You can still ferment in a summer heat wave. Here are some tips for fermenting in hot weather, including how to adjust your recipes for success!
Most alcoholic ferments are supposed to brew at around 60F (15C). Vegetables are meant to ferment at 63F (18C). Even warm ferments like kombucha or sourdough do best at 70F (21C). What are you supposed to do when it’s hot outside?
We live in the Pacific Northwest, on a small peninsula on an island, which means the cold pacific ocean is only about 3 blocks from my house to the North, South, and East. Even during the heat dome, our house didn’t get above 79F (26C). So hot weather fermenting wasn’t something I had to think about.
Then we went to visit our relatives in Australia…
My adventures in hot weather fermenting.
As part of our trip, we went to spend a week on Fraser Island. Not only is it a beautiful World Heritage Site, but it also doesn’t have access to most services, including a grocery store. With 8 people in our group, an average daily temperature of around 86F (30C), and only a small fridge, I knew we would need some fermented foods to help us last the week. There was no way fresh vegetables would last for more than a few days.
Our Australian relations were already fermentation-friendly sorts of people. They had a healthy kombucha culture, which meant their house had plenty of wild yeasts and bacteria. During our 3 week’s visit, we experimented with:
- Sourdough (gluten & gluten-free)
- Vegan kimchi & sweet and spicy pickles
- Friday Harbor miso dip, carrot chutney & tepache (from my cookbook)
- Cultured buttermilk (the simplest cultured dairy, perfect for travel)
It was hot and humid during our trip, and we didn’t have a way to keep our ferments cool. (Nor ourselves –heat rashes all around!) So I got a pretty good sense of what it is like to ferment in hot weather.
What happens to ferments when it’s hot outside.
- Hot weather favors yeast, so yeast-based ferments will go quite fast.
- Most mold also likes the heat. This is why tempeh ferments at 90F (32C).
The issue with a fast ferment is that it doesn’t allow time for bacteria to keep up with the yeast. Fast fermenting yeast can also produce bad-tasting fermentation by-products, like esters.
–> Fermenting in hot weather results in bad-flavored brews, mushy vegetables, and an increased risk of mold contamination.
There are four options for fermenting in hot weather
- Store your ferments in a cool location.
- Choose fast and furious ferments. (I couldn’t help myself. 😉 )
- Make warm-weather ferments.
- Do seasonal fermenting.
1. Tips for keeping your ferments cool on hot days
If you want to brew beer and wine or if you want to pack and preserve vegetables with fermentation, then you need to find somewhere cool (ish) to store your ferments. Between 64F to 68F (18C to 20 C) is ideal.
I don’t recommend using a makeshift option… keeping beer cool in a cooler filled with ice water for 6 weeks is a lot of work. Here are a few options that will let you ferment year-round.
- Turn an old fridge into a fermenting fridge or use a wine fridge to maintain the temperature.
- If you live in a house, build a cold room or cellar into your basement. Cool, dark locations are great for long-term food storage.
- Cold storage doesn’t just have to be built indoors. A pit in your backyard may be the coolest place around!
- Explore your home. You may have a cool corner of the house or closet. Usually, cool spots are on a lower floor on the north side of a building.
- Evaporation is a great way to keep things cool. Wrap a heavy wet towel around your ferments. You will need to wet the towel every 1 to 2 days, but it should help to keep things cool during a heatwave.
If it isn’t possible to keep your ferments cool, then you either need to stick with quick ferments, warm-weather ferments, or seasonal ferments.
2. Quick ferments
If you really want to make sauerkraut or pickles, then simply stick to short and quick fermentation times. Here’s how to pack fermented vegetables for the hot weather.
- Make sure to avoid contamination by using a jar that will allow CO2 to escape while preventing mold from getting in. I like Fido jars best. There’s no need to open or burb a high-quality Fido.
- For salt-brine ferments use at least 2.2% salt. Reducing the salt may lead to issues with mold.
- If you want to avoid salt, then use a culture to make sure everything ferments nicely. I like raw apple cider vinegar or honey.
Expect other ferments, like dairy, sourdough, and kombucha, to be extremely active in hot weather. Adjust your fermentation schedules accordingly. If it normally takes 24 hours to make kefir, reduce that time to 6-8 hours then store it in the refrigerator.
3. Warm weather ferments
Some types of ferments evolved in warm climates. These are perfect for a hot summer. There’s no need to use a yogurt maker when it’s hot outside! 🙂
Here are a few warm weather ferments:
4. Seasonal fermenting
Even in my cool-ish home, there is a seasonality to my fermenting. However, if you have larger variations in your seasons, then changing what you ferment based on the seasons makes sense.
–> I always brew beer when it’s cold outside. That way I don’t mind warming my house while the brew pot bubbles for 60+ minutes. It also makes it easier to cool down the beer before pitching the yeast.
–> Pack your over-winter ferments in the fall, when cooler overnight temperatures will help with cool storage.
–> Summer is perfect for fermented sodas when the heat helps them carbonate.
I hope this helps you figure out the best way for you to manage hot weather fermenting. If you have any other tips and tricks, please share them in the comments section!