Scientists Finally Discover Why Blueberries Are Blue

Food & Wine ^ | March 8, 2024 | Stacey Leasca

[nickcarraway]

Sometimes, life throws you such a great fun fact you simply must share it with the world. This week, it's the fact that blueberries aren't actually blue. They just appear that way. And scientists just revealed how and why.

In a study published in February in Science Advances, researchers from the United Kingdom shared their findings on why blueberries and other blue-hued fruits appear to be that color to the human eye despite having a dark red hue on the fruit skin. (Think about if you mashed up a bunch of blueberries into a juice. That juice would be a deep reddish-purple, not blue.)

"Blueberries are observably blue; however, the pigments found in blueberries are not," the study succinctly begins. So, why do they appear this way? As the findings state, it's all thanks to the "epicuticular wax" coating, which the scientists called a "really neat trick" of nature.

Our Best Blueberry Recipes to Make This Summer According to the authors, the blue appearance is "dominated by scattering from the random assembly of nonspherical particles," which they found after looking at the very thin layer of the wax under a microscope. These particles can scatter blue and UV light, making the berry appear blue to humans but, perhaps more importantly, to birds and other animals that see UV light, who may come and eat the berries and spread the seeds. (The authors note in the study it is "not clear whether UV itself enhances attraction to birds" but that "it is clear that the UV reflectance is visually salient to some birds.") And truly, when we say "very thin layer," we mean it. As Popular Science noted about this study, the substance is so thin it's smaller than a strand of human hair.

The wax, the authors note, has a variety of functions in nature that are well documented. (This is different from a wax coating put on fruits by manufacturers to protect them from damage and moisture loss prior to being sold.) But what this new study does is show just how important that wax is for the coloration of fruit. And now, because this team has unveiled the structure, future scientists may one day be able to recreate the coating and use it for a host of applications, including, as the University of Bristol pointed out, "more sustainable, biocompatible and even edible UV and blue-reflective paint."

"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 Middleton, a physicist and co-author of the study, shared in a press release. "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."

[takebackaustin]

Mommy/Daddy, why is the sky blue?

For the same reason the sun is redder at sunset, and blueberries look blue.

Blue light is preferentially scattered to the side (In air, Raleigh scattering. ). When you look at the sky, you see the sunlight that was scattered to the side. That’s also why the sun looks redder in the morning and evening - the length of air the light passes through is longer at a low elevation over the horizon. The red tends to goes straight through and the blue tends to be scattered more. In a blueberry, the red goes on in and is absorbed, more blue is scattered and makes it back out.

The time has come,' the Walrus said, To talk of many things: Of shoes — and ships — and sealing-wax — Of cabbages — and kings — And why the sea is boiling hot — And whether pigs have wings.' ,