Unraveling Nature’s Blue Secret: The Hidden Brilliance of Blueberries and Beyond

In a revelation that challenges conventional wisdom, scientists at the University of Bristol have uncovered the secret behind the luscious blue hue of blueberries and other dark-fruited delights. Contrary to popular belief, it’s not the fruit’s pigmented flesh that imbues it with its captivating color, but rather, a microscopic layer of wax coating that cloaks its surface.

Published in Science Advances, the study unveils the intricate mechanism responsible for the enigmatic blue tint of blueberries, damsons, sloes, and juniper berries. This captivating hue, which appears blue to human eyes and blue-UV to avian vision, emerges from the interaction of minute crystal structures within the fruit’s epicuticular wax with light.

Rox Middleton, a Research Fellow at Bristol’s School of Biological Sciences, elucidates, “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.”

By meticulously dissecting the wax coating and re-crystallizing it, the researchers succeeded in recreating a novel blue-UV coating, a mere two microns thick, with remarkable reflective properties. This breakthrough not only sheds light on nature’s ingenious coloration mechanisms but also holds promise for the development of innovative colorant technologies.

“It shows that nature has evolved to use a really neat trick, an ultrathin layer for an important colorant,” Rox emphasizes.

Eager to harness this newfound knowledge, the team aims to explore simplified methods for reproducing and applying the wax coating. This endeavor could pave the way for sustainable, biocompatible, and even edible UV and blue-reflective paints, mirroring the multifunctionality of natural biological coatings that safeguard plants.

“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,” Rox reflects. “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.”

As researchers endeavor to integrate the functionality of natural wax coatings into engineered materials, they embark on a journey toward unlocking nature’s blue secret—a quest fueled by curiosity, innovation, and the boundless potential of biomimicry.

More information: Rox Middleton et al, Self-assembled, Disordered Structural Color from Fruit Wax Bloom, Science Advances (2024). DOI: 10.1126/sciadv.adk4219. www.science.org/doi/10.1126/sciadv.adk4219