Free radicals and food quality

Oxygen is an element indispensable for life. When cells use oxygen to generate energy, free radicals are created as a consequence of ATP (adenosine triphosphate) production by the mitochondria.

A free radical can be defined as an atom or molecule containing one or more unpaired electrons in valency shell or outer orbit and is capable of independent existence.

The presence of an unpaired electron results in certain common properties that are shared by most radicals. Many radicals are unstable and highly reactive. They can either donate an electron to or accept an electron from other molecules, therefore behaving as oxidants or reductants.

If free radicals overwhelm the body’s ability to regulate them, a condition known as oxidative stress ensues. Oxidative stress plays a major part in the development of chronic and degenerative ailments such as cancer, arthritis, aging, autoimmune disorders, cardiovascular and neurodegenerative diseases.

In food, free radicals are derived from major food components or their reactive constituents, such as proteins, lipids, and carbohydrates. The formation and decay of free radicals lead to chemical changes in food and thus affect food quality during processing and storage.

The free radicals promote the development of a series of chemical reactions which lead to the production of off-flavors, colors, odors, and rancidity. While both saturated and unsaturated fatty acids are susceptible to oxidation, unsaturated fatty acids are significantly more susceptible than their saturated counterparts at room temperatures and at elevated temperatures.

Synthetic and natural food antioxidants are used routinely in foods and medicine especially those containing oils and fats to protect the food against oxidation. There are a number of synthetic phenolic antioxidants, butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) being prominent examples.

Tea and rosemary extracts are known as efficient natural antioxidants to prevent lipid oxidation in the food industry. The antioxidant activities of tea and rosemary are associated with the presence of phenolic compounds, which can break the lipid radical chain reaction and thus inhibit lipid oxidation.
Free radicals and food quality

Vitamins as Food Additive

Vitamins as Food Additive
Oxidation, a series of chemical reactions yielding undesirable and products (off odors, colors, and flavors), may occur in many fruits and vegetables and foods high in fat and oil during exposure to air, light, heat, heavy metals, certain pigments or alkaline conditions. Enzymatic browning may occur in some fruits and vegetables, particularly apples, banana, peaches, pear, and potatoes, which contain phenolase enzymes. When these fruits and vegetables are cut or sliced and exposed to air, the phenolases catalyze oxidation of phenolics compounds to ortho-quinone compounds, which then polymerize, forming brown pigments.

Oxidation in lipids (autoxidation) and in fat and oil containing foods, on the other hand, occurs as a result of the susceptibility of fatty acids (building blocks of fats and oils) to oxidations and subsequent formation of reactive compounds referred to as “free radicals”.

The free radicals promote the development of a series of chemical reactions which lead to the production of off-flavors, colors, odors, and rancidity. While both saturated and unsaturated fatty acids are susceptible to oxidation, unsaturated fatty acids are significantly more susceptible than their saturated counterparts at room temperatures and at elevated temperatures.

Antioxidants, as defined by Food and Drug Administration are “substances used to preserve food by retarding deterioration, rancidity or discoloration due to oxidation.” Some oxidations have more than one function. For example, Ascorbic acids may function as a free-radical chain terminator, and oxygen scavenger, or a metal chelator. Under certain conditions, it may act as a promoter for oxidation.
Vitamins as Food Additive