The social media posts haunted me. They featured photos of bright berries and grapes stacked in darling Mason jars, or cutesy illustrations of jars packed with strawberries.
“Old me!” the posts declared, showing a grocery store clamshell of berries. Next to that, the phrase “New me” and a beautiful image of berries in tightly sealed jars.
I was skeptical. It seemed to me that this would trap the water that naturally evaporates away from fresh produce over time, leading to wet fruit. And I wondered if the berries, which like all fresh produce are alive and respiring, would use up all the oxygen in the jar, which could only create more problems.
But the posts just kept showing up in my feeds and they were getting hundreds, sometimes thousands, of likes and comments, and it just didn’t make sense to me. So, I pitched a story to The Washington Post about exploring the safety of “pretty jar storage hacks” (read that story here) and did some of my own experimenting.
I didn’t have room in the WaPo story to detail my berry experiments, so I’m dishing on the details here. Here’s what happened when I attempted to follow a number of berry storage “hacks”.
Materials and set up: Three types of berries, four storage methods
I bought three kinds of berries: blueberries, raspberries and strawberries.
I stored them four different ways, based on various “hacks”:
- In the original clamshell (control group).
- Transferred directly from the grocery store clamshell to a sealed jar.
- Rinsed, then laid out to dry, then placed in a jar.
- Dunked in a vinegar solution, then rinsed and dried in a towel-lined salad spinner and stored in a napkin-lined container with a loose-fitting lid.
Setting up the storage systems
Challenge 1: Oops, the strawberries were already moldy
Of course, as soon as I got started, I encountered some issues. One of the strawberries in the clamshell I purchased was moldy, increasing the odds of mold forming on the others. I did my best to remove it and any berries that looked possibly exposed and kept going, knowing that mold spores were probably circulating in my strawberries.
(By the way, this is one of the many things that frustrates me about these “hacks”–they ignore the fact that every berry has a different microbial story. A strawberry that already has some mold spores on it, which is possible even before you see fuzz, is going to have a shorter shelf life than one that doesn’t, no matter how you store the berries.)
Challenge 2: “Rinsing” and air drying is easier said than done
First things first: a quick rinse of your berries before you eat them is always a good idea. It’s an imperfect way to clean your fruit, but it will get some things off of it.
But, but but… as I wrote in this article about the problems with berry storage hacks, rinsing berries before storing them is usually problematic. The water can spread microbes around. Rinsing also provides the moisture microbes need to decay berries. Further, drying the berries after rinsing requires that they spend more time at room temperature, which shrinks their shelf lives. The longer berries spend at room temperature, the shorter their shelve lives will be.
Still, this is what the hacks were suggesting, so I tried rinsing the berries. The ones that I laid out on the counter to dry were frustrating because they never dried completely, and well, I needed to get on with my day. Since raspberries are shaped like teeny tiny cups, it was easy for water to be trapped inside them. I found the spaces in between the leaves and top of the strawberry also took forever to dry. Eventually I gave up on waiting, concluding that my experiment needed to reflect the practicalities of real life and not pristine lab conditions.
Vinegar rinse: Choose between using a lot of vinegar or dunking repeatedly in the same bowl of vinegar solution
For the more elaborate vinegar rinse, I made a solution of 3 parts water to 1 part vinegar, dunked the berries in, then rinsed them with water and dried them in a salad spinner lined with cloth napkins (the guidance said paper towels, but I try not to use too many single-use items so cloth napkins it was). This was all according to guidance from America’s Test Kitchen.
But as I was doing this, I already saw reasons to be concerned and frustrated. Truly rinsing with the vinegar solution would send an impractical volume of vinegar down the drain, so I opted to dunk the berries in a bowl of my vinegar solution and then rinse under the faucet. Then, I had to confront whether I needed a new batch of vinegar solution for each type of berry. I concluded that would be wasteful, but it also increased the odds of consolidating the microbial load with every batch of berries I processed through it. Meanwhile, multiple scientists told me that vinegar was unlikely to be potent enough to significantly resolve microbial concerns.
Salad spinner dry: effective, but generates more dishes
The salad spinner drying method was surprisingly effective, though still didn’t get the berries perfectly dry. After the drying step, their instructions were to “Store the berries in a loosely covered paper towel–lined container at the front of the fridge.” So, this batch didn’t go in a sealed jar, but rather a squat deli container lined with a cloth napkin with the lid slightly ajar.
The vinegar rinse method was definitely the most involved and time consuming. And it left me with several large dirty dishes, not the best.
In the end, I had twelve different containers of fruit. The experiment was on. I left them in the fridge, untouched, for about 10 days while I was out of town.
About 10 days later…
When I came home from vacation, here’s what I found:
Every jar was coated with condensation on the inside; those berries were also more wet. The berries that had been rinsed and jarred had the most water. The vinegar-rinsed berries stored in containers with a napkin liner and a loose fitting lid were in the best shape, with the exception of the strawberries. The berries still in the original containers varied in how OK they still were.
