(1) The role of food additives

　　The rational use of food additives can prevent food spoilage, maintain or enhance the nutrition of food, and improve or enrich the color, aroma and taste of food.

　　(2) The necessity of using food additives

　　In fact, not using preservatives is more dangerous because spoiled food tends to cause food poisoning illness. In addition, in addition to preventing food spoilage, preservatives can also kill toxin-producing microorganisms such as Aspergillus, which is undoubtedly beneficial to human health.

　　(3) Safe dosage of food additives

　　The amount of food additives that do not have any toxic effects or adverse effects on health, expressed in the mass (mg) ingested per kilogram per day, refer to

　　GB 2760-2011 National Food Safety Standard, Standard for the Use of Food Additives.

　　(4) Do not use toxic additives

　　"Hanging white block" is sodium formaldehyde bisulfite, also called hanging white powder hanging white block, the chemical formula is NaHSO2·CH2O·2H2O. It is prepared by reacting zinc powder with sulfur dioxide to generate low sulfurous acid, etc., and then reacting with formaldehyde, condensing it in a vacuum evaporator, and condensing it into a block. "Hanging white block" is white block or crystalline powder, soluble in water. It is relatively stable at room temperature, can decompose sulfurous acid at high temperature, and has strong reducibility, so it has a bleaching effect. It begins to decompose into harmful substances above 80 °C, and the chemical equation of the reaction is:

　　6NaHSO2 · CH2O · 2H2O + 3H2O = 4NaHSO3 + 2HCOONa + HCOOH + 2H2O + 3CH3OH

　　It is decomposed into formaldehyde at 110 °C, and the reaction equation is:

　　NaHSO2˙CH2O = NaHSO2 + CH2O

　　NaHSO2 + H2O = NaHSO3 + 2 "H"

　　It can cause fever, headache, fatigue, loss of appetite and so on. A one-time edible dose of 10g can be life-threatening. "Hanging white block" is mainly used in the printing and dyeing industry as a dye gathering agent and a reducing agent, and its bleaching and antiseptic effect is more obvious.