In canned fishery products (and with other proteinaceous packs such as meat and corn), it is customary to use sulphur resistant (SR) lacquer systems to prevent the formation and iron sulphides on the plate. Due to the inclusion of white zinc oxide, SR lacquers have a milky appearance. The reason for the inclusion of the zinc is that it reacts with the sulphur compounds released from the proteins during thermal processing, to form zinc sulphide precipitates readily be detected against the background of the opaque acquer.. Another lacquer system finding use for meat and fish packs relies on the physical barrier provided by the inclusion of aluminium pigments in an epoxy phenolic (epon) lacquer. These lacquers, often referred to as V-enamels, are common in pet food cans.