A preservative is a natural or synthetic chemical that is added to products such as foods, pharmaceuticals, paints, biological samples, wood, etc. A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. to prevent decomposition by microbial growth or by undesirable chemical changes. Decomposition (or spoilage) refers to the break down of tissue of a formerly living Organism into simpler forms of matter
Preservatives may be added to wood to prevent the growth of fungi as well as to repel insects and termites. Wood is hard fibrous lignified structural tissue produced as secondary Xylem in the stems of Woody plants notably trees but also shrubs A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ Insects ( Class Insecta) are a major group of Arthropods and the most diverse group of Animals on the Earth with over a million described The termites are a group of Social Insects usually classified at the taxonomic rank of order Isoptera (but see also taxonomy Typically arsenic, copper, chromium, borate, and petroleum based chemical compounds are used. Arsenic (ˈɑrsənɪk is a Chemical element that has the symbol As and Atomic number of 33 Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 Chromium (ˈkroʊmiəm is a Chemical element which has the symbol Cr and Atomic number 24 Borates in Chemistry are Chemical compounds containing Boron bonded to three Oxygen atoms written as B(OR3 Petroleum ( L petroleum, from Greek πετρέλαιον, lit A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. For more information on wood preservatives, see timber treatment, lumber, and creosote. All measures that are taken to ensure a long life of wood fall under the definition wood preservation (timber treatment Lumber or timber is Wood in any of its stages from felling through readiness for use as structural Material for Construction, or Creosote is the name used for a variety of products including wood creosote and coal tar creosote.
Preservative food additives can be used alone or in conjunction with other methods of food preservation. Food additives are substances added to food to preserve flavour or improve its taste and appearance Food preservation is the process of treating and handling Food in a way that preserves its edibility and nutrition value Preservatives may be anti-microbial preservatives, which inhibit the growth of bacteria and fungi, or antioxidants such as oxygen absorbers, which inhibit the oxidation of food constituents. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ An antioxidant is a Molecule capable of slowing or preventing the oxidation of other molecules Oxygen supports the growth of microorganisms and causes changes in color and rancid odors in packaged foods Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state Common anti-microbial preservatives include calcium propionate, sodium nitrate, sodium nitrite, sulfites (sulfur dioxide, sodium bisulfite, potassium hydrogen sulfite, etc. Calcium propionate or calcium propanoate has the formula Ca ( C 2 H 5 C[[Oxygen O]] O)2 Sodium nitrate is the Chemical compound with the formula NaNO3 Sodium nitrite, with Chemical formula Na[[Nitrogen N]] O 2 is used as a Color fixative and Preservative in meats and Sulfites (also sulphites) are compounds that contain the sulfite Ion S[[oxygen O]]32− Sodium hydrogen sulfite or sodium bisulfite is a Chemical compound with the Chemical formula NaHSO3 Potassium hydrogen sulfite or potassium bisulfite is a Chemical compound with the Chemical formula KHSO3 ) and disodium EDTA. EDTA is a widely used abbreviation for the Chemical compound ethylenediaminetetraacetic acid (and many other names see table Antioxidants include BHA and BHT. An antioxidant is a Molecule capable of slowing or preventing the oxidation of other molecules Other preservatives include formaldehyde (usually in solution), glutaraldehyde (kills insects), ethanol and methylchloroisothiazolinone. Formaldehyde is a Chemical compound with the formula H2CO It is the simplest Aldehyde —an organic compound containing a terminal Carbonyl Glutaraldehyde is a colorless liquid with a pungent odor used to sterilize medical and dental equipment Methylchloroisothiazolinone (5-chloro-2-methyl-4-isothiazolinon-3-one is a Preservative with antibacterial and antifungal effects within the group of Isothiazolinones 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. Food science is a discipline concerned with all technical aspects of Food, beginning with Harvesting or slaughtering, and ending with its Cooking Toxicology (from the Greek words toxicos and logos) is the study of the adverse effects of Chemicals on living organisms
Natural substances such as salt, sugar, vinegar, and diatomaceous earth are also used as traditional preservatives. Salt is a Dietary mineral composed primarily of Sodium chloride that is essential for Animal life but toxic to most land plants Sugar is a class of edible Crystalline substances mainly Sucrose, Lactose, and Fructose. Vinegar is an acidic liquid processed from the Fermentation of Ethanol in a process that yields its key ingredient Acetic acid (also called ethanoic acid Diatomaceous earth (ˌdaɪətəˈmeɪʃəs ˈɝθ also known as DE, TSS, diatomite, diahydro, kieselguhr, kieselgur and Certain processes such as freezing, pickling, smoking and salting can also be used to preserve food. Frozen food is food preserved by the process of Freezing. Freezing food is a common method of Food preservation which slows both food decay and by Pickling, also known as brining or corning, is the process of preserving Food by Anaerobic fermentation in Brine (a solution Smoking is the process of flavoring, Cooking, or preserving Food by exposing it to the Smoke from burning or smoldering plant materials Salting is the preservation of Food with salt. It is related to Pickling (preparing food with brine rather than dry salt 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. Citric acid is a weak organic Acid. It is a natural Preservative and is also used to add an acidic or sour taste to foods and Soft drinks This article deals with the molecular aspects of ascorbic acid The lemon ( Citrus × limon) is a hybrid in cultivated wild plants Citrus is a common term and Genus of Flowering plants in the family Rutaceae, originating in tropical and subtropical southeast regions of Caution must be taken, however, since FDA standards do not currently require fruit and vegetable product labels to accurately reflect the type of preservative used in the products. Further, there is no current regulation requiring the inclusion of preservative chemical in labels at all; some potentially hazardous.
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.  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.  Allergenic preservatives in food or medicine can cause anaphylactic shock in susceptible individuals, a condition which is often fatal within minutes without emergency treatment. Anaphylaxis is an acute systemic (multi-system and severe Type I Hypersensitivity allergic reaction in humans and other Mammals