SULPHUR STAINING IN CANNED FOODS: its diagnosis and prevention

ALTHOUGH the staining of tinplate cans by foods rich in protein or containing organic sulphur compounds has been recognised for a very long time as a natural phenomenon, it nevertheless continues to give rise to occasional complaints. The chemistry of the reactions involved is not well understood, but it is supposed from observation of the formation of the stains that decomposition of sulphur compounds takes place during processing of the cans with the formation of simpler water‐soluble or gaseous substances that subsequently react with the tin surface to form a film of sulphide. It has been reported that the reaction continues during storage and that, in consequence, staining increases during storage.