What You Should Know About Baking With Frozen Blueberries
Especially when fresh blueberries aren't in season, a bag of frozen blueberries is an easy, affordable way to add some fruit to your baked goods. But you don't necessarily want to pour them straight from the bag into your batter — for one thing, anyone who's bought frozen blueberries (or any frozen fruit) before knows that as they thaw, you end up with quite a bit of bright purple-ish red liquid as any ice crystals from the freezer melt away. Plus, frozen berries are usually heavier than your batter, and they can easily all sink to the bottom of a cake.
Luckily, with a few tricks up your sleeve, you can avoid these common baking mistakes. You don't have to end up with a cake or bread that has all of the berries clustered at the bottom. According to the U.S. Highbush Blueberry Council, lightly coating your blueberries in cornstarch or flour will help prevent them from sinking. Just pour your berries in a bowl, add a little flour or cornstarch, and stir or toss to coat them before you bake. Another tip from the Council is to layer the berries through the batter — pour half of your batter into the baking pan, then add half the berries, then pour on the last of the batter, and sprinkle the final berries on top.
How to prevent your batter from turning blue when using frozen blueberries
Another peril of baking with frozen berries is that they can change the color of your batter, with the result being a sickly-looking blue-ish green cake, muffin, or bread. But according to the King Arthur Baking Company's website, you can avoid this (or at least cut down on the color change) by rinsing frozen blueberries before mixing them into your batter. King Arthur recommends rinsing them in cold water a few times until there's noticeably less color in the water. Then, dry off the berries with a few paper towels before adding them to your batter.
Betty Crocker's website also recommends a similar method for prepping frozen blueberries for baking. However, they note that you can thaw the berries in a strainer over a bowl, and add any juices that are left behind to a smoothie. Once they're thawed, dry them off with a paper towel and coat in flour (Betty Crocker's site also notes that coating the berries in flour can help prevent the batter from changing color). You don't have to do much to get frozen blueberries ready to bake, but just a little prep will make your muffins that much better.