Refrigerating produce in jars looks great, but it can breed bacteria

You’ve probably seen them: Images of clear glass canning jars filled with multicolored berries that look like little jewels. Asparagus stalks, plunked into a glass-turned-vase that doubles as a charming centerpiece.

Social media is awash with food-in-jars storage hacks that are a joy to ogle - but do they translate to real-life solutions? I asked produce and food safety researchers and experimented in my own kitchen to learn which of these storage tricks are worth it and which are recipes for things you really don’t want to eat.

Spoiler alert: While water soaks and vase treatments can perk up produce, experts said to beware of water submersion hacks promising weeks of shelf life - that invites microbial growth. Be careful with tightly sealed jars, they warned, which can suffocate living, breathing fresh fruits and vegetables. And remember that every type of produce has different needs and quirks, and every piece of produce has a unique history that could be the difference between quickly going fuzzy or staying pristine for a month. A hack that works this week could easily turn to mush next week.

The best thing you can do to extend the life of most fresh fruits and vegetables is to get them into the fridge as fast as possible, said Elizabeth Mitcham, emeritus director of the Postharvest Technology Center at the University of California, Davis.

“If you go to the farmers market and you buy produce, and then you wander around for a few hours, and then you finally get home and then put them in the fridge, you’ve already lost way more of the life of that product” than you’d gain from any special storage tricks, she said, especially on a warm day.

After keeping produce cool, there’s a delicate dance between storing it in ways that enable it to breathe, but retain moisture, among other factors (including that some whole fruits and vegetables don’t do well in the fridge). The crisper drawer is designed to help with this, but it’s a tough puzzle, which explains why we’re so hungry for hacks.

So here’s what to know about some popular produce storage tricks:

Celery and carrot sticks

The hack: Store celery and carrot sticks in a water-filled jar.

The takeaway: Use this trick to keep veggie sticks attractive and crunchy, but not to stretch shelf life.

In the short term, water submersion keeps celery and carrots crisp by preventing dry air from sucking moisture from their cells. It also prevents dried-out, white patches on cut or peeled carrots. Ben Chapman, director of a food safety research program at North Carolina State University, said a couple days or a week could be fine, but once weeks go by the water could help a small amount of bacterial contamination go from, say, a tiny corner of one celery stick to growing all over the sticks.

Chapman, who analyzed this scenario on “Risky or Not,” a podcast he co-hosts, said his top concern was listeria monocytogenes, a type of human pathogen with the unusual ability to grow in the fridge. In small amounts, it rarely sickens healthy adults, but it becomes more problematic, especially for immunocompromised or pregnant people, once it’s had time to proliferate. If your fridge rises above the recommended 41-degree Fahrenheit maximum, he said, listeria grows faster. Other types of harmful bacteria, as well as bacteria that simply spoil your food, also grow more easily in warmer fridges. After weeks in a too-warm fridge, you could have quite the petri dish, or, jar, of veggie sticks.

One plot twist, noted Don Schaffner, a Rutgers University food microbiologist and Chapman’s podcast co-host: While carrots aren’t immune to microbial growth, there’s evidence they have an unusual ability to inhibit listeria growth. He worries more about celery stored underwater.

Avocados

The hack: Submerge ripe, skin-on avocados in a jug of water and stash in the fridge to extend their life.

The takeaway: Do not submerge avocados in water. Instead, put them in the fridge once they’re ripe to keep them at their peak for a few more days.

Avocados need to ripen at room temperature, but once ripened, the fridge’s chill keeps them at their peak longer. If you halve the avocados first, water will slow oxidation, so they’ll appear good for longer.

But don’t do this. Over time the water can facilitate dangerous bacterial growth, even if the avocado looks great.

U.S. Food and Drug Administration sampling has found listeria on avocado peels, and while you should always wash your produce, a good cleaning can’t remove all bacteria. Additionally, an agency spokesperson told me, when FDA scientists stored whole avocados in refrigerated tanks for 15 days, they found listeria moved from the peel into the green flesh.

Asparagus

The hack: Store asparagus like flowers, in a “vase” in the fridge.

The takeaway: Trim the bottoms of asparagus stalks and stand them upright in a glass with water to keep them firm for a few days. Don’t leave them in water for an extended period of time.

This mirrors an industry practice of packing asparagus upright, with a wet pad at the bottom, said Mark Ritenour, a postharvest biologist at the University of Florida. The moisture fuels their thirsty, growing tissue and prevents shriveling.

If you create an “asparagus vase” at home, Ritenour suggests using a minimal amount of water for only a few days, citing, you guessed it, concerns about microbes flourishing in the water. He also advises cutting off the wet ends before prepping them.

So, I tried this. I split a bunch of asparagus in half, putting one handful in a glass with some water (which looked delightful in my fridge) and the other in a cotton bag in my crisper drawer. After several days, both bunches looked the same, maybe the vase stalks were a little firmer. Both sets roasted up nicely, so for me, for that bunch, it was not worth the time. Ritenour said it’s possible my set up kept just enough moisture in, and noted that my experience speaks to the endless variability with produce.

Berries

The hack: Put berries in a sealed glass jar and stash it in the fridge.

The takeaway: Do not store fresh berries in a sealed jar to extend their life. Instead, leave them in the clamshell container and put them in the crisper drawer of your fridge; or place them in a storage container lined with paper towels and leave the lid ajar. This will preserve some moisture while also allowing gas exchange. (For extended storage: Wash, dry and freeze them.)

A sealed jar traps humidity, keeping berries plump. But many factors, including how often you open the jar, will impact how they fare.

Even harvested produce takes in oxygen and releases carbon dioxide, just like we do. (This is separate from the plant kingdom’s more famous trick, photosynthesis, which, among other things, takes in carbon dioxide and gives off oxygen.) Different types of produce respire at different rates - respiration rate is a huge factor in determining shelf life - and delicate berries respire fast. Left in a sealed jar for too long, they’ll deplete oxygen and switch to anaerobic respiration, which churns out off flavors and eventually makes the berries fall apart, scientists explained to me.

I tried this method myself, leaving jars of berries tightly sealed while I was away for more than a week. When I came home, the jars’ inner walls dripped with condensation. The strawberries smelled of chemicals, and I had no interest in eating them. They were, however, more plump than the berries I left in the clamshell and showed no visible mold, so there’s that.

Another concern: As fresh produce’s respiration depletes oxygen in a sealed jar, it could create an environment that’s ideal for certain bacteria. In this case, berries’ acidity could mitigate pathogen growth, said Schaffner, the Rutgers food microbiologist, but not enough to dispel food safety concerns.

“Generally I think it’s a bad idea to store foods for extended periods of time, especially under anaerobic conditions,” he wrote in an email.

If you’re wondering how to square all this with the sealed bags and tubs of produce sold at grocery stores, Eva Almenar, a professor at the Michigan State University School of Packaging who specializes in produce packaging, noted that those are made with plastics that allow gas exchange.

But forget respiration for a moment. The risks of pouring delicate berries into a jar was enough to give Ritenour pause. “Whenever you’re touching the berries or moving the berries, you’re giving an opportunity for damage and the introduction or movement of potential decay organisms,” he said.

Ultimately, Ritenour said, don’t expect your produce to last forever. As long as you’re following best practices, if putting your fruits and veggies in a clear, pretty container makes them more enticing and gets them on your plate faster, maybe that’s the “hack” you need.