I am making chilli oil using light olive oil, crushed chilli, dried garlic, dried fennel seeds and parsley. I have been making this for years. I am concerned about this Botulinum business. Should I be concerned? And what can i do to avoid this?

Currently, I heat the olive oil before putting it into the mixture, jar it, and normally keep it in the cupboard for months, with no problems with taste.

Another thing I am wondering is, how does one measure the expiry date on homemade chilli oil? Can someone help?

3 Answers 3


Yes, you should be concerned. Botulism is obviously very rare, and most people never get exposed to dangerous amounts of it even if they follow unsafe practices. Nevertheless, simply heating/boiling a mason jar does not sterilize it, it only pasteurizes it, so this is an unsafe practice, especially when you add the element of room-temperature storage.

Low-acid food needs to be pressure-canned. Period. It's been discussed on this site and it's covered by the FDA. Here's a relevant snippet:

What is the Best Way to Prevent Botulism?

  • The control of foodborne botulism is based almost entirely on thermal destruction (heating) of the spores or inhibiting spore germination into bacteria and allowing cells to grow and produce toxins in foods. To prevent foodborne botulism:
  • Use approved heat processes for commercially and home-canned foods (i.e., pressure-can low-acid foods such as corn or green beans, meat, or poultry).
  • Discard all swollen, gassy, or spoiled canned foods. Double bag the cans or jars with plastic bags that are tightly closed. Then place the bags in a trash receptacle for non-recyclable trash outside the home. Keep it out of the reach of humans and pets.
  • Do not taste or eat foods from containers that are leaking, have bulges or are swollen, look damaged or cracked, or seem abnormal in appearance. Do not use products that spurt liquid or foam when the container is opened.
  • Boil home-processed, low-acid canned foods for 10 minutes prior to serving. For higher altitudes, add 1 minute for each 1,000 feet of elevation.
  • Refrigerate all leftovers and cooked foods within 2 hours after cooking (1 hour if the temperature is above 90 °F).
  • One of the most common causes of foodborne botulism is improperly home-canned food, especially low-acid foods such as vegetables and meats. Only a pressure cooker/canner allows water to reach 240 to 250 °F, a temperature that can kill the spores.

To summarize, in order to do this safely you need to do any or all of the following things (preferably all. in case you accidentally don't do one of the others correctly):

  1. Acidify or pressure-can the low-acid ingredients.
  2. Refrigerate the jars.
  3. Boil it again before consuming. (You don't need pressure-canning temperatures at this stage).

(Note that I am assuming "crushed chilli" is coming from fresh chillies and not dried ones. If you are using 100% dry ingredients then it is probably safe although not 100% risk-free - see the answer to dry garlic in oil --> botulism risk?)

P.S. Regarding expiration, the oil is either safe or it isn't. It's safe if it's been properly pressure canned, otherwise you should assume it isn't safe and boil it as per #3 above. If it's been properly pressure-canned, then it should be good until/unless the oil goes rancid, which is more of a function of storage conditions (temperature, light) than time, and which you'll definitely be able to taste and probably be able to smell.

  • I agree to your PS - Oil get rancid by light: Otherwise is a conservant. Apr 20, 2013 at 15:06

I have seen chili oil go rancid with and without heated oil. Neither way protects against the botulism toxin. Please note that this answer has been completely changed with now correct information (thanks to Aaronut and SAJ14SAJ):


Home canning methods don't kill the botulism spores (thanks Aaronut for pointing that out). You'd need to use pressure canning techniques (temperature of 121C for at least 3 minutes) to be be as safe as possible. Otherwise it's recommended that Oils infused with fresh garlic or herbs should be acidified and refrigerated.

The FDA's Bad Bug Book provides details as well as the following recommendation:

  • Because the botulism toxin is destroyed by high temperatures, home-canned foods are best boiled for 10 minutes before eating.

Finally the FDA has this fact sheet specifically covering information on how to deal with this bug.

  • Whatever purpose could the potato serve that a timer does not? That seems very spurious, and a waste of the potato. Also, as a low acid product, isn't pressure canning indicated?
    – SAJ14SAJ
    Apr 20, 2013 at 1:15
  • Sorry, on canning, I cannot go with the Nona principal. On almost anything else, yes :-)
    – SAJ14SAJ
    Apr 20, 2013 at 1:29
  • You boil your jar to sterilize it. I guess your jar is a glass jar. Potato serves to keep the temperature at boiling, without the jar explodes. You can also use a cloth that cover internally the pot and isolates the glass from contact with the bottom and sides of the pot. Olive oil can last for years if kept away from sudden changes in temperature and in the dark. In Greece and Sicily it is put in clay jars and buried up to his lids. Apr 20, 2013 at 8:44
  • @violadaprile: That's all well and good, but you need the temperature above the boiling point of water in order to kill C.botulinum spores. The jar does not "explode" if you use pressure-canning techniques, which is what is required for low-acid foods. Storing unsterilized oil containing low-acid food at room temperature essentially guarantees that any spores present will germinate. So this answer is wrong, and dangerous. Botulism is rare, and most of these infused oil preparations don't end up getting inoculated, but that doesn't make them safe.
    – Aaronut
    Apr 20, 2013 at 14:35
  • Glass jars explode if you boil them, with pressure canning too. The pressure is guaranteed by hot-filling, which brings out the hot vapors, and by the rapid closure, before the air returns. But if the reason for the potato is not that, then I assure you that in all my experience and my grandmothers and great-grandmothers had never heard. Apr 20, 2013 at 15:02

Cooking oils boil at temperatures hundreds of degrees higher than needed to kill botulism. Heat the oil and seasonings to the required temperature in the oven or on stove then make sure the container you will store the oil in is sterilized. After you pour the oil into the containers it is not different from any commercial oil you would buy that has been opened . As for expiration date, you'd have to research the specific oil you have and the expiration date it had when you bought it.

  • 1
    Cooking oils do not boil, they pyrolise, and that at temperatures much lower than needed to kill botulism spores.
    – rumtscho
    Dec 14, 2016 at 8:46
  • @rumtscho Not true: reports cite 120°C as the temperature to kill the spores, and most oils have smoke points over 160°C; some are over 250°C. Dec 14, 2016 at 11:54
  • @DanielGriscom good find! I remembered over 250 C for spore destruction for some reason, so that would have been well over most smoke points. Must have been misinformed.
    – rumtscho
    Dec 14, 2016 at 15:04
  • @rumtscho Can you provide some links verifying that oils don't boil?
    – Stu
    Dec 15, 2016 at 17:24
  • I don't have online sources for this, it is something I have read in books. You can find the information, although not so directly described, in Wikipedia, because cooking oils are mentioned in the pyrolisis article there: en.wikipedia.org/wiki/Pyrolysis
    – rumtscho
    Dec 15, 2016 at 17:38

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.