Kimchi Fermentation Time Calculator

The magic of fermentation is when the cabbage tastes like itself. It transitions from tasting like salty vegetable to tasting like what it is going to taste like. This isn’t instant. And staring at the jar while turning up the heat won’t help you hurry it along. The window between raw crunch and overcooked mush has a very small opening, and if you miss it, you’re starting over.

How do you know when? Before you put your fistful of leaves into a crock, this calculator will tell you. It takes all those pesky variables that usually confuse home fermenter and turns them into a calendar you can use.

How to Use the Fermentation Calculator

Bacteria don’t just pay attention to peak temperatures, either; they’re more concerned with averages. So if your kitchen average sixty-eight degrees in the morning, but jumps to seventy-five when the oven turns on, that’s an important factor for acid production. The tool above accounts for this because lactobacillus operates exponentially faster at warmth, and exponentially slower at coolness. This is why the output during the “room” stage shift dramatically with a mere five-degree difference. And contrary to expectations, it doesn’t happen in a straight line: Biological activity speeds up much more faster as it gets warmer. Regardless of the recipe you follow, a jar left next to a running dishwasher will sour twice as quickly than another kept in a shaded corner of the same room.

Salt is the other great equalizer. A final batch with two point four percent salt (though tedious to achieve) removes the guesswork regarding timing. Too little salt and the microbes will race ahead, too fast, often resulting in slimy texture before deeper flavors emerge. If you oversalt, they hesitate; you get pickled cabbage instead of the complex tang of true fermentation. Because the speed of microbes is directly controlled by their salt concentration, the calculator set its own timeline based off that balance.

It’s a bit of a tradeoff, of time, of texture, of safety. You can’t have max crunch and min wait time. So what does the tool do? It helps you choose which you value most for this particular batch.

It’s easy to overlook jar fill level until it’s too late. It makes sense to pack as much into a jar as possible, but then what happens when fermentation gases cause your brine to expand, pushing all contents right out onto your counter? Two inches of headspace gives the gas room to expand while still keeping solids floating where they belong, without any spills. This table on the page demonstrates the relationship between fill level and build up of pressure. You don’t want a jar filled to ninety percent to be tightly sealed because that spells trouble (popped lid, messy cleanup). Release that pressure by burping!

How frequently do you need to do this? That depends on how many gas your particular batch produces. For instance, bigger batches produce more gas, so the tool use weight to calculate how often you should of burp.

The fermentation pace varies from vegetable to vegetable due to cell structure: sliced cucumbers and cubed radishes will all be penetrated by the acids more quickly than the layered interior of napa cabbage shields the heart; the thick, stubborn root vegetable known as kkakdugi take longer to break down (thus retaining more crunch) while it ferments. The calculator accounts for texture, ensuring you don’t give your cukes the same treatment time as napa and wind up with a pile of mush. Choose a container that matches the contents.

After the stage of room temperature, however, your fridge take over as your aging chamber. The flavor will continue to develop (only slower), in the cool temperatures. That’s how the kimchi learns its personality. A fresh batch of kimchi is crisp and bright, while an older kimchi add the deep, savory sourness that makes fried rice and stews what they are. With this tool, you can estimate how long it should take until it’s matured enough in the fridge for you to try it out.

Don’t worry about opening it too soon. Usually smell is going to give you a better sense than time. If it has a clean, sharp odor, then go ahead and have some. Otherwise, something went wrong during the packing or salting phase, and it’ll smell like ammonia or rotten eggs (ew), rather than just being a jar that is simply sleeping. Let the calculator help you set your expectations at first, but trust your nose even more than the algorithm.

Don’t spend a lot of time looking at a jar thinking, “Is this done yet? Am I imagining things?