Canned food, particularly acidic food, can often suffer from problems where
chemical reactions occur between the food and the can. This at best may cause discolouration of the food and at worst may raise the level of
metal oxides in the food to unacceptable levels.
For this reason many cans use an interior coating of
enamel or
lacquer to prevent contact between the food and the metal. Coatings used may include
oleoresins,
phenolics,
vinyl and
epoxy.
It should be noted however that a recent
WWF Toxics Programme Report (http://www.panda.org/toxics/downloads/bisphenol.pdf) raised the spectre of
Bisphenol A or
BPA a known
endocrine disruptor leeching into food from some of these coatings.
I dont know they they are white - aesthetics? or perhaps they are just white