Dr Michelle Dickinson: nanotechnologist reveals blueberries aren't actually blue

This week's topic is all about blueberries and how they aren't blue!

Have you ever wondered why blueberries look blue on the outside, but when you squeeze them, their juice is reddish-purple?

Well wonder no more, as scientists have just made a new discovery and found that blueberries are actually not blue at all, but instead trick us with a secret UV coating on their skin that makes them appear to be blue.

Published in the journal Science Advances, the researchers removed the thin wax coating naturally found on the skin of blueberries and found that it was made up of tiny structures that scatter both blue and UV light while absorbing other colours of light - when combined with the dark red juice inside the berry, this makes the outside of the berries appear blue, even though they don't contain any blue pigment at all.

So why would this coating exist?

Well, many visually guided animals that eat mostly fruit have eyes that are highly adapted for blue sensitivity. The colour blue, however, is very rare in nature due to there not being a true blue pigment in the natural world.

This waxy adaptation is a great trick that makes the blueberry more visible to fruit eating animals and therefore more likely that the berries and their seeds will be eaten.

The researchers found that the same trick is also performed by other fruits, including damsons and juniper berries.

The study has led to the researchers looking at ways of replicating the coating to create a new type of biocompatible and potentially edible UV and blue-reflective paint.

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