Alkaline surface residue. When adding alkali, the alkaline rice cake is not evenly stirred, which leads to a large amount of alkaline noodles left locally, which will make the alkaline rice cake appear black spots, which is often normal. Alkaline water is a natural alkali, mainly composed of sodium carbonate and potassium carbonate. Its main function is to neutralize gastric acid, which can appropriately relieve the symptoms of belching and acid reflux caused by gastric acid secretion.