Anthocyanins are naturally occurring compounds that impart color to fruit, vegetables, and plants. Derived from two Greek words meaning plant and blue, anthocyanins are the pigments that make blueberries blue, raspberries red, and are thought to play a major role in the high Antioxidant activity levels observed in red and blue fruits and vegetables. Anthocyanins are also largely responsible for the red coloring of buds and young shoots and the purple and purple-red colors of autumn leaves. Close to 300 anthocyanins have been discovered.
Each fruit and vegetable has its own anthocyanin profile, providing a distinct "fingerprint." Red wine, for example, contains over 15 anthocyanin monomers (type of chemical compound), the varying proportions of which, depending on the type of grape, establish the various shades of the wine's color.
Researchers are attempting to identify the specific bioactivity of each anthocyanin in relation to human health. Variation in pigment results from different degrees of acidity and alkalinity. Intense light and low temperatures favor the development of anthocyanin pigments.
All plant materials contain various pigments, some of which change color as the pH of the plant tissue is changed (for example, by the addition of vinegar or other acids while cooking or processing). An average anthocyanin is red in acid, violet in neutral, and blue in alkaline solution. In fact, when cooking a food that is red, such as red cabbage, it may be helpful to add an acidic substance such as vinegar (or tomato juice or lemon juice) to prevent the food from turning purple.
Many factors influence the stability of anthocyanins. Heat- and light-sensitive, anthocyanin pigments can easily be destroyed during the processing of fruits and vegetables. In particular, in the presence of a high sugar concentration, anthocyanins are rapidly destroyed, thus processed foods containing large amounts of sugar or syrup would not have the same amount of anthocyanins as their unprocessed counterparts.