It is now a common saying that antioxidant is beneficial for health. But what is antioxidant and how does it help us? What are the sources of antioxidants? Before that we should know about oxidation better term autoxidation. In our daily life a continuous process called metabolism is going on in our body, by which we are getting energy from our foods. During this process of metabolism some chemical or elements ( called free radicals -highly reactive atoms or molecular species due to unpaired electrons) are produced in our body which cause some harm full effects on the cells of our body by a process called oxidation. Autoxidation is any oxidation that occurs in open air or in presence of oxygen and/or UV radiation. The process of autoxidation has enormous economic impact, since all foods, plastics, gasoline, oils, rubber, and other materials that must be exposed to air undergo continuous destructive reactions of this type. All good plastics and rubber and most processed foods should contain certain chemical (called antioxidant) to protect them against the attack of oxygen.
The oxidation of food products involves the addition of an oxygen atom to or the removal of a hydrogen atom from the different chemical molecules found in food. Two principal types of oxidation that contribute to food deterioration are autoxidation of unsaturated fatty acids (i.e., those containing one or more double bonds between the carbon atoms of the hydrocarbon chain) and enzyme-catalyzed oxidation.
The autoxidation of unsaturated fatty acids forms free radicals producing compounds that cause the off-flavours and off-odours characteristic of oxidative rancidity. Antioxidants that react with the free radicals (called free radical scavengers) can slow the rate of autoxidation. These antioxidants include the naturally occurring tocopherols (vitamin E derivatives) and the synthetic compounds butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and tertiary butylhydroquinone (TBHQ).
Specific enzymes may also carry out the oxidation of many food molecules. The products of these oxidation reactions may lead to quality changes in the food. For example, enzymes called phenolases catalyze the oxidation of certain molecules (e.g., the amino acid tyrosine) when fruits and vegetables, such as apples, bananas, and potatoes, are cut or bruised become brown in colour. The product of these oxidation reactions, collectively known as enzymatic browning, is a dark pigment called melanin. Antioxidants that inhibit these browning of fruits are reducing substances such as ascorbic acid (vitamin C), and agents that inactivate the enzymes, such as citric acid and sulfites.
In human, free radical injury can be minimised by Antioxidants, which are substances that may protect cells from the damage caused by unstable molecules known as free radicals. Free radical damage may lead to cancer. Antioxidants interact with and stabilize free radicals and may prevent some of the damage free radicals might otherwise cause. Examples of antioxidants include beta-carotene, lycopene, vitamins C, E, and A, and other substances.
Which foods are rich in antioxidants?
Antioxidants are abundant in fruits and vegetables, as well as in other foods including nuts, grains, and some meats, poultry, and fish. The list below describes food sources of common antioxidants.
Beta-carotene is found in many foods that are orange in color, including sweet potatoes, carrots, cantaloupe, squash, apricots, pumpkin, and mangoes. Some green, leafy vegetables, including collard greens, spinach, and kale, are also rich in beta-carotene.
Lutein, best known for its association with healthy eyes, is abundant in green, leafy vegetables such as collard greens, spinach, and kale.
Lycopene is a polymer of beta carotene and a potent antioxidant found in tomatoes, watermelon, guava ( red), papaya, apricots, pink grapefruit, pomegranate, blood oranges, and other foods.( not in strawberry or red berries). Lycopene is heat stable and is available in processed fruits containing natural lycopene e.g tomatoes sauch ( one tomato contain 3.5 mg lycopene but one cup of sauch contain 28 mg lycopene)
Vitamin A is found in three main forms: retinol (Vitamin A1), 3,4-didehydroretinol (Vitamin A2), and 3-hydroxy-retinol (Vitamin A3). Foods rich in vitamin A include liver, sweet potatoes, carrots, milk, egg yolks, and mozzarella cheese.
Vitamin C is also called ascorbic acid, and can be found in high abundance in many fruits and vegetables and is also found in cereals, beef, poultry, and fish.
Vitamin E, also known as alpha-tocopherol, is found in almonds, in many oils including wheat germ, safflower, corn, and soybean oils, and is also found in mangoes, nuts, broccoli, and other foods.
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