Can I Use Plastic Containers For Fermenting Food?

“I’ve just started fermenting vegetables at home, and I’ve been using glass jars so far. But I have a bunch of larger plastic containers I’d love to use because they’re bigger and lightweight. Are they safe for fermenting, or should I strictly stick to glass? I’ve read mixed things online, and I’m starting to feel confused. Any advice on what types of plastic or tips for safe fermenting in plastic would be great!

Thanks,
Andrew, Brisbane, Australia.”

Can I Use Plastic Containers for Fermenting Food?

Good question, Andrew! I totally get the confusion. The good news is you *can* ferment in plastic containers, but you just need to be a little picky about which type of plastic you choose. The safety of your food is the top concern (and probably why you’re getting mixed information), so let’s clear up when and how plastic can actually work for fermenting without putting your health—or your precious fermented goodies—at risk.

Here’s a quick dive into what you need to know about using plastic for fermenting, along with tips and real-life examples. This way, you can use those larger lightweight plastic containers with confidence—or decide to pass if they’re not the right fit for your fermenting adventures.

Why Some People Hesitate with Plastic

There’s a reason fermenting experts often caution against using plastic containers. Some types of plastic can leach chemicals into your food during the fermentation process. This is especially true when your food is in contact with the container for a long time (like it usually is with fermentation). Fermenting generates acids, and these acids can cause certain plastics to break down, releasing chemicals you really don’t want in your sauerkraut or pickled veggies.

The most common concern people have is Bisphenol A (BPA), a chemical compound in certain plastics linked to potential health risks. There’s also concern about other plastic contaminants like phthalates, which can leak into your brine when the wrong kind of plastic is used. Generally, when people avoid plastic, it’s because of these reasons.

Which Plastics Are Safe for Fermenting?

To avoid those nasty chemicals leeching into your ferments, you’ll need containers made from “food-grade” plastic. Not all plastics are created equal, and thankfully the ones that are food-safe (like certain numbers) can work just fine.

Look for “Free from BPA” Plastic

The first thing to check on any plastic container is whether it’s labeled as BPA-free or “food-grade.” BPA-free literally means it doesn’t have Bisphenol A, so you can worry less about chemical contamination. These plastics are tested to be non-toxic for food contact and tend to resist breaking down, even when you’re fermenting foods that get pretty acidic, like kimchi or kombucha.

Use Plastics Labeled with Safe Recycling Codes

Plastic containers come with those little numbers inside the triangle, and those numbers actually tell you quite a bit about how safe they are for fermenting:

• #2 (HDPE – High-Density Polyethylene): This is one of the safest plastics for food storage. HDPE plastics are resistant to acid and don’t easily break down. Think of the big white food tubs that restaurants use – often made from HDPE.
• #4 (LDPE – Low-Density Polyethylene): Also a good option and generally food-safe. These are the softer plastics often used in bags or food wraps.
• #5 (PP – Polypropylene): Another strong and food-safe material. This type of plastic is often found in yogurt tubs or other food containers specifically designed for multiple uses.

Steer clear of plastics with #3, #6, and #7. These can include harmful chemicals like BPA or phthalates, which aren’t what you want in close proximity to your delicious batches of pickles or fermented hot sauce.

Why pH Matters When Using Plastic

The pH of your ferment matters a lot when it comes to plastic safety. Food gets pretty acidic during fermentation, which is exactly what’s needed to create that fun sour flavor. But acidity is also why people are extra cautious about using plastic. Certain plastics break down faster in acidic environments, so you want a material that can handle those conditions without degrading.

Plastics labeled as food-safe or BPA-free are designed with food acids in mind, so they won’t dissolve or leach chemicals when the pH gets low. This is why Andrew’s situation—with having large plastic containers—could be totally fine as long as the plastics are the right type.

When Should You Avoid Plastic Altogether?

Okay, Andrew, I know you’ve got a stash of plastic containers calling your name, and that big volume they offer is definitely appealing—especially if you’re fermenting in large batches. But sometimes, even with everything looking good on the “food-safe” front, it might still be better to stick with glass or ceramic for fermenting.

