Department of Food Science and Biotechnology, National Chung Hsing University, 145 Xingda Rd., South Dist., Taichung City 40227, Taiwan.
Molecules. 2018 Jun 5;23(6):1357. doi: 10.3390/molecules23061357.
Roselle is rich in anthocyanins and is traditionally used to prepare a bright red beverage by decoction. However, heat treatment and different pH environments are often encountered during food processing, and these factors are often detrimental to anthocyanins. Therefore, it is very important to understand the influence of pH and heat treatment on anthocyanins for the application of roselle. This study determined the antioxidant properties of roselle extract, explored changes in the color and anthocyanin content in different pH environments, and evaluated the thermal stability of roselle anthocyanins using kinetic equations. The results showed that the roselle extract is rich in anthocyanins and has good antioxidant capacity (DPPH IC50 = 4.06 mg/mL, ABTS IC50 = 3.7 mg/mL). The anthocyanins themselves exhibited a certain degree of heat resistance and good color stability in an acidic environment. In contrast, they degraded very quickly and exhibited significant changes in color in a low-acid environment. The activation energy (a) ranges of the anthocyanins in the acidic and low-acid environments were quite different at 55.8⁻95.7 and 31.4⁻74.9 kJ/mol, respectively. Thus, it can be concluded that roselle anthocyanins are susceptible to heat treatment in a low-acid environment, affecting their quality and appearance; however, they can serve as a good source of functional ingredients and color in an acidic environment.
洛神花富含花青素，传统上通过煎煮来制备鲜艳的红色饮料。然而，在食品加工过程中经常会遇到热处理和不同的 pH 值环境，这些因素通常对花青素不利。因此，了解 pH 值和热处理对洛神花中花青素的影响对于洛神花的应用非常重要。本研究确定了洛神花提取物的抗氧化特性，探讨了不同 pH 值环境下颜色和花青素含量的变化，并使用动力学方程评估了洛神花花青素的热稳定性。结果表明，洛神花提取物富含花青素，具有良好的抗氧化能力（DPPH IC50 = 4.06 mg/mL，ABTS IC50 = 3.7 mg/mL）。花青素本身在酸性环境中具有一定的耐热性和良好的颜色稳定性。相比之下，它们在低酸度环境中降解非常迅速，颜色发生明显变化。花青素在酸性和低酸性环境中的活化能（a）范围分别为 55.8⁻95.7 和 31.4⁻74.9 kJ/mol，差异很大。因此，可以得出结论，洛神花花青素在低酸度环境中易受热处理影响，从而影响其质量和外观；然而，它们可以在酸性环境中作为功能性成分和颜色的良好来源。
