Making Blood Red Oranges

?Blood oranges with their deep red interiors were first observed as a mutation of regular sweet oranges in Italy way back in the 1600s.

Since then, citrus growers have learned that the "blood" color of blood oranges is due to anthocyanin pigments in the fruit and that those pigments will not be produced in significant amounts unless the fruit is exposed to very cold or frosty conditions during its development or post-harvest period. No cold exposure means very little anthocyanin will be produced and blood oranges will not mature to their full red color.

Just like many other anthocyanin-rich foods, blood oranges deliver a variety of health benefits thanks to the vitamin C, fiber, and carotenoids they contain. However, blood oranges with their high anthocyanin content also provide additional antioxidant benefits, making them one of the most healthful citrus fruits grown today.

Unfortunately, the successful production of healthful blood oranges has been limited outside their major area of production in Sicily, and today worldwide availability is quite limited. Blood oranges could be grown successfully in more areas of the world if researchers knew exactly why the exposure to the correct cold temperatures causes anthocyanin production.
Because both the citrus agriculture industry and human health could benefit from the ability to grow blood oranges successfully in more locations, an international research group at the John Innes Center in the U.K. decided to try to determine why blood oranges develop anthocyanin pigments.

It didn't take long for the group to discover a regulator gene in blood oranges that increases the expression of anthocyanin-encoding genes. Indeed, when expressed in tobacco, Ruby produced red leaves by increasing anthocyanin. What they learned was that the regulator gene called "Ruby" is produced in very high levels in blood oranges in direct correlation with the amount of anthocyanin present in the fruit, and not surprisingly, so-called "normal" blonde oranges do not express the "Ruby" gene at all.

The recent work of the U.K. researchers in determining the mechanism that causes cold temperatures to produce the rich red color of blood oranges is a big step toward more reliable worldwide production and increased future availability of the health-packed little oranges.

Among the future possibilities is the hope that less cold-dependent blood oranges could be created by genetic engineering, and that could lead to more blood orange production in existing "normal" citrus growing areas and increase the supply of healthier orange juice worldwide.