Chew Ying Ming, Hung Chien-Hsiu, King V An-Erl
Department of Food Science and Biotechnology, National Chung Hsing University, 145 Xingda Road, South District, Taichung City, 402 Taiwan, ROC.
J Food Sci Technol. 2019 Mar;56(3):1595-1600. doi: 10.1007/s13197-019-03673-1. Epub 2019 Mar 4.
Betalains are nitrogen-containing colorants with antioxidant properties that can be found in plant materials such as pitaya peels. However, thermo-stability of these natural colors may vary with different source, yet few study has reported the rate orders of degradation for pitaya-sourced betalains. In this study, accelerated storage test of betalains, namely betacyanin and betaxanthin, extracted from pitaya peel are investigated by heat treatment of the extract at elevated temperatures. The results show that degradation kinetics of betacyanins and betaxanthins can both fit first-order kinetics and Arrhenius equation with activation energies at - 49.2 kJ/mol and - 40.0 kJ/mol, respectively. The result of Student's t-test indicated that the predicted k values are statistically the same as compared to their corresponding experimental values. LSD estimation also showed that k value variation tendency of the two betalains appears to be the same at 60 °C or below, while betacyanins tend to degrade faster above 80 °C than betaxanthins due to higher coefficient value of k value variation. This result also suggests that the pitaya-sourced betalains tend to degrade gradually even though they are stored under refrigerated condition. However, the betalains showed appreciably lower rate of degradation if they are processed at 60 °C or below.
甜菜色素是一类具有抗氧化特性的含氮色素，可在火龙果果皮等植物材料中找到。然而，这些天然色素的热稳定性可能因来源不同而有所差异，不过鲜有研究报道火龙果来源的甜菜色素的降解速率阶数。本研究通过在高温下对从火龙果果皮中提取的甜菜色素（即花青素和黄嘌呤）提取物进行热处理，研究了其加速储存试验。结果表明，花青素和黄嘌呤的降解动力学均符合一级动力学和阿伦尼乌斯方程，活化能分别为 -49.2 kJ/mol 和 -40.0 kJ/mol。学生 t 检验结果表明，预测的 k 值与相应的实验值在统计学上相同。最小显著差数法估计还表明，两种甜菜色素在 60°C 及以下时 k 值变化趋势似乎相同，而在 80°C 以上时，由于 k 值变化系数较高，花青素比黄嘌呤降解得更快。这一结果还表明，即使火龙果来源的甜菜色素储存在冷藏条件下，它们也会逐渐降解。然而，如果在 60°C 及以下进行处理，甜菜色素的降解速率会明显降低。
