Have you ever wondered why blueberries appear blue at first but turn red when squished?
Now, scientists have figured out that big riddle.
The blue comes from within their waxy coats – and scientists have been able to harvest it to make a new blue coating that has never been seen before.
The finding applies to other fruits that are the same colour – including damsons, sloes and juniper berries, according to University of Bristol scientists.
The study, published in the journal Science Advances, shows why blueberries – and damsons, sloes and juniper berries – are blue, despite their dark red insides.
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 some birds.
They say the blue colouring arises when light bounces off the randomly arranged crystal structures of the epicuticular wax.
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 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.
‘It shows that nature has evolved to use a really neat trick, an ultrathin layer for an important colourant.’
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 waterproof, self-cleaning coating, but it’s only now they realise how important the structure is for visible colouration.
Now the team plan 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.
