The common non-edible substances in catering are poppy shell, industrial gelatin, Sudan red, melamine and clenbuterol.

1. poppy shell: the dried and mature shell of the plant poppy. In autumn, the ripe fruit after cutting the pulp juice is picked, broken, seeds and branches removed and dried. Long-term consumption of food containing poppy shells is easy to addiction, which will also cause damage to the human nervous system and may cause chronic poisoning.

2. industrial gelatin: industrial gelatin is a kind of protein partially hydrolyzed from collagen in connective or epidermal tissues of animals. It has many excellent physical and chemical properties, such as reversible gel formation, adhesiveness and surface activity, and is widely used as jelly, emulsifier, stabilizer, adhesive and clarifier in food industry.

3. Sudan red: lipophilic azo dye, which is mainly used for dyeing products such as oil paint, engine oil, wax and shoe polish. Because the food dyed with Sudan red is very bright and not easy to fade, which can arouse people's strong appetite, some illegal food enterprises add Sudan red to food. Common foods with Sudan red are Chili powder, Chili oil, red tofu, red-hearted eggs and so on.

4. Melamine: commonly known as melamine and albumin, is a triazine nitrogen-containing heterocyclic organic compound, which is used as a chemical raw material. It is a white monoclinic crystal, almost tasteless, slightly soluble in water (3.1g/L at room temperature), soluble in methanol, formaldehyde, acetic acid, hot ethylene glycol, glycerol, pyridine, etc., insoluble in acetone and ethers, and cannot be used in food processing or food additives.

5. Clenbuterol refers to clenbuterol. When it is used in livestock feeding at a dosage 5-11 times higher than the therapeutic dose, it has a significant nutritional "redistribution effect"-it can promote protein deposition in animals, promote fat decomposition and inhibit fat deposition, and can significantly improve carcass lean meat rate, weight gain and feed conversion rate. Therefore, it has been used as a growth promoter and feed additive for cattle, sheep, poultry, pigs and other livestock and poultry.