Can You Second Ferment Kombucha in Plastic?

Do you ferment your own kombucha at home? What kinds of containers have you used to ferment your kombucha? Glass? Plastic?

The use of plastic in kombucha fermenting is a bit of a debatable topic. That is, if you’re considering using it for second fermentation.

Here I’ll explain that although technically you can second ferment kombucha in plastic, it’s not recommended. The main reason being that the chemical reactions that occur with fermentation interact with the plastic, leaching harmful chemicals into your kombucha.

Let’s first discuss the basics of kombucha fermentation before getting into the details of second fermenting kombucha in plastic.

glass bottle of kombucha

Fermenting Kombucha

Kombucha has become a bit of a trend these days. For those of you who aren’t completely familiar with kombucha and how it’s made, let’s do a quick breakdown.

Kombucha is a fermented tea product that tastes sour but has hints of sweetness as well.

You can make kombucha at home relatively quickly with just a few ingredients. All you need are tea leaves, sugar, SCOBY (Symbiotic Culture of Bacteria and Yeast), water, and cooking and bottling instruments.

The fermentation process occurs twice for kombucha. In the first fermentation, you lightly cover the container so that the fermentation process can occur naturally. First fermentation takes at least a week and can last up to a month. The key with first fermentation is to taste test often.

The second fermentation is where the fun starts. This is when you get to flavor the kombucha and watch as the carbonation forms. For second fermentation, you want a container that closes tightly and one you can consume your beverage out of. There are a few different options for types of containers you can use, plastic being one of the easiest and cheapest to obtain. But can you actually use it?

Can You Ferment Kombucha in Plastic Containers?

Though you can ferment kombucha in plastic containers, I highly recommend not using a plastic container for the first fermentation. This is because of the chemical reactions in the fermentation and carbonation processes that occur.

If you use plastic or other non-food safe materials, you risk harmful chemicals in the plastic (BPA, phthalates, etc.) getting involved in these chemical reactions and leaching into your drink. Unlike plastic, glass, food-grade ceramic, or stainless steel containers are inert and won’t react with the kombucha’s chemical reactions.

Another issue for plastic containers is their propensity to scratch. Large plastic drums may seem ideal for your initial fermentation, but you may scratch the bucket when you’re mixing your ingredients. And if you don’t sanitize your bucket thoroughly after a scratch, bacteria can build up in the tiny crevices.

Though kombucha deals with “good” bacteria, build-up in your first fermentation vessel can cause side-effects, both for you and your kombucha. Excess or unwanted bacteria can cause the SCOBY to die and stop the fermentation process, and if ingested, the wrong balance of bacteria can cause stomach upset (and more severe problems are possible in some cases).

If you do plan on using plastic products when you’re making kombucha, just make sure you choose food-grade plastic and avoid scratching or otherwise damaging the vessel. Also be prepared for the strong smell of kombucha to stick to the plastic (this isn’t as much of an issue with glass containers).

Overall, I would definitely take into consideration the harmful effects of plastic during primary fermentation discussed here.

large glass jars for fermenting kombucha

Can You Second Ferment Kombucha in Plastic?

The second fermentation occurs after your kombucha has reached its desired acidity and taste. It’s when you can add flavors like fruit juice, root vegetables, or spices to amp up the flavor.

Second fermentation is also where you can much more safely use plastic bottles compared to first fermentation. That being said, I still prefer glass bottles to completely minimize any risk.

The main attribute you should look for in a second fermentation container is a tight-fitting lid. The second fermentation is when you’re creating carbonation, and without a tight lid, that carbonation will escape. Plastic and glass bottles alike are good for this.

Plastic can be used during the second fermentation for two main reasons—duration of fermentation and acidity. The second ferment only takes two to three days to lock in the carbonation and flavors.

The kombucha won’t be sitting in the plastic bottle for nearly as long as it would for first fermentation, so your kombucha won’t interact with the plastic very much. Just make sure you’re consuming the kombucha fairly quickly after it second ferments and try to not reuse the bottle again.

Acidity in your kombucha slowly decreases from the first to the second fermentation. During the first, acidity is relatively high and can eat away at plastics. Many people reuse their first fermentation container. And if you’re reusing a plastic container, repeated exposure to high acidity can break down the plastics, leaving harmful chemicals behind.

Once you have finished the first fermentation though, your kombucha’s acidity has decreased to safe levels, and you can transfer it to food-grade plastic for the second ferment. The second ferment occurs with much less acidity and shouldn’t degrade plastic with one-time use (one-time being the key word).

Tips and Plastic Alternatives

One of the most common alternatives to plastic in the second ferment is flip-top bottles. These bottles have a rubber stopper that corks itself into the neck of the bottle. The rubber stopper is attached to a swing-arm that allows you to open and close the bottle for easy consumption.

Flip-top bottles are great for kombucha fermentation because they’re glass are and made for use in a single setting. Glass bottles, as outlined above, are inert and scratch-resistant, so it can be washed and used multiple times after proper sanitization. Single-serve bottles are great for kombucha because they lock in the carbonation until someone wants a drink.

three flip top bottles made of glass filled with kombucha

Glass growlers are another alternative for plastic bottles. If you’re making a large batch of kombucha and you’re planning on sharing with friends, growlers that hold a half-gallon or more are perfect. Sanitized glass is ideal for new ferments, too.

Other than standard glass bottles, containers like stainless steel water bottles or mason jars work well for the second ferment. Stainless steel is relatively scratch-resistant, but you still need to be careful when you’re emptying the bottle. Mason jars also make great kombucha, but you need to make sure the cap fits tightly on the jar.

In Summary

Kombucha is an incredible beverage to make at home because it takes relatively little effort (but a lot of waiting)! Once you’ve gathered all the ingredients, all it takes to make kombucha is the proper container.

Now that you know that you can use plastic for your second ferment of kombucha if you don’t have a handy, preferred alternative, you’re all ready to start making your favorite beverage!