Kimchi is Korea’s national dish — vegetables salted, coated in a spicy paste, and left to ferment until they turn sour, funky, and alive with probiotics. Almost everything people wonder about it, from the smell to the gluten question, traces back to that one process: lacto-fermentation.
What kimchi actually is
Kimchi is most often napa cabbage and Korean radish, salted and then coated in a paste of chilli (gochugaru), garlic, ginger, and fish sauce. Like sauerkraut, it’s a lacto-fermented food: naturally present lactic-acid bacteria convert the vegetables’ sugars into lactic acid. That acid is what gives kimchi its signature sour tang, preserves it for months, and produces the live probiotics it’s famous for.
There are hundreds of regional and seasonal varieties, but the science behind all of them is the same, and it is shared with sauerkraut: see sauerkraut vs kimchi for how the two compare. It all starts with salt. Cabbage is usually brined at around 2–3% before the paste goes on. Get the ratio right with the salt brine calculator or the fermentation brine calculator so the batch stays crisp and safely sour.
Why kimchi smells the way it does
The smell is the fermentation working. As lactic-acid bacteria consume the cabbage’s sugars they release sour and funky aromatic compounds; the garlic, ginger, and fish sauce add their own sulphurous, savoury notes on top. The result is sour, pungent, and a little funky — sharper the longer and warmer the kimchi ferments. A strong smell is normal and healthy. Here’s how to read what your nose is telling you:
Keeping the vegetables pressed under the brine and the jar cold in the fridge holds the smell in the pleasant-sour range.
Is kimchi gluten-free?
Traditional kimchi is naturally gluten-free. The core ingredients — cabbage, radish, salt, gochugaru, garlic, ginger, and spring onion — contain no gluten. The risk sits entirely in the seasonings:
If you’re coeliac or gluten-sensitive, the safest route is homemade kimchi with certified gluten-free fish sauce and a rice-flour paste, or a commercial brand explicitly labelled gluten-free.
Related calculator
Fermentation Brine Calculator
Calculate salt using vegetables plus water, water only, or dry vegetable weight. Match the percentage and basis in your tested recipe.
How many probiotics are in kimchi?
Raw, unpasteurised kimchi is one of the richest food sources of probiotics. As it ferments, populations of Lactobacillus and related lactic-acid bacteria bloom, with Leuconostoc species early on giving way to Lactobacillus as it matures.
Two things quietly kill those probiotics. Heat: cooking kimchi above roughly 46°C / 115°F destroys the live cultures — it still tastes great and keeps its fibre, but the probiotic benefit is gone. Pasteurisation: shelf-stable kimchi sold outside the fridge has usually been heat-treated, so look for chilled, “raw,” or “unpasteurised” on the label if live bacteria are what you’re after.
Free Fermentation Salt Reference Card (printable PDF)
A printable PDF companion for the brine & pickling calculators and guides.
Quick kimchi facts
Make your own kimchi
Kimchi is one of the most rewarding ferments to make at home, and it lives or dies on the salt ratio. Brine the cabbage right, pack it under the paste, and let time do the rest. Loosen the lid daily during the first active week, or fit an airlock — see our guide on burping fermentation jars for the full schedule.
