The sour orange (Citrus aurantium), bitter orange or is a plant of the rue family (Rutaceae) which looks like the sweet orange, but the flavor of the fruit is very different.
The sour orange fruit has a round with a diameter of about 7.5 cm, but this is slightly flattened at both ends. The aromatic rind is orange or reddish orange and rough. The flesh is bitter.
The fruit of the bitter orange is used for marmalade, beverages (including liquor, such as bitter orange) and confectioneries. From the blossom is an essential oil and a absolue recovered which are used as fragrance or flavor in perfume, and, for example, cola. The essential oil called neroli or neroliolie. The peel of the bitter orange, Curacao Hulls called, are among others used in the brewing of wheat beer and other beers.