domingo, 22 de diciembre de 2019

Antioxidants in Technology

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By Dr. Ananya Mandal, MDReviewed by April Cashin-Garbutt, MA (Editor)

Antioxidants have a variety of uses in the industry. They are most commonly used as food preservatives and supplements. The industrial and other uses of antioxidants can be summarized as follows.

Antioxidants as food preservatives

Antioxidants are used to retard the oxidation of an organic substance. This increases the useful life or shelf life of that material.

For example, in fats and oils, antioxidants delay the onset of oxidation or slow the rate of oxidizing reactions. Fats and oils commonly spoil as oxidation of the lipids cause production of compounds that lead to different odors and taste and continue to affect other molecules in the food. These foods spoil due to exposure to oxygen and sunlight that lead to oxidation of food.

Foods can be preserved by keeping in the dark and sealing it in containers or even coating it in wax, as with cucumbers. However, if the plant products are stored without oxygen that is vital for their respiration, it may lead to unpleasant flavors and unappealing colors. Thus packaging of fresh fruits and vegetables contains around 8% oxygen atmosphere. This may cause oxidant mediated oxidative damage.

The main purpose of using an antioxidant as a food additive is to maintain the quality of that food and to extend its shelf life rather than improving the quality of the food. Antioxidants are an especially important class of preservatives. Unlike bacterial or fungal spoilage of food, oxidative damage can occur even in refrigerated and sealed food items. Antioxidants can prevent this type of food spoilage.

Natural antioxidants and synthetic antioxidants

These preservatives include natural antioxidants such as ascorbic acid (AA, E300) and tocopherols (E306), as well as synthetic antioxidants such as propyl gallate (PG, E310), tertiary butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA, E320) and butylated hydroxytoluene (BHT, E321).

Some of the fats such as olive oil are partially protected from oxidation by their natural content of antioxidants, but remain sensitive to photooxidation or oxidative damage by light.

Antioxidant preservatives are also added to fat-based cosmetics such as lipstick and moisturizers to prevent rancidity. In addition, use of antioxidants also reduces the wastage of raw materials and widens the range of fats that can be used in speciﬁc products.

Antioxidant use in industry

Several industrial products contain antioxidants. Some of these include:

Antioxidants are added to fuels and lubricants to prevent oxidation, and in gasolines to prevent the polymerization - this polymerization of gasoline leads to residues that can damage the engines.
Antioxidants are added to polymers such as rubbers, plastics and adhesives to prevent their oxidative damage and loss of strength and flexibility. Polymers with double bonds are especially vulnerable and benefit with this addition.

The breakdown leads to ozonolysis or cracking. Ozone cracking is especially damaging to elastomers such as natural rubber, polybutadiene and other double-bonded rubbers. They can be protected by antiozonants. Others include polypropylene and polyethylene.

Additives such as AO-22 and 29 are added to turbine oils, transformer oils, hydraulic fluids, waxes, and greases in industrial use. AO-29 is added to gasolines as well.
Additives such as AO-24 are added to low-temperature oils
Additives such as AO-30, 31, 32 and 37 are added to jet fuels and gasolines, including aviation gasolines.

Fuel additive	Components	Applications
AO-22	N	Turbine oils, transformer oils, hydraulic fluids, waxes, and greases
AO-24	N,N'-di-2-butyl-1,4-phenylenediamine	Low-temperature oils
AO-29	2	Turbine oils, transformer oils, hydraulic fluids, waxes, greases, and gasolines
AO-30	2	Jet fuels and gasolines, including aviation gasolines
AO-31	2,4-dimethyl-6-tert-butylphenol	Jet fuels and gasolines, including aviation gasolines
AO-32	2,4-dimethyl-6-tert-butylphenol and 2,6-di-tert-butyl-4-methylphenol	Jet fuels and gasolines, including aviation gasolines
AO-37	2	Jet fuels and gasolines, widely approved for aviation fuels