Here’s why you might want to avoid plastic altogether:

• If the container has scratches or is worn down – Fermentation is a funky, active process. If your plastic container is old or has been dinged up, those cracks can harbor bacteria. Scratched plastic is less safe because it’s harder to clean well and prone to harboring unwanted, and potentially dangerous, microorganisms.
• If you’ve got any doubt about the type of plastic – Play it safe! Even though I’ve told you what to look for, if the container isn’t clearly labeled or doesn’t say it’s free of harmful chemicals, it’s probably not worth the risk—especially after you’ve already put all that effort into growing your food or buying fresh, organic produce for your ferments.

A Good Rule of Thumb with Plastic Fermenting

If you do decide to use plastic for fermenting, inspect your containers regularly. Look for any discoloration, cracks, or weakening. And keep in mind that food-safe plastic is usually better for short-term fermenting. If you’re planning on letting something ferment for several months—or even a year—maybe stick to glass or ceramic. For something like a quick 3-week sauerkraut or a 10-day pickle, Andrew, you’re likely in the clear with the right plastic containers.

What Should I Use for Covering Plastic Containers During Fermenting?

Since fermentation containers need a good airflow setup, figuring out what you cover your plastic container with is just as important. A loose lid or fermentation weight can work, but you want to avoid using any plastic wrap or airtight plastic lids. Ferments need air to breathe.

Here’s a trick I use: you could cover the top with a breathable fabric, like a clean dish towel, and secure it with a rubber band. I know it’s not fancy, but it gets the job done! Make sure airflow is happening, but nothing that can cause spoilage (think: fruit flies) can get in.

Other Alternatives to Plastic Containers

Andrew, if you’re on the fence about plastic, it’s good to know the other options you’ve got. Glass, as you’ve been using, is always a top contender. Actually, I love glass because you can *see* what’s happening in your ferment! Plus, it’s non-porous, so you’ll never worry about leaching chemicals or flavor. It’s a bit heavier (okay, a *lot* heavier than plastic), but it’s pretty much perfect for most home fermentation adventures.

Ceramic crocks are another fan-fave—they’re specifically designed for fermentation and are safe for those long-term projects that look like they’ll take a while—like fermented hot sauces or miso. If you can get your hands on a good crock, it might be worth adding to the collection.

Troubleshooting: Common Issues with Fermenting in Plastic

1) Cloudy Brine

If your brine gets cloudy, don’t panic! This happens with ferments no matter what container you’re using, plastic or otherwise. However, in plastic, you do want to ensure your container isn’t breaking down or leaching anything into the brine. If you used food-safe, BPA-free containers, cloudiness is probably just a normal part of fermentation.

2) Rancid Smell

If you open up your plastic container after a week or two, and something smells really off—like old socks kind of off—you might be dealing with contamination. This is especially true if your container had any nooks, crannies, or scratches before you started fermenting. While ferments always have strong odors (looking at you, kimchi), anything rancid is a sign to toss the batch and start fresh.

3) Mold Growth

Mold can pop up when you least expect it, regardless of your container type. In plastic, however, mold might indicate that the plastic container wasn’t cleaned thoroughly or had some residual material. In general, mold on the surface of a ferment (the “top few inches”) is fairly normal, just scrape it off and go about your fermenting business. But if the mold has taken over deeper layers, it’s safer to toss the batch.

Final Thoughts…

Andrew, thanks again for your question—it’s one that trips up a lot of at-home fermenters, especially when you’ve got so many types of containers lying around and don’t want to spend a ton of money replacing things that might actually be useful. The key takeaway here is that yes, you can use plastic for fermenting, as long as it’s BPA-free and food-grade. Paying attention to the number on the bottom of your container and monitoring for wear and tear will keep your ferments clean and safe. Whether you stick to plastic or try out some new options like glass or ceramic, have fun experimenting!