西印度櫻桃果皮色素穩定性及抗氧化力之探討

Pigment Stability and Antioxidant Capacity of the Pericarp of West Indian Cherries (Malpighia punicifolia L.)

西印度櫻桃富含維生素C，然色素不穩定，易生褐變，致其加工品之發展為之受限。為了解其色素之基本特性，進而加以利用，本研究以省產西印度櫻桃為原料，將其果皮色素純化，接著觀察該色素之特性及對pH值與加熱之穩定性，最後則分別以硫氰酸鐵法、DPPH（α，α-diphenyl-β-picrylhydrazyl）清除能力及FRAP（ferric reducing ability of plasma）法，就其果皮之抗氧化能力加以探討。結果顯示，省產西印度櫻桃果皮色素具有花青素malvidin之特性，在520nm有最大吸收波長，並與巨峰葡萄花青素的Rf值最為相近。穩定性方面，該色素於pH 1時最為穩定，隨著pH值增加，A520下降。當加熱至50℃以上時，其花青素即迅速裂解，DI值急速上升。抗氧化力方面，西印度櫻桃果皮中的花青素與抗氧化能力密切相關，當花青素濃度愈高時，其抑制氧化的效果愈佳。當濃度達8 mg／g後，其抗氧化性與α-生育醇及BHA甲醇萃取液之效果相近。至於總酚類與FRAP還原能力，則隨著pH值及加熱溫度之增加而下降，但DPPH清除能力卻反而上升。 Being abundant with vitamin C, the West Indian cherry was quite limited in food processing owing to unstability and rapid browning of its pigment. The purpose of this study was to investigate the pigment extracted and purified from the fruit and its stability under different pH and at different temperatures. Furthermore, the antioxidant capacity examined by the thiocyanide method, the DPPH scavenging ability and FRAP of the pericarp was also investigated. Results showed that the pigment possessed the characteristic of malvidin, with the maximum absorbance at 520 nm and similar Rf of anthocyanin in concord grapes. As to stability, the pigment was found to be quite stable at pH 1. Absorbance at 520 nm decreased as pH increased. Anthocyanin degradation index (DI) increased rapidly after heating, especially when the temperature was over 50 . The antioxidant capac ℃ ity was found to be closely related to the amount of anthocyanin in the pericarp. The sample with the concentration of 8 mg/g pericarp powder showed similar antioxidant capacity to that of α-tocopherol and BHA. When pH increased or the temperature raised, total phenolics and reducing power (FRAP) decreased while the DPPH scavenging ability increased.