The blood orange is a variety of orange (Citrus sinensis) with crimson, blood-colored flesh. The fruit is smaller than an average orange; its skin is usually pitted, but can be smooth. The distinctive dark flesh color is due to the presence of anthocyanin, a pigment common to many flowers and fruit, but uncommon in citrus fruits. Sometimes there is dark coloring on the exterior of the rind as well, depending on the variety of blood orange. The degree of coloration depends on light, temperature and variety.

The blood orange is often described as a hybrid between the pomelo and the tangerine, but it is actually just a mutation of a sweet orange.

Cultivars

The three most common types of blood oranges are: the Tarocco (native to Italy), the Sanguinello (native to Spain), and the Moro, the newest variety of the three. The other less common types include Khanpur, Washington Sanguine, Ruby Blood, Sanguina Doble Fina, Delfino, Red Valencia, Burris blood Valencia orange, Vaccaro blood orange, Sanguine grosse ronde, Entre Fina blood orange and Sanguinello a pignu. Vainiglia Sanguigno and Cara Cara can be considered in the same category when these are all grouped together as pigmented oranges. Cara Cara or Pink Navel and the Vainiglia Sanguigno's pigmentations are based on lycopene instead of anthocyanins of the true blood oranges.

Moro

The Moro, a recent addition to the blood orange family, is the most colorful of the three types, with a deep purple flesh and reddish orange rind. The flavor is stronger and the aroma is more intense than a normal orange. This fruit has a distinct, sweet flavour with a hint of raspberry particular to blood oranges. The Moro variety is believed to have originated at the beginning of the 19th century in the citrus-growing area around Lentini (in the Province of Siracusa in Sicily) as a bud mutation of the "Sanguigno". Moro are "full-blood" oranges, meaning that the flesh ranges from orange-veined with ruby coloration, to vermilion, to vivid crimson, and nearly to black. The thick orange-colored peel has a medium fine grain with spots or red wine veins.

Tarocco

The Tarocco is a medium-sized fruit and is perhaps the sweetest and most flavorful of the three types. The most popular table orange in Italy, the Tarocco is thought to have derived from a mutation of the "Sanguinello". It is referred to as "half-blood", because the flesh is not accentuated in red pigmentation as much as with the Moro and Sanguinello varieties. It has thin orange skin, slightly blushed in red tones. The Tarocco is one of the world's most popular oranges because of its sweetness (Brix to acid ratio is generally above 12.0) and juiciness. It has the highest Vitamin C content of any orange variety grown in the world, mainly on account of the fertile soil surrounding Mount Etna, and it is easy to peel. The Tarocco orange is seedless, and it contains anthocyanins, as do other blood oranges. The name Tarocco is thought to be derived from an exclamation of wonder expressed by the farmer who was shown this fruit by its discoverer. The University of California Riverside Citrus Variety Collection has delineated three subcultivars of Tarocco: The Bream Tarocco which was originally donated by Robert Bream of Lindsay, California, is of medium to large fruit with few to no seeds; Tarocco #7 or CRC 3596 Tarocco which is one of the most delicious blood orange varieties in the entire Citrus Variety Collection but the rind of this blood orange has very little to no coloration at all, vigorous tree but only moderately productive; and the Thermal Tarocco which was donated by A. Newcomb of Thermal Plaza Nursery in Thermal, California.