pH对黄烷-3-醇和没食子酸自氧化褐变的影响——没食子酸作为一种有前景的褐变抑制剂
The influence of pH on auto-oxidative browning of flavan-3-ols and gallic acid as a promising browning inhibitor.
作者信息
Tan Junfeng, Vincken Jean-Paul, Sanders Mark G, Lin Zhi, de Bruijn Wouter J C
机构信息
Laboratory of Food Chemistry, Wageningen University, P.O. Box 17, 6700, AA, Wageningen, the Netherlands; Tea Research Institute, Chinese Academy of Agricultural Sciences, 9 Meiling South Road, Hangzhou, Zhejiang 310008, People's Republic of China.
Laboratory of Food Chemistry, Wageningen University, P.O. Box 17, 6700, AA, Wageningen, the Netherlands.
出版信息
Food Chem. 2025 May 1;473:143066. doi: 10.1016/j.foodchem.2025.143066. Epub 2025 Jan 27.
The effect of pH and of flavan-3-ols' structural features on undesired auto-oxidative browning of ready-to-drink green tea is still largely unknown. Thus, we investigated auto-oxidative browning of epicatechin (EC), epicatechin gallate (ECg), epigallocatechin (EGC), epigallocatechin gallate (EGCg) in pH-regulated aqueous model systems. In the typical pH range of green tea infusions (pH 5-7), the brown color intensity of flavan-3-ols after auto-oxidation was found to be EC > ECg > EGCg > EGC. Characterization of brown auto-oxidation products by RP-UHPLC-ESI-HRMS revealed that most of these can only be formed through multi-step reactions. Therefore, oxidation potentials of the starting flavan-3-ols are unsuitable for predicting browning. Browning inhibition in real green tea can be achieved by maintaining a pH below 4 with either conventional additives (i.e. ascorbic or citric acid) or with gallic acid, a compound naturally abundant in tea. In conclusion, gallic acid is a promising candidate for clean-label auto-oxidative browning inhibition.
pH值和黄烷-3-醇的结构特征对即饮绿茶不良自氧化褐变的影响仍 largely unknown。因此，我们在pH调节的水性模型系统中研究了表儿茶素（EC）、表儿茶素没食子酸酯（ECg）、表没食子儿茶素（EGC）、表没食子儿茶素没食子酸酯（EGCg）的自氧化褐变。在绿茶浸出液的典型pH范围（pH 5-7）内，发现自氧化后黄烷-3-醇的棕色强度为EC > ECg > EGCg > EGC。通过RP-UHPLC-ESI-HRMS对棕色自氧化产物进行表征表明，其中大多数只能通过多步反应形成。因此，起始黄烷-3-醇的氧化电位不适用于预测褐变。通过使用传统添加剂（即抗坏血酸或柠檬酸）或将pH维持在4以下，或使用茶中天然丰富的化合物没食子酸，可以实现对真正绿茶的褐变抑制。总之，没食子酸是一种有前景的用于清洁标签自氧化褐变抑制的候选物。
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