The strawberries
In jars (both rinsed and not rinsed):
Smelled intensely when I opened the jar. Somewhere between nail polish remover and rubbing alcohol. This tracks with what Elizabeth Mitcham, an emeritus professor in postharvest science at the University of California, would later tell me – the berries, she predicted, could deplete the oxygen in the jar within days. Once that happened, they would switch to anaerobic respiration to produce energy to run their cells. Anaerobic energy generates various chemicals, including alcohols, as byproducts, giving berries off flavors and smells.
The strawberries were, however, still plump. This also makes sense; the jar trapped moisture making the air humid and less likely to pull water from the berries.
The jarred strawberries also did not develop any mold. This also tracks – mold will not grow as well in high-carbon-dioxide environments, Mitcham told me.
Vinegar rinsed, spindried, placed in cotton-napkin lined container with the lid ajar:
The strawberries that had been vinegar rinsed and dried and then placed in a cotton napkin lined deli container were very moldy.
Original container
These strawberries shrank (due to water loss) and developed mold.
Summary: After about 10 days, regardless of the storage method, none of these strawberries were good to eat. Problems ranged from off-flavors to mold. These strawberries were arguably more at risk of mold because one of the berries in the original package was moldy.
Conclusions: If you can keep your strawberries in a humid environment, they’ll stay plumper longer. If you can also reduce the oxygen that reaches them, perhaps by only having a small opening in the container, that can also help, but they need some oxygen to prevent their cells from resorting to anaerobic respiration and thus producing off flavors. Eat your strawberries ASAP and don’t mess with storage hacks!
The raspberries
In jars
Smelled intensely when I opened the jar, not necessarily off-putting, but not normal either. The jars were wet inside, particularly the jar of pre-rinsed berries, where water mixed with raspberry juice accumulated at the bottom. That juice signals that some cells were busting open, which can happen more easily if berries are stressed (running low on oxygen supplies in a tightly sealed jar counts as berry stress!). Thin berry skin can also absorb water, not in a hydrating way, but in a way that can block channels for air circulation within the berry and lead to more anaerobic respiration and its associated odors and flavors.
Vinegar rinsed in cloth napkin-lined container
These were the most passable, though, some berries had spilled some juice, which had dried into a stain on the napkin. I still found I wasn’t so enthusiastic about eating them. I think the storage container was central here; I suspect they would have fared just as well without the vinegar rinse.
Original container
Smaller, shriveled, darker in color. This makes sense because the original container had the most air openings and therefore the most avenues for water loss. Less water means the cells are less plump. If the cells are less plump the fruit is less plump.
Summary: The jarred raspberries got more and more intensely smelling as time went on. The ones stored in breathable containers fared better, though the ones in the clamshell shriveled and shrank as they lost water over time. I suspect the moisture-absorbing napkin and the slightly open container trapped humidity, but still allowed for air flow—this, I believe, was key to keep the vinegar-rinsed batch in good shape. Based on conversations with scientists, I am skeptical that the vinegar rinse helped, but I can’t rule it out.
Conclusions: To stretch the life of your raspberries, put them in a napkin-lined container. Leave the container slightly open to trap humidity, but still allow for air flow. Don’t rinse them before you store them.
The blueberries
In jars
Aside from the condensation on the inside of the jar, these looked the same as when I put them in. This makes sense. Blueberries respire, and therefore age, slower than other berries. Their thicker skins also slow water loss. So they’ll last longer no matter what. Still, the water in the jar creeped me out.
Vinegar rinsed in cloth napkin-lined container
These seemed OK.
Original container
These seemed OK.
Summary: All of the blueberries seemed fine, suggesting that none of the extra effort was needed. Though, I’d rather not eat “wet” berries and so, for a number of reasons, I wouldn’t store them in sealed jars in the future.
Conclusions: Blueberries naturally have longer shelf lives than thinner skinned and faster respiring raspberries and strawberries. Given that condensation forms inside a jar, that blueberries already have longer shelf lives, and that jar storage creates a dicy anaerobic environment, I see no benefits and only problems with this jar hack: hard no. For the 10 days I was away, there wasn’t much added benefit from the vinegar rinse and cloth-lined ajar container storage method. However, in the future if I had a large load of blueberries to store (from a picking expedition, for example), I would consider storing them in a cloth napkin-lined container with a lid left ajar.
Overall takeaways
These storage hacks usually aren’t worth your time! I go into more detail about the problems with jar-oriented storage hacks in this article but the best approach to getting the most shelf life out of your berries is to eat them fast and buy them often rather than stock up. If that’s not feasible, remember that optimal berry storage relies on a tricky balance of trapping humidity, but preventing drops of water from forming on the berries (all this even as berries release moisture as they age). So, if you need to extend the life of your berries beyond a few days or even a week, consider putting them in a container lined with a napkin (to absorb moisture) and with a lid left ajar (to both trap humidity, but also allow air to circulate). Freezing is also a great option–and in that case, rinse them and then freeze them right away!
Happy berry eating!
