Clostridium botulinum is a problem in herbal oils.
That is, if you want to eat your herbal oils. However, I've always thought that botulinum isn't a problem if the infused oil is used externally ...
So you'll find botulinum spores in soil, among other places. Clostridium botulinum is an anaerobic bacteria, which means that it needs water and no air in order to grow. The spores or bacteria aren't toxic, but as the bacteria live, they pee out their extremely toxic toxin. Which you can't detect by sight, smell, bubbles, color, or anything at all ... until you wake up a quadriplegic, or (if you're luckier than that), you wake up dead.
You have a few choices:
- If you crush your garlic (or your basil / parsley / dill / whatnot) in oil, let it sit in the fridge for a few hours, and use it, there's no problem: the bacteria needs time to grow and start peeing out toxin.
- If you use dried herbs (and/or dried garlic) in your oils, there's no problem: everything requires water to grow, including Clostridium botulinum.
- If you add enough salt (4 %?) to your oil, there's no problem, but then your oil will be salty: bacteria won't grow if things are salty enough. (This is what saves the various "feta in oil" products.)
- If you add enough vinegar to your oil, there's no problem, but then your oil will taste of vinegar: bacteria won't grow if things are acidic enough.
You can also try to get rid of the spores, bacteria, and toxin:
|If you wish to get rid of||heat things to||for|
|the spores||80-100 C||30+ minutes|
|the toxin||80-100 C||10+ minutes|
|the bacteria||80-100 C||10+ minutes|
(That's internal heat for the "heat things to" - use a meat thermometer, or whatever.)
You get heat from a waterbath setup, but you don't get enough heat from it: beeswax melts at 63 C, and my waterbath setup won't melt the beeswax I've added to the oil -- unless I raise the temp to bring the water to a rolling boil, and keep it there until the beeswax has melted. YMMV.
Live long and prosper: don't store your garlic-in-oil for more than a few days, if you made it with fresh garlic and haven't added enough salt and/or vinegar to it.