To stop or greatly slow down spoilage of food
Preventing
the growth of bacteria, fungi, and other micro-organisms
the oxidation of fats which cause rancidity
natural aging and discoloration
Drying, freezing, vacuum-packing, canning, pickling, salting, smoking, food irradiation, and adding preservatives, etc.
Various food-spoilage micro-organisms leads development of various modern techn