145. Discoloration and Corrosion in Canned Cream

Abstract

Several defects in canned cream after some months' storage have been classified: (1) “purpling” of the can, due to a film of tin sulphide, (2) pitting of the can, associated with (3) formation of black patches and of black specks in the body of the cream, consisting of ferrous sulphide, stannous oxide or both. “Purpling” is produced by excessive time and temperature of sterilization, owing to the liberation of active sulphur compounds which attack the tin. Addition of sodium bicarbonate up to 5 g. per gallon has, if anything, a slightly beneficial effect.