There’s a strange reason why blueberries have their distinctive colour

Ever wondered what makes blueberries the lovely colour that they are? And damsons, sloes and juniper berries? Would you believe it’s down to their wax coating?

Despite having dark red colour pigments in the skin of the fruit, researchers have now shown why blueberries appear blue to us.

This is all down to a layer of wax that covers the fruit made up of ­miniature crystals that scatter blue and UV light.

Rox Middleton, research fellow at Bristol’s School of Biological Sciences, explained: “The blue of blueberries can’t be ‘extracted’ by squishing them because it isn’t located in the pigmented juice that can be squeezed from the fruit.

“That was why we knew that there must be something strange about the colour. So we removed the wax and re-crystallised it on card, and in doing so we were able to create a brand new blue UV coating.”

The ultra-thin colourant is around two microns thick, (a hair is about 80 microns) and although less reflective, it’s visibly blue and reflects UV well, possibly paving the way for developing new ways to make colour.

“It shows that nature has evolved to use a really neat trick, an ultra-thin layer for an important colorant,” Rox added.

This also helps make the fruit visible to birds which eat them and thereby distribute seeds. Most plants are coated in a thin layer of wax which has multiple functions, many of them still not understood by scientists.

They know that the wax can be a very effective at self-cleaning and also acts as a water repellent.

However, until now researchers didn’t know how important the wax was for visible coloration. The team now plans to look at easier ways of recreating the coating and applying it. This could lead to a more sustainable, biocompatible and even edible UV, and could also be used to create blue reflective paint.

Furthermore, these coatings could have the same multiple functions as the natural ones that protect plants.

Rox Middleton added: “It was really interesting to find that there was an unknown coloration ­mechanism right under our noses on popular fruits that we grow and eat all the time.

“It was even more exciting to be able to reproduce that colour by harvesting the wax to make a new blue coating that no one’s seen before. Building all that functionality of this natural wax into artificially engineered materials is the dream.”

I eat blueberries by the handful and I’m wondering if that wax is particularly good for us too.