When finishing yam, whether peeling or cutting, you must not use a metal knife, but use a wood, bamboo or plastic knife to solve it.

After cutting the yam, soak it in clear water and drain it when frying. The same is true of lotus root slices, which will turn black when exposed to air. Wild yam is more suitable for soup, and artificially planted yam is suitable for cooking. Cutting yam with metal knife will produce oxidation and make yam black, so it is best to use bamboo knife or plastic knife when cutting yam. You can also soak the cut yam in cold water with vinegar or lemonade, and then take out the decanter when cooking, so that the yam will not turn black even if it is not eaten immediately.