What are antioxidants and what types exist?
Antioxidants are additives capable of delaying or preventing the rancidity of food due to oxidation, and therefore of lengthening the shelf-life of the products. Other methods that prevent the deterioration of foods can also be considered antioxidants, such as vacuum-sealed or inert gas atmosphere packaging, or freezing, however in this article we will focus mainly on antioxidants that correspond to food additives.
Types of Antioxidants: Natural and Synthetic
There are several types of antioxidants that have been used historically in the food industry, as well as in other industries, such as cosmetics, pharmaceutical or animal nutrition. On the one hand are the natural antioxidants, which are obtained entirely from natural sources, and on the other the synthetic antioxidants, created from chemical processes.
Due to current trends in society to strive for healthier habits and greater expectations for food safety legislation (especially in Europe, North America and some Asian countries), natural antioxidants are experiencing a sustained growth over the last few years. This has been to the detriment of synthetic antioxidants, which, until recently were the most widely used, but lately have been losing ground due to the questions regarding their impact on health.
Below we will list some examples of natural and synthetic antioxidants most used today in the food industry.
Tocopherols (E-306): Tocopherols were one of the first liposoluble antioxidants isolated from plants. Due to their high concentration and habitual presence in vegetable oils, such as soybean or sunflower oil, Tocopherols are presented as the most common antioxidant in nature.
Tocopherols exist naturally as a mixture of four isomers (Alpha, Beta, Gamma and Delta). The antioxidant activity of each isomer is different, as is their vitamin power. Numerous studies show that the antioxidant capacity lies mainly in the gamma and delta isomers, being practically null in the alpha and beta isomers. These antioxidants prevent oxidation of lipids by stopping chain reactions of free radicals.
Tocopherols are a natural antioxidant with a great number of benefits, such as its resistance to high temperatures, its high solubility, its lack of impact on the colour or odour of the final product, or the possibility to be used in organic products. In addition, they are allowed as an antioxidant in any country in the world.
Ascorbic Acid (E-300): Ascorbic Acid is a white crystalline powder used to stabilise beverages, fruits and vegetables. However, its application in fats and oils is limited due to its lipid insolubility.
This additive acts as an antioxidant through the extinction of oxygen, the reduction of free radicals and the regeneration of primary antioxidants. It is considered to be safe as a food additive and has no use limits.
In addition to its antioxidant activity, it acts as vitamin C, a flavouring, acidulant, colour fixative and reducing agent.
Ascorbic acid is very susceptible to elements such as heat, light or oxygen, so it is often necessary to add it exogenously to food.
Rosemary Extract (E-392): This antioxidant is an extract obtained from the Rosemary plant using solvents suitable for human consumption. Its most important compounds from the antioxidant point of view are Rosmarinic Acid, Carnosol and Carnosic Acid.
Rosemary Extract is an antioxidant with good performance in animal fats, but it has some problems related to smell and taste in the doses that guarantee good stability, which is why sometimes it is necessary to undergo a deodorisation and discolouration process, making the product more expensive.
Rosemary Extract is usually combined with other antioxidants such as Tocopherols; together they have a synergistic effect.
BHA (E-320) and BHT (E-321): These compounds are two phenolic antioxidants, capable of stabilising free radicals by isolating them and preventing chain reactions. Both antioxidants are effective in animal fats, however, they are less effective in vegetable fats and oils.
Due to their chemical structures they are extremely volatile, so they are not recommended for methods that involve thermal processes, such as baking or frying. These antioxidants have a slight phenolic odour, so they may be undesirable additives in foods that undergo high temperature processes for an extended time.
BHA is a white, waxy solid sold in the form of flakes or tablets. BHT is white crystalline solid.
In Japan their use is prohibited, in Australia their consumption is prohibited for minors, and in Europe their use is limited. This is because there are indications that they can be harmful to our health.
TBHQ (E-319): TBHQ is an antioxidant commonly used in vegetable oils and animal fats. As an antioxidant, it is more effective in vegetable oils than BHA and BHT. It is heat-stable and is considered an effective antioxidant in the prevention of oxidation of frying oils.
Like other synthetic antioxidants, there are indications that in high doses it can be harmful to health, so in Europe its use in food and has been banned, and in the United States limits have been set for its use.
Propyl Galate (E-310): It is an antioxidant that is widely used in foods where the use of other liposoluble synthetic antioxidants such as BHA, BHT or TBHQ is not appropriate. This antioxidant also works synergistically with other natural and synthetic antioxidants.
Propyl Galate is sensitive to high temperatures, so it does not survive during cooking or frying. However, it is used in different vegetable oils, in the creation of artificial aromas and in some animal feeds.
These are some examples of the most commonly used natural and synthetic antioxidantswithin the food industry.
As a general rule, antioxidants for food use should be economical, safe, effective in low concentrations, capable of surviving processing, stable in finished products and not create any undesirable effects on colour, taste and odour. At present, there is no antioxidant that meets all of these requirements, so the selection of antioxidants will depend on factors such as application, compatibility, regulatory guidelines or market trends.
In this sense, natural antioxidants are those that have been opening new paths in recent years and are being increasingly used by leading companies, such as food and other industries like cosmetics or animal nutrition.