Preservative

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A preservative is a natural or synthetic chemical that is added to products such as foods, pharmaceuticals, paints, biological samples, etc. to retard spoilage, whether from microbial growth or undesirable chemical changes.

Preservatives may be added to wood to prevent the growth of fungi as well as to repel insects and termites. Typically copper, borate, and petroleum based chemical compounds are used. For more information on wood preservatives see timber treatment, lumber and creosote.

[edit] Preservatives in food

Preservative food additives can be used alone or in conjunction with other methods of food preservation. A distinction is sometimes made between anti-microbial preservatives which function by inhibiting the growth of bacteria and fungi, and antioxidants such as oxygen absorbers, which inhibit the oxidation of food constituents. Common anti-microbial preservatives include calcium propionate, sodium nitrate, sodium nitrite, sulphites (sulfur dioxide, sodium bisulfite, potassium hydrogen sulfite, etc.) and disodium EDTA. Antioxidants include BHA and BHT. Other preservatives include formaldehyde (usually in solution), glutaraldehyde, diatomaceous earth (kills insects), ethanol, dimethyl dicarbonate and methylchloroisothiazolinone. The benefits and safety of many artificial food additives (including preservatives) are the subject of debate among academics and regulators specializing in food science and toxicology.

Foods such as salt, sugar or vinegar are also used as preservatives. Another group of preservatives targets enzymes in fruits and vegetables that continue to metabolize after they are cut. For instance, citric and ascorbic acids inhibit the action of the enzyme phenolase which turns surfaces of cut apples and potatoes brown.