By Harold McGee
Anthocyanins (from the Greek for “blue flower”) are responsible for most of the red, purple, and blue colors in plants, including many berries, apples, cabbage, radishes, and potatoes. A related group, the anthoxanthins (“yellow flower”) are pale yellow compounds found in potatoes, onions, and cauliflower. This third major class of plant pigments is a subgroup of the huge phenolic family, which is based on rings of 6 carbon atoms with two-thirds of a water molecule (OH) attached to some of them, which makes phenolics soluble in water. The anthocyanins have 3 rings. There are about 300 known anthocyanins, and a given fruit or vegetable will usually contain a mixture of a dozen or more. Like many other phenolic compounds, they are valuable antioxidants.