Antioxidants are chemical compounds that provide stability to fats and oils by delaying oxidation reactions.
Antioxidants are chemical compounds that provide stability to fats and oils by delaying oxidation reactions. Antioxidants do not stop oxidation; they merely slow the reaction down.
Generally, antioxidants only involve oil-soluble ingredients but there are some water-soluble antioxidants such as ascorbates.
What causes oxidation?
- The degree of saturation of the fat or oil. Saturated fats such as animal fats tend to be much more stable than unsaturated vegetable oils. The greater the number of unsaturated carbon bonds, the more sites there are for oxidation.
- Catalysts such as metal ions significantly influence oxidation. These may be found in other ingredients, processing equipment or even packaging.
- Oxidation is also influenced by exposure to light, heat, oxygen or enzyme activity.
- While manufacturers can minimise the introduction of metal ions, and remove oxygen with technologies such as gas flushing, rancidity will usually occur in food products containing unsaturated fats, especially once the oxidative resistance of products is broken down.
Oil-soluble antioxidants can be grouped into two categories:
- Natural antioxidants
- Synthetically manufactured antioxidants
Mixed Tocopherols are the most common forms of vitamin E – for use in fats, oils and a wide range of fat-containing food and feed products. Mixes of the natural forms of D-forms of alpha, beta, gamma and delta to Tocopherols are available. HWL usually stocks products such as MTS 70, which contains a minimum of 700 mg/g of mixed Tocopherols.
D alpha Tocopherol is the form of Tocopherol that is retained better in human tissues. It is the only form of Alpha Tocopherol found in nature. The low viscosity and high concentration make D alpha Tocopherol ideal for soft gel capsules.
D alpha Tocopherol acetate
The esters of D alpha Tocopherol have reduced susceptibility to degradation when exposed to air or elevated processing temperatures. These particular benefits allow for flexibility in product formulations. It is D alpha Tocopherol acetate that is being used by ADM in developing water-dispersible and water-soluble products.
D alpha Tocopherol succinate.
These products are available in powder form.
This rosemary extract, from Nutrafur in Spain, is a natural antioxidant, high in carnosic acid, the active component in rosemary. The recommended dose rate depends on the final application but normally ranges between 0.01% to 0.1% of the fat or oil content.
Ascorbic acid is a valuable antioxidant in water-based systems and will preferentially degrade to protect the food system, especially where there is the risk of enzymatic browning. However, in some systems it can degrade to furfural and form brown pigments, so shelf life testing is imperative. Ascorbic acid is readily soluble in water but will degrade quickly to dehydroascorbic acid (DHA), when mixed with oxygen.
Sodium Erythorbate is the sodium salt of iso-ascorbic acid (also known as erythorbic acid) and can be used to slow the rate of enzymatic browning in food products where the acidic impact of ascorbic acid is not appropriate. In meat curing, it controls and accelerates the nitrite curing reaction and maintains the bright red colour in meats. It is used in frankfurters, hams and bacon and is often used in guacamole, beverages and fruit products.
Tartaric Acid is used in food as an antioxidant and synergist to increase the antioxidant effect of other substances. It is also used as an acidity regulator and sequestrant.
Citric acid can also act as a sequestrant for metals and can reduce the rate of oxidation by binding with potential oxidation catalysts.
BHA (Butylated Hydroxyanisole) can be easily applied to food items because of its outstanding solubility in fats and oils and ability to withstand most processing steps. It is renowned for its “carry through” effect into cooked foods, providing extended shelf life.
BHA imparts excellent stability to a vast array of food products, fats, oils, vitamins, pet foods and packaging material.
BHT (Butylated Hydroxytoluene) has a similar functionality to BHA but is generally less heat stable compared to BHA.
It can be used singly or in combination with other antioxidants, and imparts stability to fats, oils, cereals, and packaging material.
Propyl Gallate is noted for its effectiveness in improving the storage life of butter oils, poultry fat, and various other fats and oils.
It is often used in conjunction with BHA and BHT (and citric acid) where it has a synergistic effect. Propyl Gallate may react with metals such as iron or copper and discolour. Propyl Gallate is suggested for use in vegetable oils in countries where regulations currently do not permit the use of TBHQ.
TBHQ (Tertiary Butylhydroquinone) is the most effective choice for highly unsaturated vegetable oils and many edible animal fats.
It has good solubility in oil and provides cost-effective antioxidant protection.
Lecithin, although not classified as an antioxidant, can have an antioxidant effect. Products containing high levels of lecithin tend to be more resistant to oxidation, due to the natural antioxidant capabilities of the phospholipids.
- Vitamin E: Natural antioxidant available in oil and water oil soluble forms, derived from soy
- Rosemary Extract: Oil soluble natural antioxidant
- Ascorbic Acid: Water soluble antioxidant, well suited to fruit systems
- Sodium Erythorbate: Water-soluble antioxidant, also used in meat products.