It is best to use the oil for fried dough sticks only once and not to recycle it. During the process of repeated use, especially when the oil is heated at high temperatures and comes into contact with oxygen in the air, it will undergo oxidation and contact with the oxygen in the food. Moisture will cause hydrolysis, eventually causing the oil to turn black, smell and taste unpleasant, and it cannot be used anymore. Similar phenomena occur when oil is stored and cannot be used anymore. At this time, substances harmful to the body have been produced.

Since edible oil is not suitable for long-term storage, you should eat it as you buy it, and store the oil in a dark, low-temperature place. In particular, do not put cooking oil in copper or iron vessels to prevent accelerated oxidation.

Reserve the remaining oil from fried food for the next time you stir-fry or fry. Edible oil is most susceptible to deterioration when heated and cold. When heated to high temperatures repeatedly, edible oil will produce a lot of fatty acid polymers. Fatty acid polymers can stagnate body growth, enlarge the liver, impair liver function, and even cause cancer.