One of the best parts of summer is the fresh produce: corn and zucchini for grilling, juicy peaches and watermelon, and, of course, blueberries, one of the season's most quintessential fruits. There are endless ways to enjoy blueberries. Eat them by the handful, toss them in summer salads, sprinkle them over yogurt, or bake them into pies and muffins. Not only are they especially plump and juicy in the summer when they're in season, but they're typically cheaper during this time, too.
But what happens if you open the fridge and realize one berry is covered in mold? Does that one moldy blueberry ruin the whole pint?
To help determine whether your non-moldy blueberries in the same pint are safe to eat, we enlisted the help of two food experts: Bryan Quoc Le, Ph.D., founder and principal food consultant at Mendocino Food Consulting, and Emilie Symons, chef-instructor of Plant-Based Culinary Arts at the Institute of Culinary Education.
Here's their advice on moldy berries, along with tips for storing your berries so they last.
What Causes Mold Growth On Berries?
We've all been there—the berries you bought appeared mold-free, but only a day or two later, you find fuzzy fungi in the clamshell. What happened?
Although you can't see them, microscopic mold spores are present everywhere in the environment, both inside and outside your home. They can attach themselves to items and food, such as berries. "When conditions are ripe, the spores become active," Quoc Le says. As berries grow, he says, enzymes break down the berry's tissues, allowing the mold to accumulate nutrients and release more spores. This creates mold that is visible to the naked eye.
Environments that are humid, warm, and damp can encourage mold growth. That's why it's important to refrigerate blueberries after a trip to the grocery store or farmers' market.
What To Do If A Pint Of Blueberries Has Mold
The USDA offers a guide for handling food with mold and has different recommendations for hard and soft produce. Firm produce with low moisture, like cabbage and bell peppers, with small mold spots, can be used as long as you cut off at least 1 inch around the mold.
However, the USDA recommends discarding soft produce with high moisture content, such as peaches, cucumbers, and berries, as they can be contaminated below the surface.
But what if only one blueberry has mold? "There's no problem with eating a pint of berries if there's only one moldy berry," Quoc Le says. "However, if the mold has infected a large proportion of the pint, where several berries are covered in mold, it's best to throw away the berries."
Symons offers similar advice if you spot one moldy berry: "I just pick it out and remove any affected neighboring berries so the whole container doesn't spoil."
Tips For Buying & Storing Blueberries
When shopping, Quoc Le recommends avoiding berries that are soft, damaged, or contain any mold, as they can harbor microorganisms. Typically, they won't make you sick, but he says they can cause issues for those who are allergic to mold or have a compromised immune system.
Once you bring your berries home, store them in the refrigerator to extend their shelf life. Both experts say not to wash them until you're ready to eat them. "Washing them increases moisture and encourages the growth of mold," Quoc Le says.
He notes you can also wash berries in a vinegar-water solution. As described in our guide on how to clean strawberries, we recommend soaking berries in a solution of 3 parts water to 1 part white vinegar for 15 to 20 minutes to help reduce mold growth. Rinse thoroughly and dry with a soft towel before storing.
