Written by adam on May 1, 2007
Heating Kills Botulism for Infused Oils
Filed Under: Tips
A year ago, I posted a quick recipe from Giada de Laurentiis entitled Rosemary infused olive oil. In it, I wondered why, exactly, we would choose to heat the oil. After careful thought, I concluded that it was probably to extract as much of the flavor from the rosemary as possible.
However, this may not be the case. A reader sent me some information that may shed some light on why we would heat oil to make infusions.
The answer is pretty serious, botulism
. If you use fresh herbs (in particular garlic) and cover them in oil, you risk breeding the bacteria that produces botulism. Botulism thrives in anaerobic conditions (no oxygen). It's a small risk to just throw a sprig of rosemary in olive oil and leave it out on your counter for a week...it'll probably be fine. But, there's a chance it wouldn't. That's why you see so many recipes that heat it to a certain temperature (to kill the bacteria), or to place it in the refrigerator and use within a week. It's another reason to NEVER use (in food) those decorative oil bottles with herbs in them at home stores!
So, heat the oil before infusing it if you want to keep it around more than a day or so. Else...if you want to use a rosemary infused oil for an evening meal...bruise up a CLEAN fresh rosemary sprig or two and cover in oil in a very clean glass container, put a lid on it and stick it in your fridge the night before. It'll have a subtle flavor. If you want more flavor...then do the cooking method. If you don't scorch the oil, it'll have no effect on the taste. There are recipes out there for doing oil infusions in a slow cooker where the risk of scorching is very very low.
So there you have it. I wonder how bad it is to use fresh garlic on my food. Or any other herb for that matter. I guess just basic sanitary procedures are key.
Sources: Henrietta's Herbal, Olive Oil Source, NPR
Responses to "Heating Kills Botulism for Infused Oils" ...
Do you think if I filled a canning jar with extra-virgin olive oil and whatever flavorings I want to use, then closed it, and boiled for a while to heat the oil and ingredients up over 180, would it then be safe to let that sit at room temperature for a while before using it?
Yes, I do believe that would work. I would suggest heating it hot and heating it fast. The longer oil is under heat, the faster is breaks down and turns rancid.