Last Christmas, for gifts I made herb-infused olive oils for a few people. I’m aware of the risk of botulism spores (which are found on plants) thriving in such an environment (trace amounts of water, no air) and that homemade herb-oils can be risky. To avoid that, I used three distinct methods:
For herbs, like rosemary, I dried them in a dehydrator for longer than normal. No water means no botulism.
For things like garlic and peppers that don’t dry very well, I only used products that were pickled. Pickled garlic. High acidity means no botulism.
I steeped the oil at a temp at or near 230F for a few minutes before bottling.
I used the oil, the people I gave the oil to used the oil, nobody got sick or died.
**
The Predicament:**
Flash forward to right now, a year later, and I have a few unopened bottles hiding in my closet. One of them is a rosemary garlic oil, and I’m planning on doing a rosemary turkey on T-Giving, so I figure this would be perfect to coat the bird.
But I’m hesitant, still.
The oil has had almost 12 months to sit, with the rosemary and garlic cloves in there. If there was a trace amount of botulism, in a year it could have turned into a colony.
But then, if I’m only putting it on the outside of the turkey, the heat from roasting would certainly kill any critters in there, right? I probably wouldn’t dip a baguette in it and chow down, but for cooking it should be fine, right?
There are no visible indicators for botulism, so there’s no way I can eyeball it or sniff it to check for funkiness.
Normally my instinct in such situations is to err on the side of safety, but lately I’ve been making a point about not being such a puss about things that are unlikely to hurt me.
Homemade herb oil sitting unopened (cork top with heat shrunken plastic seal) in your closet for a year. Do you consume it?
The heat of roasting will kill any botulism, but it will not neutralize any botulism toxin that may have been produced. If you wouldn’t eat it raw, don’t eat it cooked.
If the bacteria has been present and has been growing, it will have excreted botulinum toxin, which is a protein. Roasting heat won’t touch it.
I have a microbiology degree, and I generally think people are way too paranoid about food safety. I wouldn’t eat the oil. You’ve taken reasonable precautions, but nothing you’ve done will guarantee that it’s botulism-free, and botulism is nasty stuff.
My 9th-grade Biology teacher, from whom I learned all I know about Clostridium botulinum, left me in 41 years of abject terror of it, to the point that I argue against using its toxin to make one more attractive. (shudder)
Like Smeghead, I have a microbiology degree, and I worked as a food/industrial microbiologist for about 15 years (different to medical - no ability to tell what bug is causing your cold, but if your flour won’t hold a set, or you ate a dodgy fried rice, I’m your gal). As I haven’t worked in the field for many years, I would in general bow to Smeghead’s knowledge, as it is definately more current.
However, bacteria which produce toxins often produce heat stable toxins, and some produce heat labile toxins (can be cooked off). Some sneaky little bugs produce both (B. cereus, I’m looking at you). Back when I was doing micro, there were several variants of Clost. botulinum, which broadly related to the environment where the bug was sourced (bottom of a stagnant duck pond, vs dusty land v cannery cooling water). And there wasn’t just one type of botulinum toxin, there were about 7*. The botulinum toxins I am most familiar with are heat labile.
Quoted because I would say the exact same thing:
I age my salamis in an airing cupboard and I curry and eat meat that my husband thinks is off. I’d throw the oil out.
*Hedging in case they got renamed/reclassified since I worked in this field.
It’s not the garlic I wanted, but the rosemary. Imagine the potency of a bottle of olive oil stuffed with rosemary after a year. The allure of that was blinding me of my scientific and prudent sides.
I’ve got some 9 year old canned mushrooms, I’ll just use those instead. The tin has bulged out, I assume that’s bulging with flavor.