此研究目的為鑑定澎湖仙人掌果汁色素之結構，與分析其安定性以應用在加工應用上，並發展毛細管電泳方法以分離仙人掌果汁色素。 在色素構造之鑑定方面：以分析型HPLC測定仙人掌果汁色素，移動相以CH3OH: KH2PO4(50mM，pH2.75)比例為18:82的條件下測定，發現與紅甜菜色素相似，且經過共注射有相同的滯留時間(retention time)；以分析型HPLC測定，使用具有專一性的β-glucosidase 酵素水解仙人掌果汁色素，水解前主要為betanin及isobetanin，水解後，色素主要為betanidin及isobetanidin。而betanin水解後為betanidin，isobetanin水解後為isobetanidin。以質譜儀(FAB- Mass)測定仙人掌果汁色素第一帶及第二帶，再以質譜串聯法(Mass-Mass)做進一步鑑定，在551 Da/e有明顯分子離子峰及389 Da/e有明顯的斷裂峰，第一帶主要結構為含glucose的betanin，第二帶主要結構為含glucose的isobetanin；利用毛細管電泳測定時，仙人掌果色素以偵測長度60cm，全長為67cm長的毛細管分離，電解緩衝液(running buffer)為 10mM Citrate-K2HPO4 buffer (pH6.0)內含6mM DTAB (Dodecyltrimethyl-ammonium bromide)及4mM CaCl2，應用電壓為-20kV，電動注射時間1秒鐘，在室溫(25℃)的條件下，可測得仙人掌果汁色素與紅甜菜色素有相同的滯留時間(migration time)，能進一步鑑定仙人掌果汁色素為具有相同betanin與isobetanin成份。 在安定度分析方面：仙人掌果汁色素為水溶性色素。此色素在pH值2~8時為紫紅色，適用的食品著色酸鹼範圍廣，呈色值較安定，遠較花青素可應用的範圍更為廣泛。仙人掌果汁色素中betanin與isobetanin為兩主要色素，兩者可見光之吸收光譜類似，皆呈紫紅色。仙人掌果汁色素對酸鹼安定性：pH5、pH4>pH6、pH3>pH7、pH2，而在強酸及中性下，較不安定。仙人掌果汁色素，在pH3、pH5及pH7下，不同溫度的熱安定度：25℃>60℃>80℃>95℃。此色素對熱敏感，在最適pH時，80℃、95℃下的半衰期分別為30分鐘、10分鐘；對於熱加工食品，須在很短時間內完成加熱殺菌，以保持固定的色澤。空氣對此色素的影響只有些微差異，光線對此色素安定度影響較大。故存放此樣品時，以不透光容器較佳。以β-glucosidase水解，在水解20 min時，isobetanin水解90％，而betanin水解25%，故betanin遠較isobetanin安定。 Two major pigment in Opuntia dillenii fruit juice were found to be beta-cyanin and had identical retention time to betanin and isobetanin from Beta vulgaris in analytic HPLC condition. Both pigments were subject toβ-gluco-sidase hydrolysis and were converted into betanidin and isobetanidin. By using FAB-mass, both pigments showed molecular ion of 551 Da/e and fragment ion of 389 Da/e, identical to betanin and its hydrolyzed product, betanidin respec-tively. Separation of pigments was also achieved by reversed electroosmotic flow capillary electrophoresis in the presence of 4 mM Ca++. Pigments from Opuntia dillenii were found to have identical migration time to those of betanin and isobetanin from Beta vulgaris. Results from experiments above indicated that two major pigment in Opuntia dillenii fruit were betanin and isobetanin. Opuntia dillenii fruit juice pigments are water-soluble pigment. It is purple red between pH2~8. Two major pigments in Opuntia dillenii fruit juice, betanin and isobetanin, are similar in visible absorption spectrum, and in color of purple red. The stability of juice pigment at different pH value are in following order: pH5、pH4>pH6、pH3>pH7、pH2. Its thermal stability order is 25℃>60℃>80℃>95℃. At optimal pH, half life of the pigment at 80℃ and 95℃ is 30 min and 10 min respectively. Therefore heat processing of the juice should be finished in short time to minimize the thermal degration of pigment. Air showed little effect on storage stability. Whereas light exhibited some detrimental to stability. Betanin exhi-bited more resistant than isobetanin toβ-glucosidase hydrolysis. The degree of betanin and isobetanin hydrolysis byβ-glucosidase in 20 min is about 25% and 90% respectively.
