Fermented Mexican hot sauces — chillies lacto-fermented in salt water for 5–14 days before blending — represent a different flavour category from fresh or cooked salsas. The lactic acid fermentation (identical in mechanism to kimchi, sauerkraut, and other lacto-fermented vegetables) transforms the chilli's raw sharpness into a rounder, more complex, slightly sour depth. The fermented salsa's flavour improves and mellows over weeks of refrigerated storage.
- **Brine:** 2–3% salt solution by weight (20–30g salt per litre of water) — sufficient to suppress pathogenic bacteria while allowing Lactobacillus to flourish. - **Submersion:** Chillies must be fully submerged in brine throughout fermentation — any exposed chilli oxidises and can grow mould. - **Temperature:** Room temperature (20–25°C) — 5–14 days depending on ambient temperature and desired sourness. - **Blending:** After fermentation, the chillies are blended smooth with some of the brine — the brine is now a complex, slightly acidic liquid carrying the fermentation's flavour compounds.
Mexico: The Cookbook