While many fruits come and go—just try to get a juicy peach in the northeast in the dead of winter—grapes are reliable year-round. They’re a fridge staple for afternoon snacks, nonalcoholic spritzers, and even sheet-pan chicken. And if you snag them at the supermarket as often as we do, you’ve perhaps also noticed something odd—a powdery coating on the skins. What is that white stuff?
In disarray, hole-filled plastic bag in hand, you briskly turn to the internet. Maybe it’s a scatter of dust, blotches of mold, or a showering of pesticides. But no, it’s none of the above. So what is it? Well, it’s absolutely safe to eat. But to demystify this white stuff once and for all, I spoke to viticulture extension specialist Hans Walter-Peterson of Cornell Cooperative Extension to get answers.
What is that white stuff on grapes?
The waxy white coloration on grapes has a name. “It’s what we call bloom, which is different from what flowers do,” explains Walter-Peterson. Bloom covers the grape’s outer layer (what’s unfortunately known as the cuticle) and often includes yeast. The yeast appears from the air (yes, it’s just floating around you right now) and will collect onto the skin.
Bloom can protect grapes, like a windbreaker on a breezy day. “It helps to shed water to some extent, and it’s a bit of a barrier for pathogens. There is some water evaporation from the grape berry as it matures, so bloom helps the grape from drying out too fast,” says Walter-Peterson.
Of course, the bloom can’t shield grapes forever. “Eventually, that covering will break down,” says Walter-Peterson, “and the grapes will naturally dehydrate and shrivel as they age.”
Does this happen with other fruits?
Plenty of fruits have a light white dusting on them—think apples, pears, plums, blueberries. You might be able to notice the cloudy outer layer as you’re picking the fruit from a tree or bush.
Is it bad if my grapes don’t have any bloom?
Because visible bloom can be easily wiped off with your finger, it’s no big deal if the bunch you bring home from the grocery store seems bloom-less.“If there are a bunch of grapes in a box being shipped and they jostle around and rub each other, some bloom might rub off,” Walter-Peterson says. So don’t rely on bloom alone as an indicator of freshness. Also look for firm, plump grapes with verdant, flexible stems.
Can I eat the bloom on grapes?
For sure. If you eat grapes, you also likely eat bloom. It’s naturally occurring, food-safe, and harmless. Which means the only thing left to do is make that sheet-pan chicken.
Grape Stuff
Nina Moskowitz is an editorial assistant at Bon Appétit and Epicurious, supporting the editor in chief, editing print stories, and solving cooking mysteries (like why do beans make us fart?).