A preservative is a
substance or a chemical that is added to products such as food products, beverages,
pharmaceutical drugs, paints, biological samples, cosmetics, wood, and many other products to prevent
decomposition by
microbial growth or by undesirable
chemical changes. In general, preservation is implemented in two modes, chemical and physical. Chemical preservation entails adding
chemical compounds to the product. Physical preservation entails processes such as refrigeration or drying.
[Erich Lück and Gert-Wolfhard von Rymon Lipinski "Foods, 3. Food Additives" in ''Ullmann's Encyclopedia of Industrial Chemistry'', 2002, Wiley-VCH, Weinheim. ] Preservative
food 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, freeze-drying, and refrigeration. Chemical preservation and physical preservation techniques are sometimes combined.
Food preservation
Preservatives have been used since prehistoric times.
Smoked meat for example has
phenols and other chemicals that delay spoilage. The preservation of foods has evolved greatly over the centuries and has been instrumental in increasing food security. The use of preservatives other than traditional oils, salts, paints, etc. in food began in the late 19th century, but was not widespread until the 20th century.
The use of food preservatives varies greatly depending on the country. Many developing countries that do not have strong governments to regulate food additives face either harmful levels of preservatives in foods or a complete avoidance of foods that are considered unnatural or foreign. These countries have also proven useful in case studies surrounding chemical preservatives, as they have been only recently introduced. In urban slums of highly populated countries, the knowledge about contents of food tends to be extremely low, despite consumption of these imported foods.
Antimicrobial preservatives
Antimicrobial preservatives prevent degradation by bacteria. This method is the most traditional and ancient type of preserving—ancient methods such as pickling and adding honey prevent microorganism growth by modifying the pH level. The most commonly used antimicrobial preservative is
lactic acid. Common antimicrobial preservatives are presented in the table.
Antioxidants
The oxidation process spoils most food, especially those with a high fat content. Fats quickly turn rancid when exposed to oxygen. Antioxidants prevent or inhibit the oxidation process. The most common antioxidant additives are ascorbic acid ( vitamin C) and ascorbates.[ Thus, antioxidants are commonly added to oils, cheese, and chips.][Msagati, Titus A. M. (2012). The Chemistry of Food Additives and Preservatives. Retrieved from http://www.eblib.com ] Other antioxidants include the phenol derivatives BHA, BHT, TBHQ and propyl gallate. These agents suppress the formation of hydroperoxides.[
]
Nonsynthetic compounds for food preservation
Citric and ascorbic acids target enzyme
An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...
s that degrade fruits and vegetables, e.g., mono/polyphenol oxidase which turns surfaces of cut apples and potatoes brown. Ascorbic acid and tocopherol, which are vitamins, are common preservatives. Smoking entails exposing food to a variety of phenols, which are antioxidants. Natural preservatives include rosemary and oregano extract, hops
Hops are the flowers (also called seed cones or strobiles) of the hop plant ''Humulus lupulus'', a member of the Cannabaceae family of flowering plants. They are used primarily as a bittering, flavouring, and stability agent in beer, to whic ...
, salt, sugar
Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose
Glucose is a sugar with the Chemical formula#Molecular formula, molecul ...
, vinegar, alcohol, diatomaceous earth
Diatomaceous earth ( ), also known as diatomite ( ), celite, or kieselguhr, is a naturally occurring, soft, siliceous rock, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder. It has a particle size ranging fr ...
and castor oil.
Traditional preservatives, such as sodium benzoate have raised health concerns in the past. Benzoate was shown in a study to cause hypersensitivity in some asthma sufferers. This has caused reexamination of natural preservatives which occur in vegetables.
Public awareness of food preservation
Public awareness of food preservatives is uneven. Americans have a perception that food-borne illnesses happen more often in other countries. This may be true, but the occurrence of illnesses, hospitalizations, and deaths are still high. It is estimated by the Centers for Disease Control (CDC) that each year there are 76 million illnesses, 325,000 hospitalizations, and 5,000 deaths linked to food-borne illness.[Theron, M. M. & Lues, J. F. (2007). Organic acids and meat preservation: A review. Food Reviews International, 23, 141-158.]
Food suppliers are facing difficulties with regards to the safety and quality of their products as a result of the rising demand for ready-to-eat fresh food products. Artificial preservatives meet some of these challenges by preserving freshness for longer periods of time, but these preservatives can cause negative side-effects as well.
* Sodium nitrite is a preservative used in lunch meats, hams, sausages, hot dogs, and bacon to prevent botulism and other foodborne pathogens. It serves the important function of controlling the bacteria
Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
that cause botulism, but sodium nitrite can react with protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
s, or during cooking at high heats, to form carcinogenic N- nitrosamines.[Antinoro, L. (2008). EN Rates 12 Common Food Additives As Safe Or Sorry Ingredients. (Cover story). Environmental Nutrition, 31(5), 1-4.]
* The commonly used sodium benzoate has been found to extend the shelf life of bottled tomato paste to 40 weeks without loss of quality.[(Bhat, Rajeev; Alias, Abd Karim; Paliyath, Gopinadham (2011). Progress in Food Preservation. Retrieved from http://www.eblib.com ] However, it can form the carcinogen benzene when combined with vitamin C. Many food manufacturers have reformed their products to eliminate this combination, but a risk still exists.[
]
Preservation of other products
Water-based home and personal care products use broad-spectrum preservatives, such as isothiazolinones and formaldehyde releasers, which may cause sensitization, leading to allergic skin.
See also
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References
External links
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{{Authority control
Chemical substances
Food ingredients