Color Phenomena of Black Rice Anthocyanin in Ethanolic Solutions

• Main Authors: Chia-Ming Chang, 張家銘
• Other Authors: 吳瑞碧
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/29625952367936305151

碩士 === 國立臺灣大學 === 食品科技研究所 === 101 === 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.