How can the outside of a berry be blue? You might think that berries use (simple) dyes. Research now shows that it uses a trick that even science would envy.
It seems like a simple question: How can blueberries be? However, scientists have been wondering about this for some time. Scientist Rox Middleton contributed to the research. “You can’t get the blue color out of a berry by pressing too hard, for example,” she explains. “This is because the blue color is not present in the colored juice. We knew there had to be more.” The colored berry juice is not blue at all; It is more towards a dark red color. What does it look like? Berries get their blue color from special crystalline structures in the waxy layer surrounding the berries. These structures are 0.002 mm thick and reflect visible blue light and invisible UV rays. The research has been published in the journal Advancement of science.
Wax layer
Middleton’s team made this discovery by carefully removing the wax layer from the berry and then allowing it to recrystallize in the laboratory. “After removing the wax layer, we placed it on card and then let it crystallize again,” explains Middleton. “Eventually, we were able to develop a new paint that reflects the same colors as the berries.”
Just a reminder: Light is essentially a collection of light particles that “move” through space at different frequencies. Some photons vibrate more strongly than others and therefore show a different color. Some of these colors fall within the visible light spectrum, but not all. For example, ultraviolet (UV) and infrared (IR) rays standardly lie outside the light spectrum visible to humans. It often happens that photons of different frequencies react differently when they collide with an object: some photons are absorbed, while others are reflected. This is what actually happens with blueberries: blue and UV light are reflected, while other colors are absorbed.
Edible paint
However, there is a lot to be said for the wax layer that surrounds blueberries. For example, the vast majority of plants have a very thin waxy layer over their leaves. Scientists have known for some time that this layer is particularly water repellent and self-cleaning. Now Middleton’s team has discovered there’s an added bonus: “Our research shows that nature has developed a particularly cool trick; a very thin layer that can reveal a bright color. And perhaps most importantly: scientists can now replicate this trick.”
The research team is now working on possible applications of the new technology. It is quite far-reaching: a new coating could also be developed that uses the wax layer principle. The research suggests that it should therefore be possible to develop a type of paint that is more environmentally friendly – and edible too. Not only that; The new type of coating also inherits other properties of the wax layer, such as strong water resistance and self-cleaning property. “It was very surprising to discover a completely new way to color something so ordinary: a kind of fruit that people eat every day,” Middleton concludes. “Developing a synthetic material that can imitate all these natural functions is ultimately our dream.”
