Scientists discover what makes blueberries blue

By Stephen Beech via SWNS

Blueberries get their distinct coloring from tiny structures in their wax coating, reveals new research.

And scientists have been able to harvest it to make a new blue coating no one has seen before.

The same applies to other fruits that are the same color - including damsons, sloes and juniper berries, according to University of Bristol scientists.

Their findings, published in the journal Science Advances, show why blueberries really are blue - despite the dark red color of the pigments in the fruit skin.

The blue colour is instead provided by a layer of wax that surrounds the fruit which is made up of miniature structures that scatter blue and UV light.

The team explained that it gives blueberries their blue appearance to humans and blue-UV to birds.

They say the chromatic blue-UV reflectance arises from the interaction of the randomly arranged crystal structures of the epicuticular wax with light.

Dr. Rox Middleton, Research Fellow at Bristol’s School of Biological Sciences, said: “The blue of blueberries can’t be ‘extracted’ by squishing – 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 color.

“So we removed the wax and re-crystallized it on card and in doing so we were able to create a brand new blue-UV coating.”

She explained that the ultra-thin colorant is around two microns thick, and although less reflective, it’s visibly blue and reflects UV well, possibly paving the way for new colorant methods.

Dr. Middleton said: “It shows that nature has evolved to use a really neat trick, an ultrathin layer for an important colorant."

The researchers say that most plants are coated in a thin layer of wax which has multiple functions, many of which scientists still don’t understand.

They know that it can be very effective as a hydrophobic, self-cleaning coating, but it's only now they realize how important the structure is for visible coloration.

Now the team plans to look at easier ways of recreating the coating and applying it.

They say it could lead to a more sustainable, biocompatible and even edible UV and blue-reflective paint.

And the coatings could have the same multiple functions as natural biological ones that protect plants.

Dr. Middleton said: “It was really interesting to find that there was an unknown colouration 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 color by harvesting the wax to make a new blue coating that no one’s seen before."

She added: “Building all that functionality of this natural wax into artificially engineered materials is the dream.”