Does anyone know how much sodium has to be in canned soup for preservative purposes?
Various sodium componds including salt can act as a preservative. But as far as I know none of them are needed in canned foods including soup. You can read about how canning preserves food here: http://www.foodsafetysite.com/consumers/resources/canning.html http://www.doityourself.com/stry/howcanningpreserves Basically, bacteria are killed during the preparation of the food, by heating or other processes. Then being deprived of oxygen, any few that do remain can’t multiply, and no more can get in through the airtight container.
