I’m not sure if a chef is the best person to ask, but as you work with fresh ingredients, I thought I would ask. How can I get soft berries, such as raspberries and blackberries to last longer than 24 hours. It seems that they become mushy and moldy within a day of purchasing. Is there a way to store them that will allow them to last for a couple days more?
Fresh berries are particularly fragile and susceptible to spoilage. Rule # 1 is to never wash them before you’re ready to use them. Any moisture will cause almost instant mold and/or rot. Rule # 2 is to keep them refrigerated (can we have two first rules? Because this is just as important as Rule # 1.) Don’t leave them in your car on a hot day; bring an ice pack along if you think there will be any significant lag time between purchasing and bringing them home.
Once mold starts, it’s highly contagious, and you won’t always notice if it begins in the bottom of the container. It’s likely to begin at the bottom, too. Have you ever wondered why berry baskets are so shallow? It’s because layering them too deep tends to crush the ones on the bottom. Once they start exuding juice, the moisture will attract mold, even if you didn’t wash them.
Here’s what I recommend to minimize spoilage. Buy only what you’ll use up quickly, unless you plan to freeze the excess. Pick over the berries and discard any bruised or damaged ones, leaves, insects, etc. Don’t rinse or wash them! And don’t trim berries like strawberries; this obviously isn’t a concern with blackberries, raspberries, or blueberries. Place a layer of paper towels on a baking sheet or large platter, and spread the berries out so they’re not touching each other. (You don’t need the paper towel layer if you’re working with blueberries.) Lightly cover with plastic wrap – don’t tuck one side of the wrap, as you don’t want to collect moisture under it. You should be able to find room for a baking sheet in the fridge by balancing it top of other items.
I’ve found that if the berries are in good condition when you purchase or pick them, they should keep for a few days. The sooner you consume them, though, the better. They don’t continue to ripen once picked, so they won’t improve with keeping.
If you find yourself with a glut of berries, follow the above guidelines, but put the baking sheet in the freezer for an hour or so. Once the berries are frozen, working quickly, pour them into a freezer bag, remove as much air as possible, and get them back in the freezer. This approximates the IQF (Individually Quick Frozen) method the commercial companies use, and avoids the problem of a big frozen clump of berries all stuck together. You can now pour out only what you want to use at one time and keep the rest for another time.
There are two other methods I’ve read about. One is to rinse berries in a mix of vinegar and water when you get them home. The other is to put them in hot water, 120°F to 140°F, not sufficiently hot to start cooking them. Both are said to kill any mold spores which would start decay, and it sounds good in theory. Because it’s difficult to dry them sufficiently after either of these treatments, though, I haven’t tried and thus can’t recommend them. My system works for well enough for me.