Most food will not keep fresh for very long.......fish and Meat will quickly go bad and start to smell.Fruit and vegetable will soon rot. This spoilage is caused by chemical changes in the food....very tiny organisms. These micro-organisms such as yeasts,moulds and bacterie are in the air all around us, and they may grow on all kinds of foods.......cause food to give off smelly gases, to ferment.....some bacteria produce substances.....
......, we must somehow prevent all these things from taking place, or can be used for practically all kinds of foods........, the food is sealed in airtight cans and heated strongly.......by the heat. The ones outside can't get in........