|Abstract: ||於綠茶湯中添加以醋酐乙醯化法所製備之水溶性幾丁聚醣，探討其抗氧化活性及EGCG含量之儲藏變化。所製備之水溶性幾丁聚醣經高效能液相層析法測得其乙醯化程度為50.26％，稱為半乙醯化幾丁聚醣，並將其以過氧化氫進行降解使其抗氧化活性獲得提升。 添加 5 mg/mL降解後之半乙醯化幾丁聚醣於茶湯中，可增加茶湯清除 DPPH 自由基之能力，在稀釋倍數為40、60 和 120 時，未添加幾丁聚醣之組別其清除能力依序為 67.45、58.61 及 22.37%，添加幾丁聚醣之組別則為 77.41、78.40 和 73.13%；在螯合亞鐵試驗中，添加 0.05 mg/mL 幾丁聚醣之組別螯合能力較未添加者佳。稀釋倍數為 8、16、20 和 32 之茶湯，其螯合能力分別為 46.42、32.66、24.71 及 17.08%，添加幾丁聚醣時則分別提升至 79.57、63.04、61.61 及45.49%。 添加幾丁聚醣能減緩綠茶茶湯儲藏期間 EGCG 下降之現象，且分子量較低之幾丁聚醣之效果較佳。添加未降解之幾丁聚醣於綠茶茶湯中，其 EGCG 之含量於 4oC 儲藏28 天後下降為原來之 53.9%；而添加降解之幾丁聚醣時，其 EGCG 之含量則下降至 62.9%；而控制組則下降至原來之 53.9%。|
Water-soluble chitosan which was prepared by anhydride acetylation method was added to green tea infusions to in investigate the antioxidative activities of the infusions as well as their contents of EGCG during storage. The degeree of acetylation of the prepared water-soluble chitosan was measured by HPLC method and found to be 50.26%. The prepared water-soluble chitosan was named half N-acetylated chitosan. The N-acetylated chitosan was also degraded by oxygen peroxide to improve its antioxidative activity. The scavenging effect of DPPH radical for green tea infusions increased after 5 mg/mL of degraded half N-acetylated chitosan was added to the infusion. The scavenging effect of DPPH radical for green tea infusions which were diluted 40, 60, and 120 folds were originally 67.45, 58.61, and 22.37% respectively. They were found to be 77.41, 78.40, and 73.13%, respectively, when the degraded half N-acetylated chitosan was added. The chelating effect of ferrous ion was also elevated after adding 0.05 mg/mL of degraded half N-acetylated chitosan to the infusion. The chelating effect of ferrous ion for green tea infusions which 8, 16, 20, and 32 folds were originally were 46.42, 32.66, 24.71, and 17.08%, respectively. The effects rasied to 79.57, 63.04, 61.61, and 45.49%, respectively after the chitosan was added. Adding half N-acetylated chitosan alleviated the decrease of EGCG in green tea infusion during storage. Lowering down the molecular weight of the chitosan had a better result. The EGCG contents of green tea infusions, adding with nondegraded and degraded half N-acetylated chitosan, respectively reduced to 53.9 and 62.9% of their original content after 28 days storage at 4℃,while the content of the control decreased to 32.0%.