhibition of the xanthine oxidase activity. Additions of milk products did not decrease the TAS and the DPPH• radical scavenging ability of brewed coffee. The antioxidant activity of brewed coffee with whole milk addition was higher than that with skimmed milk, whereas addition of coffee whitener significantly decreased the antioxidant effect of brewed coffee (p＜0.05).
Canned coffee prepared from medium-roasted Brazil and dark-roasted Mandheling brewed coffees reduced antioxidant activities significantly (p＜0.05) compared to the brewed coffee before canning when xanthine/xanthine oxidase and the DPPH• radical systems were evaluated. The antioxidant activity of canned coffee remained nearly constant during four weeks of storage.
Holding canned coffee at 60℃, 70℃, and 80 °C for 48 hours did not change the antioxidant properties of both xanthine/xanthine oxidase and the DPPH• radical systems. Similarly, there were no significant differences(p＞0.05) in the antioxidant effect among canned coffee samples that were held at different temperatures for the same period of time.
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