Carrots are orange because they absorb certain wavelengths of light more efficiently than others. Beta-carotene is the main pigment and is mainly absorbs in the 400-500nm region of the visible spectrum with a peak absorption at about 450nm. Carotenoids are one of the most important groups of natural pigments. They cause the yellow/orange colours of many fruit and vegetables. Though beta-carotene is most abundant in carrots it is also found in pumpkins, apricots and nectarines. Dark green vegetables such as spinach and broccoli are another good source. In these the orange colour is masked by the green colour of chlorophyll. This can be seen in leaves; in autumn, when the leaves die, the chlorophyll breaks down, and the yellow/red colours of the more stable carotenoids can be seen.
However, the properties of beta-carotene are not what prompted me to make this blog. Last night I was watching the 4th in the series of Christmast Lectures by Prof Sue Hartley – the Royal Institution Christmas Lectures are a series of lectures given by a prominent scientist each year to an audience of children and broadcast on TV – http://www.rigb.org/registrationControl?action=home.
Prof Hartley’s lecture was about selective breeding and how humans had used this technique of thousands of years to make food safer and easier to eat. The section about wheat was particularly good.
However, she also talked about the colour of carrots and said that not all carrots are indeed orange at all. They come in many varieties including white and purple.
Prof Hartley said that it was the Dutch who selectively bred wild (white) and cultivated (purple) carrots to create the orange ones that we all know today. The orange was popular because it is the Netherland’s national colour and, at the time, the Dutch were fighting for independence. It was this story that has led me today – yes, Christmas Day – to make a virtiual visit to the British Carrot museum to research this story. You can follow my tracks at – http://www.carrotmuseum.co.uk/. Yes, such a place really does exist! 🙂
It turns out the story is not so clear as that told by Prof Hartley (though I am sure she is aware of this and was simply making it interesting to the children). Certainfly the first cultivated carrots – in the Afghanistan region – were purple and orange carrots were cultivated in Northern Europe about 500 years ago. However, some scholars dispute the Dutch story about breeding orange carrots because orange was the national colour. Indeed, there is, apparently, a Byzantine manuscript from as long ago as 512AD that depicts orange carrots. So the mystery deepens and I have far better things to do on Christmas day than to research this further. Perhaps if any experts in carrot technology come across this page they can add an informative footnote?