Preservatives (Wikipedia definition)

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 and fungi and mold growth, or antioxidants such as oxygen absorbers, which inhibit the oxidation of food constituents. Common antimicrobial preservatives include calcium propionate, sodium nitrate, sodium nitrite, sulfites (sulfur dioxide, sodium bisulfite, potassium hydrogen sulfite, etc.) and disodium EDTA. Antioxidants include BHA and BHT. Other preservatives include formaldehyde (usually in solution), glutaraldehyde (kills insects), 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 and toxicology, and of course biology.

Natural food preservation
Natural substances such as salt, sugar, vinegar, alcohol, and diatomaceous earth 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 continue to metabolize after they are cut. For instance, citric and ascorbic acids from lemon or other citrus juice can inhibit the action of the enzyme phenolase which turns surfaces of cut apples and potatoes brown.

Health concerns
Some modern synthetic preservatives have become controversial because they have been shown to cause respiratory or other health problems. Some studies point to synthetic preservatives and artificial coloring agents aggravating ADD & ADHD symptoms in those affected. Older studies were inconclusive, quite possibly due to inadequate clinical methods of measuring offending behavior. Parental reports were more accurate indicators of the presence of additives than clinical tests. [3] Several major studies show academic performance increased and disciplinary problems decreased in large non-ADD student populations when artificial ingredients, including preservatives were eliminated from school food programs. [4][5] Allergenic preservatives in food or medicine can cause anaphylactic shock in susceptible individuals, a condition which is often fatal within minutes without emergency treatment.

See Also:
References 1.“Food additives and hyperactive behaviour in 3-year-old and 8-to-9-year-old children in the community: a randomized, double-blinded, placebo-controlled trial”, The Lancet, Sept 2007
2.1997 Graduate Student Research Project conducted at the University of South Florida. Richard W. Pressinger M.Ed.
3."Food Additives May Affect Kids' Hyperactivity", WebMD Medical News, May 24, 2004
4."A different kind of school lunch", PURE FACTS, October 2002
5.The impact of a low food additive and sucrose diet on academic performance in 803 New York City public schools, Schoenthaler SJ, Doraz WE, Wakefield JA, Int J Biosocial Res., 1986, 8(2); 185-195