单宁酸

例句：

1. 1. The wine is aged in oak barrels to enhance its flavor and complexity.
   这款酒在橡木桶中陈年，以提升其风味和复杂性。
2. 2. The tea contains a unique compound called tannic acid that gives it its characteristic color.
   这种茶含有一种独特的化合物，叫做鞣酸，赋予了它特有的颜色。
3. 3. The tannic acid in the wine helps to protect the grapes from spoilage during fermentation.
   葡萄酒中的鞣酸有助于保护葡萄在发酵过程中不受腐败。