As apples and pears ripen, the chlorophyll over the skin is replaced by an antioxidant known as nonfluorescing chlorophyll catabolytes (NCCs), according to a latest study conducted by researchers from the University of Innsbruck in Austria and published in the journal "Angewandte Chemie International Edition." Chlorophyll is a chemical which makes plant's leaves green and allowing them to convert sunlight into energy. When a leaf dies, the chlorophyll starts to decay and the leaf loses its green color. This may happen because of injury or age.

Researchers studied the chemicals produced as chlorophyll breaks down and claim to be the first to find the transparent NCCs as one of these products. The decaying of chlorophyll in fruits seems to be linked not to death, but due to ripening. In pears and apples chlorophyll in and just below the peel breaks down into NCCs as the fruit ripens. The researchers discovered that these NCCs are chemically similar to those found in the leaves of apple and pear trees that are in turn similar to each other.

According to the researchers, the presence of NCCs in ripen fruits suggests that they may play a vital nutritional effect in animals which regularly eat fruits, including we humans. NCCs are only the most recent antioxidant that to be identified in fruits and have not yet well-studied. More well-studied are the flavonoids, a large family that includes flavonols, flavones, isoflavones, flavanols and anthocyanidins. Flavonoids are found in high concentrations in citrus fruits, berries, onions, green and black tea, grapes and red wine.