Fermented Cherry Tomatoes

A simple, reliable shortcut is 2 tablespoons of salt per liter (about 4 cups) of water, this gets you close enough to a 3% brine for safe, successful home fermentation with most fine, kosher, or coarse sea salts. (The one exception is Diamond Crystal kosher salt, which is lighter per tablespoon than other brands, if that’s what you’re using, add slightly more to compensate.)

If you want to be precise, this recipe uses roughly a 3% brine by weight (salt weight ÷ total brine weight). To scale it up, scale down, or use a different container size, weigh your water and multiply by 0.03 to get the exact amount of salt needed. This is more reliable than measuring by tablespoon alone, since salt density does vary between fine, kosher, and coarse varieties.

Cloudy or milky brine is a normal sign that fermentation is actively happening. It’s caused by the lactic acid bacteria multiplying. It’s not a sign of spoilage.
The one distinction worth knowing: cloudiness throughout the liquid itself is normal fermentation activity. A distinct, separate white film sitting on the surface is a different thing entirely. That’s kahm yeast (see below), not cloudy brine.

There’s no single right answer here. Fermentation time is entirely down to personal taste. Most people ferment their cherry tomatoes for 4-6 days, but you can go longer if you want a deeper, more sour, more complex flavor. I currently have a jar at 10 days that I haven’t tried yet, but I suspect it’ll be incredible as a base for homemade BBQ sauce.
The practical signs to look for: the brine turns cloudy, small bubbles rise when you tap the jar, and the tomatoes taste tangy and slightly fizzy rather than just salty. Those are signs fermentation is active but they’re not a deadline, just an indicator you’re in the zone where you need to start tasting.
If you’re new to fermenting, start on the shorter end and taste a tomato daily from day 4 onward. The moment they taste good to you, move the jar to the fridge to slow things down. If you want more tang next time, just let the next batch go a day or two longer. There’s genuinely no wrong answer. Just experiment until you land on your own perfect flavor profile.

If you notice a thin white film on the surface of your ferment, it’s most likely a wild yeast, called kahm, that’s harmless to eat but gives the ferment an unpleasant, bitter flavor if left alone or mixed in.
Some fermenters scrape it off and continue fermenting underneath. I don’t recommend that here: kahm yeast can affect the flavor of the whole batch even after scraping, and it also makes it harder to keep an eye out for actual mold underneath. If you see it, it’s safest to discard the batch and start fresh rather than risk an off-tasting or unsafe result.

Kahm yeast vs. mold and how to tell the difference: Kahm yeast is thin, white or cream-colored, sometimes with a slightly wrinkled or lacy (like ramen noodles) texture, and it stays on the surface. Mold is fuzzy, raised, and often shows blue, green, black, or pink spots. If you see anything fuzzy or colored rather than a flat white film, that’s mold. Discard the entire batch immediately; don’t scrape and taste to check.

Store your fermented cherry tomatoes in the refrigerator for up to 6 months. Once they’re chilled, fermentation slows dramatically, helping preserve their tangy flavor and firm texture.
Keep in mind that refrigeration doesn’t stop fermentation completely, it only slows it down. The beneficial bacteria remain alive, so the tomatoes will continue to produce small amounts of carbon dioxide over time. For that reason, always store fermented tomatoes in the fridge or another consistently cold location rather than at room temperature. Leaving them on the counter after fermentation can cause pressure to build inside the jar, increasing the risk of leaks or even a messy “tomato explosion.”
As long as the tomatoes stay submerged in the brine and develop a pleasantly tangy aroma, they’re generally good to enjoy throughout their refrigerated storage life.