What makes blood oranges red

The distinctive red colouring of blood oranges is due to the presence of naturally occurring pigments called anthocyanins. Raspberries, blueberries and black rice are amongst the most common foods where we find anthocyanins. They are very common to many flowers and fruits but just not in citrus.

The flesh develops the red colouring when the fruits are subject to low night time temperatures. This is the same way that the skin of lemons turn from green to yellow. Nutritionists believe that anthocyanins have anti-inflammatory properties that help prevent cancer, bacterial infections, diabetes and reduce the risk of heart disease. They also help defend blood vessels from oxidative damage and reduce the accumulation of LDL cholesterol. CREA, the Council for Agricultural Research and Economics, has been working on a study to enhance the genetic biodiversity of blood oranges.

Their aim is to not only enhance their taste, but their health properties as well. CREA experts explain: the skin can be treated by extract taken from the blood orange and byproducts of citrus processing. Tests were conducted on the skin to demonstrate the photo-protective effect in the treatment of erythema caused by UV lamps. Another study found that the extract from blood oranges contained anti-inflammatory activity and plenty of antioxidants.

These antioxidants and other active ingredients protect the body from the effects of free radicals. Free radicals are unstable molecules that promote the development of many degenerative diseases and early aging of the skin. Large amounts of free radicals form when the body is exposed to cigarette smoke, drugs, pollution, strenuous exercising, toxic wastes and UV radiation.

And what's anthocyanin? It's a class of "universal plant colorants responsible for the red, purple, and blue hues evident in many fruits, vegetables, cereal grains, and flowers," write researchers Izabela Konczak and Wei Zhang in the Journal of Biomedicine and Biotechnology. In addition to making the inside of a blood orange look like a ruby, anthocyanin also gives raspberries and blackberries and even darker red tomatoes their purple and blue tones.

But anthocyanin does more than affect the color of fruits. Anthocyanin adds to the nutritional value of the fruit since is a type of flavonoid, also known as an antioxidant. There's some compelling scientific evidence that consuming these antioxidants in fruit like blood oranges can help prevent damage on a cellular level.

And regular oranges just don't have the same high levels of antioxidants as blood oranges—so if you're looking to get your flavonoid on, you're better off reaching for a jewel-toned blood orange instead.

Blood oranges also have a slightly different taste than navel oranges or even common oranges that you'd squeeze into juice. While a sweet orange is mainly sweet, the taste of a blood orange is a bit more complex, and as McGee writes, it "combines citrus notes with a distinct raspberry-like aroma. But when it comes to eating blood oranges, it's like eating any other orange.