One of the simplest food preservation methods is to changed the atmosphere around the food. This is termed modified atmosphere packing (MAP). The proportion of the gases normally present around a product is modified to contain, for example, lower levels of oxygen and higher levels of nitrogen and carbon dioxide. This slows down the growth of many spoilage organisms and extends shelf life. MAP should also be combined with correct chilled temperature control in order to guarantee the control of microbial proliferation.
The restriction of oxygen
The development of oxidation rancidity and the growth of strict aerobes such as moulds can be prevented by vacuum packing, although sufficient oxygen normally remains in vacuum packs of meat to facilitate the growth of some aerobes. Complete removal of oxygen allows the growth of anaerobes such as Clostridium perfringens. Vacuum packs of cooked meat must be stored under refrigeration to achieve a reasonable shelf life.