How to Wash Blackberries to Remove Contaminants—and Keep Them Fresh Longer

Blackberries are in season from May through September, so there's plenty of time to bake cobblers and pies galore. But before you gather ingredients for a favorite recipe, you should know how to clean blackberries properly. As with other berries, the deep purple fruits are delicate, though not as fragile as raspberries, warranting a gentle hand. Blackberries also have many nooks and crannies that contaminants can easily hide in, making it extra important to wash them well.

Plus, blackberries are porous and high in moisture, making them particularly susceptible to mold growth. It doesn't help that the environment naturally contains mold spores, many of which thrive when exposed to the moisture in blackberries. However, with the correct washing methods, you can delay mold growth and make plenty of blackberry recipes (or at least freeze the berries at their prime) before summer's end. We spoke to food scientists to find out the techniques they recommend.

What to Know About Pesticides and Blackberries

Blackberries are not among the very top pesticide-contaminated fruits, says Bryan Quoc Le, Ph.D., food scientist and founder at Mendocino Food Consulting. "Fruits like strawberries, apples, and grapes typically rank higher due to their delicate skin and higher commercial demand, which often leads to more intensive pesticide use," he adds.

Even so, the USDA Pesticide Data Program shows 56 unique pesticides detected in their set of 338 samples. While detected residues were below EPA tolerance levels, it's still important to learn how to clean blackberries at home, especially if you frequently eat the juicy fruit.

How to Clean Blackberries

It's worth noting that no single washing method can remove 100 percent of pesticide residues from produce, says Kimberly Baker, Ph.D., RD, LD, director of the Clemson Extension Food Systems and Safety Program Team. And without laboratory testing, there's no way to verify if all the pesticide residues have been removed, she notes. 

Thus, the most important step you can take is to be informed about where your produce (in this case, blackberries) comes from. This is easier to do if you're buying from a local farmer, as you can ask how the produce is grown and what practices they use to meet food safety standards and manage pesticide residues, explains Baker. (Or, grow your own—you can even grow them indoors!)

When it's time to wash your blackberries, follow these methods for optimal results.

Under Running Water

"Washing produce in cool running water is the most widely recommended method," shares Baker. The flowing water will help carry away contaminants, including pesticide residues, dirt, debris, and microorganisms. Baker prefers this method over using a bowl if you're doing multiple rounds, because soaking berries in a bowl can "cause contaminants to linger in the water and transfer to other batches," she says.

Here's how to clean blackberries with running water:

1. Place the berries in a colander without overcrowding them. This allows water to flow freely over each berry, says Baker.
2. Rinse the berries under cool running water, ensuring the stream isn't too strong to avoid bruising or damaging the fruit.
3. Continue for about 20 to 30 seconds, recommends Le. 

Transfer the berries to a single-use paper towel to absorb excess moisture, says Baker.

Using Baking Soda

"Generally, washing blackberries under running water should be fine to remove traces of pesticides," says Le. This means using other solutions, such as baking soda, isn't necessary.

If you would like to use baking soda for peace of mind, follow the steps below. Studies have shown that the alkaline nature of baking soda helps break down pesticide residue.

1. In a large bowl, combine 1 teaspoon of baking soda for every 2 cups of water.
2. Add the berries. Carefully swirl them around for 15 to 30 seconds.
3. Rinse with cool running water.

Our experts say that cleaning blackberries with baking soda can negatively affect the taste and texture of the berries. This is even more likely if you use too much baking soda or soak the berries in the solution for too long.

How to Prevent Mold on Blackberries

As a perishable food, blackberries will eventually deteriorate and develop mold. But it's possible to delay the growth of mold by following these tips as you wash them. 

• Wash just before using: "Wait to wash the blackberries until you're ready to eat them," advises Le. Otherwise, any moisture left on the fruit can promote mold growth and spoilage, he says.  
• Dry well: If you must wash blackberries before storing them, make sure they are completely dry. "Keeping the berries dry helps slow mold growth, as moisture encourages mold development," says Baker.
• Store in the refrigerator: The cold temperatures of the refrigerate will inhibit molds that thrive in warmer conditions, says Baker. This can help further reduce the risk of spoilage, she adds.