oxygen availability. by removing air form around food, or using vacuum packaging, or modified atmosphere packaging, the food's shelf life may be extended. however, some microorganisms con grow in environments without oxygen so production processes need to control these microorganisms as well. i light standards of hygiene are still important as these packaging methods only limit the growth of spoilage organisms that need oxygen they do not kill them or limit the growth of organisms that grow in the absence of oxygen; for example the bacteria that cause slime,botulism or listeriosis.