What is sodium metabisulfite of food additive?

Sodium pyrosulfite is a white or yellowish crystalline powder with a strong SO2 odor. Sodium pyrosulfite is more strongly reducing than sulfite and acts in a similar way to sodium sulfite.
The use of sodium metabisulfite in processed foods should pay attention to the following points: 1) sodium metabisulfite real reducing bleach, its solution is unstable and volatile, so it should be used now to prevent sulfite instability and volatilization.
2) When metal ions exist in food, the residual sulfite can be oxidized; It can also make the reduced pigment oxidize and discolor, thereby reducing the effectiveness of the bleach agent. So metal chelating agents are used in the production process.
3) Substances bleached with sulfites are easy to recolor due to the disappearance of sulfur dioxide, so excessive sulfur dioxide is usually left in food, but the residual amount must not exceed the standard.
4) sulfite can not inhibit the activity of pectinase, will damage the cohesion of pectin. In addition, after sulfite penetrates into the fruit tissue, the fruit is broken during processing in order to remove the sulfur dioxide, so the fruit stored with sulfite is only suitable for making jam, dried fruit, fruit wine, preserves, etc., can not be used as raw materials for cans.
5) Sulfites can destroy thiamine, so it is not easy to use in fish food.

6) Sulfites are easy to react with aldehydes, ketones, proteins, etc.
Storage precautions: Store in a cool, dry and well-ventilated warehouse. Keep away from fire and heat. Keep the container sealed. It should be stored separately from oxidants, acids and edible chemicals, and should not be mixed. Should not be long, so as not to deteriorate. Storage areas should be equipped with suitable materials to contain leaks.
Storage and validity: dark, sealed storage.
The application of sodium metabisulfite in food: At present, it is in the processing and preservation process of light-colored vegetables in China, such as mushrooms, lotus root, horseshoe, white asparagus, yam and other products. More use of sodium metabisulfite solution for color protection, of course, there are some differences in the process of each factory, such as in the processing of canned mushrooms, the fresh mushrooms are soaked in an aqueous solution containing sodium metabisulfite 0.03g/kg in time for 2 times, each time for 1-2min.

Sodium metabisulfite is used in the cookie industry as a cookie dough improder, which is prepared into a 20% solution before use and added to the immature dough in batches during the dough preparation process.
Due to the reduction of the sulfur dioxide released by sodium metabisulfite in the process of dough preparation, when the strength and toughness of flour gluten are large, a small amount of addition can prevent the deformation of the finished cookie due to excessive strength. Toughness dough can be added according to the strength of the flour, and generally not used in the crisp dough with a high proportion of oil and sugar, because the addition of oil and sugar itself has prevented the water absorption and expansion of gluten protein, preventing the formation of a large number of gluten, without adding sodium metabisulfite.