There are three types of preservatives: food, organic, and chemical.

1. Food preservatives: benzoic acid and salt: soda, low-salt sauce products, preserved fruits, candies, light soy sauce, vinegar, wine, fruit wine, jam, pulp drinks, barreled concentrate in the food industry Fruit and vegetable juices. Hydrogen peroxide: fresh milk preservation, bag drying.

2. Organic preservatives: benzoic acid and acid salts, sorbic acid and acid salts, esters of parahydroxybenzoic acid, etc. Sorbic acid, benzoic acid, and salts basically exert their bactericidal effect through undissociated molecules.

Both must be converted into corresponding acids to work, so they are called acidic preservatives. Under acidic conditions, it has a certain inhibitory effect on molds, yeasts and bacteria, and is commonly used in the preservative of fruit juices, beverages, cans, light soy sauce, vinegar and other foods. In addition, propionic acid and salt are particularly effective in inhibiting bacteria that produce filamentous slime and have a high safety factor.

3. Chemical preservatives: sulfur dioxide, sulfites and nitrites, etc. Nitrite can inhibit the production of botulinum toxin and avoid botulinum toxin poisoning, but it is mainly used as a color-developing agent. Enzymes that inhibit the activity of certain microbial strains, such as sulfites, have acidic preservative properties, but are mainly used as bleaching solutions. Very rarely added directly to food.