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A preservative is a naturally occurring or synthetically produced substance that is added to products such as foods, pharmaceuticals, paints, biological samples, wood, etc. to prevent decomposition by microbial growth or by undesirable chemical changes. There are two types of preservatives. Class I preservatives and other one is Class II preservatives.
Class I preservatives
Class I preservatives would be something you would expect to find in a person's kitchen, including vinegar, salt, sugar, honey, vegetable oil. Wood smoke is also considered a Class I preservative.
Class II preservatives
Class II preservatives refers to those preservatives which are chemically manufactured, such as those derived from Benzoic acid and sodium diacetate. Anything derived from potassium or the calcium salts of lactic acid is also a Class II preservative.
Preservatives in wood
Preservatives may be added to wood to prevent the growth of fungi as well as to repel insects and termites. Typically arsenic, copper, chromium, borate, and petroleum based chemical compounds are used. For more information on wood preservatives, see timber treatment.
Preservatives in foods
Preservative food additives can be used alone or in conjunction with other methods of food preservation. Preservatives may be antimicrobial preservatives, which inhibit the growth of bacteria or fungi, including mold or they can be antioxidants such as oxygen absorbers, which inhibit the oxidation of food constituents. Common antimicrobial preservatives include sorbic acid and its salts, benzoic acid and its salts, calcium propionate, sodium nitrite (and sodium nitrate which converts to sodium nitrite "in situ"), sulfites (sulfur dioxide, sodium bisulfite, potassium hydrogen sulfite, etc.) and disodium EDTA. Antioxidants include BHA, BHT, TBHQ and propyl gallate. Other preservatives include ethanol and methylchloroisothiazolinone. FDA standards do not currently require fruit and vegetable product labels to reflect the type of chemical preservative(s) used on the produce. The benefits and safety of many artificial food additives (including preservatives) are the subject of debate among academics and regulators specializing in food science, toxicology, and biology.
Natural food preservation
Naturally occurring substances such as rosemary extract, hops, salt, sugar, vinegar, alcohol, diatomaceous earth and castor oil are also used as traditional preservatives. Certain processes such as freezing, pickling, smoking and salting can also be used to preserve food. Another group of preservatives targets enzymes in fruits and vegetables that start to metabolize after they are cut. For instance, the naturally occurring citric and ascorbic acids in lemon or other citrus juice can inhibit the action of the enzyme phenolase which turns surfaces of cut apples and potatoes brown if a small amount of the juice is applied to the freshly cut produce. Vitamin C and Vitamin E are also sometimes used as preservatives.
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Some modern synthetic preservatives have been shown to cause respiratory or other health problems. For example sulfites are commonly used in wines and some dried fruits or vegetables and are known as possible irritants to people with asthma. In one study, children exhibited increased hyperactivity after consuming drinks containing sodium benzoate or artificial food color and additives. [misleading] Prior studies were however inconclusive.
- Dalton, Louisa (11 2002). "Food Preservatives". Chemical and Engineering News 80 (45): 40. Retrieved 9 February 2012.
- "Using Preservatives". Retrieved 9 February 2012.
- McCann, D.; Barrett, A.; Cooper, A.; Crumpler, D.; Dalen, L.; Grimshaw, K.; Kitchin, E.; Lok, K. et al. (2007). "Food additives and hyperactive behaviour in 3-year-old and 8/9-year-old children in the community: A randomised, double-blinded, placebo-controlled trial". The Lancet 370 (9598): 1560–7. doi:10.1016/S0140-6736(07)61306-3. PMID 17825405.