Hot, mild and sweet peppers all ferment the same way: cover them with a weighed salt brine, keep them under it, and let the lactic acid bacteria on the peppers sour them over one to two weeks. This page is the master method; for specific recipes, see fermented jalapeños, fermented banana peppers and, to blend the result, our fermented hot sauce.
The Brine
Use a 2–3% brine by weight: 20–30 g of non-iodized salt per litre of unchlorinated or boiled-and-cooled water. Weigh it, because a tablespoon of fine salt and a tablespoon of flaky kosher salt differ a lot. 3% (30 g per litre) is the forgiving default; 2% sours faster but softens sooner. Brine that’s much saltier slows fermentation without making it a shelf-stable product.
Timing by Pepper
- Thin-walled hot chillies (cayenne, bird’s eye, Fresno): often sour in 5–7 days; prick whole ones so the brine gets inside.
- Thick-walled peppers (jalapeño, serrano, poblano): usually 7–10 days, faster sliced.
- Mild and sweet peppers (banana, bell, mini sweet): their sugar ferments quickly; taste from day 4–5, as they soften sooner.
At 18–24°C, start tasting at about day 5. Warmer rooms are faster; cool ones slower.
When It’s Done, and Safety
Peppers, garlic and onion are low-acid foods; it’s the lactic acid made during fermentation that brings the jar below pH 4.6, the line food-safety rules use for acid foods (21 CFR 114). So refrigerate only when the peppers are clearly sour, and don’t treat them as shelf-stable or can them. Keep everything submerged: a flat white film is usually kahm yeast and can be removed, but fuzzy or coloured mould, a rotten smell or slimy peppers mean the batch should be thrown out (NCHFP). Wear gloves when cutting hot peppers – capsaicin burns skin and eyes.
Eaten raw, fermented peppers contain live lactic acid bacteria, which makes them a fermented food rather than a probiotic (Marco et al., 2021). Refrigerated and kept under their brine, they stay good for a few months, slowly softening and getting more sour. See the troubleshooting guide if a batch misbehaves, and NCHFP’s general fermenting guidance for the basics.
