The Good Side
Sodium metabisulfite is a food additive also known as E223. It is known to be present in fruit juices and candy bars. The primary ingredient of campden tablets for wine and beer making. It also act as whitening agent in some processed fruits.
When used in wine making or any food processing operations. Sodium metabisulfite reacts with acid, forming sulfur dioxide, which act as anti-oxidizing and sanitizing agent. As time progress , the gas is released into the atmosphere or break down and bind with the other components.
The Bad Side
Fine white granular product with a pungent sulfur dioxide gas odor. May irritate the skin. May cause irritations and burns to eyes. Harmful when swallowed or inhaled. May cause severe and fatal allergic reactions if inhaled or swallowed by some asthmatic and other sulfite-sensitive individuals. React with acid to form toxic and irritating sulfur dioxide gas.
Only food grade material is permitted for use as food additive at 0.1% concentration of the total food volume. As of date, many countries prohibit the use of this additive.