1, lotus root will turn black after heating because it is rich in iron, which will oxidize and darken when heated. Therefore, it is best to use ceramic or stainless steel utensils for cooking, and avoid using iron pots, aluminum pot and iron knives to reduce the problem of oxidation blackening.

It is not difficult to keep the lotus root white. Blanching lotus roots in boiling water at 100℃ for 70 seconds can inactivate all polyphenol oxidase, thus preventing the transformation of polyphenols into quinones.

3. Too long cooking time, repeated heating, and too high temperature (such as using a pressure cooker) will make the oxidation full, and the lotus root will slowly turn black when cooking soup. Therefore, lotus root soup should not be cooked slowly for too long.

4. In addition to high temperature treatment, proper addition of acidic substances can also bind the hands and feet of polyphenol oxidase. For example, adding vinegar can largely avoid the catalytic effect of polyphenol oxidase and keep the lotus root white. Method: Prepare a pot of cold water, put a certain amount of white vinegar in the cold water, and soak the lotus root in it for a while. Acidic substances can inhibit the catalytic effect of polyphenol oxidase, so that lotus root will not turn black and discolor and keep its white color.