1. Lotus root will turn black after being heated because it is rich in reducing substances such as vitamin C and iron, which will oxidize when exposed to heat and become darker in color. When stewing lotus roots, it is best to use ceramic or stainless steel utensils. Avoid using iron or aluminum pots, and try not to use iron knives to cut lotus roots to reduce oxidation.

2. When frying lotus roots, it is best to cut them into the pot immediately. Do not leave them in the air for a long time because they will oxidize. If you can't cut and fry them now, you can cut them and put them in water, then pick them up while frying. The fried lotus roots will be white, crisp and tender.