Atmospheric (Triplet) oxygen is a low energy biradical (i.e., contains two unpaired electrons). However, during metabolism of oxygen as well nitrogen, alterations can occur to produce highly reactive oxygen and nitrogen species that will react with and cause damage to biomolecules. In foods, this can cause oxidation of lipids, pigments, vitamins, and proteins, leading to offflavor formation, discoloration, and loss of important nutrients. Foods, which are derived from a variety of different biological tissues, contain a host of different antioxidant defense systems to prevent the damaging effect of reactive oxygen and nitrogen species. However, during the processing of biological tissues into foods, the formation of oxidizing species can increase and antioxidant systems can be overwhelmed leading to uncontrolled oxidative reactions resulting in loss of quality, decrease in shelflife, and formation of potentially toxic oxidation products. To protect food quality and safety, antioxidants are often added to processed foods. These antioxidants can be synthetically derived compounds, such as butylated hydroxytoluene and ethylene diaminetetraacetic acid. Concern over the use of synthetic food additives has driven the food industry to find effective natural antioxidants additives that are derived from biological sources. In addition, efforts to decrease oxidative deterioration have focused on the development of food processing techniques that preserve endogenous antioxidants and nutritional schemes that increase natural antioxidants in animal-derived foods.
In addition to the association of natural antioxidants with food quality, these compounds have also been associated with health benefits. The association of the protective effects of fruits and vegetables in the diet against diseases, such as cancer and cardiovascular disease, has been established for years. Comprehensive reviews on the consumption of fruits and vegetables with cancer rates have shown that 60–85% of the studies have a statistically significant association with the decrease of cancer incidence. Individuals who consume the highest amount of fruits and vegetables have half the cancer rate as those who consume the least amount. A similar association has been seen with cardiovascular disease, with 60% of the studies reviewed showing statistically significant protective effects. The consumption of an ample supply of fruits and vegetables provides a wide variety of phytochemicals that have been shown to have health benefits and antioxidant activity. The natural antioxidants with health benefits include ascorbic acid, α-tocopherol, β-carotene, and plant phenolics.
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