Chilli oil is a great condiment – and one of the few kitchen staples with a real botulism risk. The rule: dried chillies only, small batches, refrigerate and use quickly.
Why be careful
Oil seals ingredients off from air; if they contain water and are not acidified, conditions arise in which Clostridium botulinum can grow and produce toxin. Botulism cases from garlic in oil led the US to require commercial garlic-in-oil to contain an acidifier. The University of Idaho, Oregon State and Washington State University point out that safe acidification for home infused oils has only been tested for garlic and a few herbs – not for peppers – and that there is no tested method for canning flavoured oils.
Safer method
- Use dried chillies, never fresh, and no fresh garlic.
- Ratio from the PNW 664 research: 1 part flavouring to 10 parts oil; heat the oil with the chillies to about 60 °C (140 °F) for 5 minutes.
- Make small batches, store in the fridge and use quickly.
How long? Advice differs. The strictest, research-based guide PNW 664 gives 4 days in the fridge for oil with dried ingredients (or freeze it); Colorado State says 10 days; Penn State allows up to 3 months refrigerated for dried-herb oils. Clemson says to discard oil left at room temperature for more than 2 hours. We recommend the strictest limit.
Want a chilli condiment that keeps longer? Try a fermented hot sauce or dried chillies.
Safety: wear gloves when cutting hot chillies and do not touch your face. If you do not wear gloves, wash your hands thoroughly with soap before touching your eyes.
Sources
- University of Idaho, Oregon State, Washington State (PNW 664): Making oils safe to use
- Penn State Extension (2024): How to safely make infused oils
- Clemson HGIC 3471: Herb infused oils
- Colorado State University 9.340: Flavored vinegars and oils
- Nummer B. A. et al. (2011). Food Protection Trends. PDF