What’s the white film on blueberries?

What you see: A whitish film on your blueberries.
What it is: A naturally occurring protective coating called bloom. 
Eat or toss: Eat!

That silvery film on the outside of your blueberries is supposed to be there. 

It’s called “bloom” and is similar to the whitish coating you see on plums and grapes. In all cases it’s a waxy substance that helps seal in moisture, protect the fruit from decay, and extend its shelf life.

While the bloom can help stave off tiny invaders, it comes off easily. That’s why berries on a bush will have a more uniform whitish coating, while berries in a store-bought pint will have a blotchier coat of bloom. As harvesting, sorting and packing by machine jostles the berries around, the bloom easily rubs away.

Mark Longstroth, a retired small fruit educator at Michigan State University Extension, says that based on the amount of bloom he can tell how a pint of berries was picked. 

“I can look at the fruit and the package and go ‘Oh that was harvested by a machine,’” he said. “As it gets handled or it bumps against things and rolls over things that bloom gets rubbed off.” 

Researchers have found that removing the bloom not only shortens shelf life, but can also diminish the berries’ flavor and antioxidants. 

Go about one minute and 20 seconds into this video and you’ll see just how easy it is to rub off some of that bloom!

You may also see a berry’s bloom referred to as the “cuticle” or as “cuticular wax.” In fact, all plants have some form of a cuticle that coats and protects their vulnerable above-ground parts. Sometimes it’s simply more visible than others. And, moving beyond the plant kingdom, it’s worth noting that even eggs have a protective bloom. In the U.S. it’s washed off (along with debris clinging to the egg), but other countries leave it on. More in this post about refrigerating eggs.