It is called preserving the result of the process of handling food in such a way that it prevents or slows down its deterioration (loss of quality, edibility or nutritional values).
This is usually achieved by avoiding the growth of natural grass, yeasts, fungi and other microorganisms, as well as delaying the oxidation of the fats that cause their rancidity. Preserves also include processes that inhibit the natural discoloration that can occur during food preparation, such as the enzymatic browning reaction that occurs after cutting.
Many canning methods include various food preservation techniques. Fruit preserves, for example making jams from them, involve cooking (to reduce humidity and killing bacteria, fungi, etc.), sweetening (to prevent them from growing back) and packing in an airtight jar (to avoid contamination) ). It is important aspects of preserves maintain or improve nutritional values, texture and taste, although historically some methods have drastically altered the character of preserved foods.