Sodium metabisulfite is a reducing bleaching agent with an unstable and highly volatile solution. It should be prepared when using to prevent unstable sulfite from volatilizing.

When metal ions are present in food, residual sulfite can be oxidized. It can also oxidize and discolor the reduced pigment, thereby reducing the effectiveness of bleaching. So metal chelating agents should be also used during production.

Substances bleached with sulfites are prone to discolor due to the disappearance of sulfur dioxide, so excess sulfur dioxide is usually left in food, but the residual amount should not exceed the standard.

Sulfite can’t inhibit the activity of pectinase and can damage the cohesion of pectin. In addition, after sulfite infiltrate into the fruit tissue, the fruit should be broken during processing to completely remove sulfur dioxide. Therefore, fruits stored with sulfite are only suitable for making jam, dried fruits, fruit wine, preserves, etc., and cannot be used as raw materials for canned goods.

Sulfite can destroy thiamine, so it is not suitable for fish food.

Sulfite easily reacts with aldehydes, ketones, proteins, etc..

precautions for using sodium metabisulfite