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Butter, infused Oil and Botulism

henrikbe Jan 31, 2012 10:19 AM


I've been reading about infused oil and botulism (e.g. here: http://everything2.com/index.pl?node_...), and it seems that a general guideline to avoid botulism is to refrigerate the oil, and use it within one week.

Now, I just bought a pack of butter, and apart from salt, it contains no preservatives. Still, if refrigerated, it claims it will keep for about three months. So apparently, no risk of botulism there.

So I suppose it's the addition of the herbs that's the problem in infused oils. They are likely to contain spores, I guess, and also contain water which the bacteria need. However, butter also contains water, so that leaves just the spores as the only difference between butter and infused oil.

But then, since these spores are so hard to kill, I guess it's not very unlikely that some spores enter my pack of butter some way or another. For example, I might use a knife to cut some salad, and then use that same knife to take some butter. The risk is probably not high, but at least in some cases, this should transfer a few spores to the butter. And since the butter is comparable to infused oils in terms of botulism growing conditions, this might turn my butter into a deadly poison within a few weeks.

But I've never heard or read any warnings about botulism in plain butter. So my question is: Why is this not a problem? Are there other differences between butter and infused oils that I have overlooked?

  1. JMF Feb 1, 2012 03:11 PM

    Butter is made from pasteurized or cultured milk. So no problem. To safely infuse oil it should be heated, with the herbs in it, to 165 degrees. Held at that temperature for ten minutes. Then allowed to cool. The low temp. won't degrade the oil, but all bacteria are gone. When cool, pack the oil in jars or bottles. it will keep as long as it would normally, at room temp.

    7 Replies
    1. re: JMF
      acgold7 Feb 1, 2012 07:10 PM

      I'm pretty sure this will kill you. C. Botulinum needs to be processed in a pressure canner at 240F to be rendered inactive. At least that's what everything I've read says.

      Do you have reputable sources to the contrary?

      1. re: acgold7
        GH1618 Feb 1, 2012 07:22 PM

        Here's a concise discussion on the subject of botulism:


        1. re: GH1618
          acgold7 Feb 2, 2012 11:05 AM

          For those who don't feel like slogging through the entire report, here's an excerpt:

          "Process all home-canned meats and vegetables, with the possible exception of tomatoes, in a steam pressure canner at 240 degrees F for the time recommended in a current USDA research-based publication."

      2. re: JMF
        JMF Feb 2, 2012 01:42 PM

        I was thinking dried herbs, not fresh ones.
        But the temp of the oil has to 180F.

        1. re: JMF
          acgold7 Feb 2, 2012 01:44 PM

          So was I. I'm not sure it makes a difference, but I'm happy to be corrected if anyone can produce a source.

          Look, there's no problem if you are using an acidic environment, like vinegar, or a salty one, like a brine. But the absence of both as well as the absence of oxygen is just a prescription for disaster.

          1. re: acgold7
            JMF Feb 2, 2012 01:47 PM

            I did provide a source.

            1. re: JMF
              acgold7 Feb 2, 2012 05:56 PM

              Got it, thanks. You added the source after my post.

              Your info matches that in the other link above, which notes: "The toxin is a protein which can be inactivated by heating at 180 degrees F for 10 minutes."

              But it appears this refers to the toxin, not the spores.

      3. g
        GH1618 Jan 31, 2012 06:19 PM

        Here's a link to a brief article on the subject:


        1. a
          acgold7 Jan 31, 2012 05:44 PM

          Botulinum grows in the *absence* of air. As butter is left open to the air and the herbs in oil are completely separated from it, the growing conditions are not, in fact, comparable.

          1. mamachef Jan 31, 2012 10:32 AM

            Oh, they're very different. I wouldn't stress on the butter, but garlic frequently contains botulism spores and if you make it should be used within 3 days, not a week, and not for kids.

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