08-11-2017, 09:07 AM
A preservative is a substance or chemical that is added to products such as food, beverages, drugs, paints, biological samples, cosmetics, wood and many other products to prevent decomposition due to microbial growth or undesirable chemical changes. In general, preservation is implemented in two modes, chemical and physical. Chemical conservation involves adding chemical compounds to the product. Physical preservation involves processes such as cooling or drying. Food preservative additives reduce the risk of foodborne infections, decrease microbial spoilage and preserve fresh attributes and nutritional quality. Some physical techniques for food preservation include dehydration, UV-C radiation, lyophilization and refrigeration. Chemical preservation and physical preservation techniques are sometimes combined.
Food preservation is to prevent the growth of microorganisms (such as yeast) or other microorganisms (although some methods work by introducing benign bacteria or fungi into food), as well as slowing the oxidation of the fats that cause rancidity. Food preservation may also include processes that inhibit visual deterioration, such as the enzymatic browning reaction in apples after they are cut during food preparation.
Many processes designed to preserve food involve more than one method of food preservation. Preserving the fruit by turning it into marmalade, for example, involves boiling (to reduce the moisture content of the fruit and killing bacteria, etc.), sweetening (to prevent them from growing back) and sealing inside an airtight jar (to avoid recontamination). It has been shown that some traditional methods of food preservation have a lower energy input and carbon footprint, compared to modern methods.