- 學位論文
紫米花青素在乙醇溶液中顏色表現之研究
Color Phenomena of Black Rice Anthocyanin in Ethanolic Solutions
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摘要
紫米又稱為黑糯米，營養價值較一般白米高，外觀呈紫黑色，其良好的抗氧化性可能與種皮含有豐富的花青素有關。本研究以紫米為試驗材料，並以紫米花青素萃取液配製模式溶液，利用簡單的模式系統探討紫米花青素在乙醇溶液中的變化，主要在於以反應動力學探討不同乙醇濃度 (10 – 50 %) 及酸鹼值 (1 – 8) 對於花青素穩定性及呈色之影響。期望對於酒精飲料的品質提升與顏色的保存有助益。 實驗結果顯示，紫米花青素於乙醇溶液中之降解屬於一級反應，在 40 oC 及55 oC 時，反應速率常數隨著乙醇濃度提高而減少，而在 25 oC 時則是隨著乙醇濃度提高而增加，其半衰期介於 2.97 – 184 天之間；於 55 oC 環境下，酸鹼值越高花青素降解速率越快，其半衰期介於 6.76 – 100 天之間。 在呈色方面，55 oC 儲藏過程中，不同乙醇濃度及不同酸鹼值的紫米花青素模式溶液皆由紅色向淡黃色轉變，且 Hunter’s L值及 Hunter’s b 值、花青素裂解指數上升，Hunter’s a值及色澤密度下降。 在花青素型態方面，紫米花青素於酸鹼值 1.0下之聚合型態高達 95.70 %，而隨著酸鹼值的提高，聚合型態花青素的比例逐漸減少，單體型態逐漸增加。在總抗氧化能力及 DPPH 自由基清除能力試驗中，紫米花青素 40 % 乙醇模式溶液於酸鹼值 3.0 – 6.0 的抗氧化能力較佳。
並列摘要
Black glutinous rice is also known as black rice. It has higher nutritional value than polished rice. Its dark purple color and anti-oxidative activities are primarily due to the presence of anthocyanin in the bran. This study was to investigate the effect of ethanol concentration and pH value on the stability of black rice anthocyanin and color phenomena in ethanolic model solutions. In the experiments, pH 1 – 8 model solutions of 10 – 50 % ethanol containg black rice anthocyanin were used. The results revealed that the degradation rate of black rice anthocyanin in ethanolic solutions follows apparent first-order kinetics, and the rate constant is decreased with the increase of ethanol concentration at 40 oC and 55 oC but increased at 25 oC. The half-life of anthocyanin degradation in 10 – 50 % ethanolic solutions are between 2.97 – 184 day, respectively. The degradation rate constant is decreased with the increase of pH value at 55 oC and the half-life are between 6.76 – 100 day at 40 % ethanol concentration, respectively. During 55 oC storage of model solutions at different ethanol concentrations and pH values, the degradation index, Hunter’s L and b values increased while a value and color density decreased. In pH 1.0 model solution, polymeric anthocyanin content reached 95.70 %. When the pH value increased, the polymeric anthocyanin content decreased and monomeric anthocyanin increased. The TEAC and DPPH radical scavenging ability of various black rice anthocyanin ethanolic model solutions was highest at pH 3.0 – 6.0.
並列關鍵字
black rice ； anthocyanin ； ethanol ； reaction kinetics ； color phenomena ； antioxidant capacity參考文獻
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