Introduction: Purple-red dishes like purple cabbage and eggplant are rich in anthocyanins, which appear a beautiful red under acidic conditions, but turn blue or black if the conditions are alkaline.
Cut lotus root or potato slices quickly turn brown. This is because the polyphenolic substances in the lotus root or potato undergo oxidation catalyzed by polyphenol oxidase. Adding a little vinegar can inhibit the activity of the oxidase, making it less prone to discoloration.
Purple-red dishes like purple cabbage and eggplant are rich in anthocyanins, which appear a beautiful red under acidic conditions, but turn blue or black if the conditions are alkaline. Therefore, when stir-frying purple-red vegetables like purple cabbage, adding a little vinegar can make the dish's color more vibrant and bright.
When stir-frying green leafy vegetables like油菜 (rapeseed), it's best not to add vinegar. This is because green vegetables contain a large amount of chlorophyll and magnesium, which are bound together. Once vinegar is added, it can cause the green vegetables to lose magnesium, causing them to turn yellow and wilt, which affects their appearance.