The Following article is from the annals of the FSTA: Food Science and Technology Abstracts

Antioxidants in foods

It is ironic that the cellular activities which keep our bodies alive actually generate reactive oxygen molecules (free radicals) as highly destructive by-products. These free radicals, which are also produced following exposure to a number of external hazards (including UV light, X-rays and environmental pollutants), can cause extensive damage to the nucleic acid, protein, lipid and carbohydrate components of our cells and are therefore believed to contribute to some of the degenerative diseases of ageing, such as cardiovascular disease, cancer, cataracts, immune system decline and brain dysfunction.

Many of us are familiar with the hypothesis that foods rich in antioxidants may afford a degree of protection against free radical damage and make a concerted effort to eat a well-balanced diet which includes a range of antioxidant-rich foods and beverages (see Table 1) such as fruit and vegetables, cereals and nuts, tea, and, last but not least, the occasional glass of red wine!

Antioxidants are not only important to the health conscious consumer; food manufacturers also rely on these chemicals to maintain the shelf life of foods. Just as the molecular components of our cells are susceptible to free radical damage, so too are many of the components which make up the foods we eat, with fats and oils especially prone to oxidative damage.

Signs of oxidation in foods (which occurs by 2 basic processes – autoxidation and photo-oxidation) include: rancidity (the oxidation of fats and oils and the production of off flavours and odours); colour changes (fats and oils generally darken in colour whilst pigments lighten in response to oxidation); flavour loss; and less obviously, changes in the nutritional value of products (the destruction of essential fatty acids and lipid soluble vitamins (A, D, E and K) and a decrease in caloric content).

Synthetic antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG) and tert-butyl hydroquinone (TBHQ) have, for many years, been incorporated into foods to control oxidation and retain food quality. These antioxidants are most effective when added to foods as early as possible during processing and are generally incorporated into fats and oils at the raw materials stage. Alternatively, antioxidants can be dissolved in food-grade solvents and sprayed onto foods or incorporated into packaging materials and allowed to volatilize into the enclosed product.

Once incorporated into a given food matrix, antioxidants employ a range of mechanisms to suppress oxidative damage, such as free radical scavenging or inactivation, pro-oxidant metal ion chelation or the quenching of secondary products of oxidation. Through these mechanisms, synthetic antioxidants have been both effective and economical for inhibiting oxidative changes and prolonging the shelf life of foods.

However, consumers are increasingly demanding "additive free" and "natural" diets. The commercial development of natural antioxidant sources both for nutritional purposes and for their preservative effects is therefore of major interest to the global food industry.

The best known sources of natural antioxidants for preventing food spoilage include vitamin C, carotenoids, tocopherols and extracts from herbs, spices and tea. Plants such as rosemary, thyme, marjoram, clove and ginger attribute their antioxidant activity to naturally occurring phenolic compounds. Rosemary extract is the most widely used spice antioxidant and is commonly added to meats and meat products, dressings, and fats and oils to inhibit oxidative degradation of these foods.

Vitamin E is also an effective natural antioxidant. By supplementing the feeds of poultry, swine and cattle with this vitamin it is possible for animals to incorporate the antioxidant compound directly into their muscle tissues resulting in meats with much improved lipid stability compared with meats from animals fed standard diets.