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Fat goes moldy?

I was given a George Foreman grill a while back and I have to say it's awesome. I thought these were a gimmick but it works very well. I do one burger at a time for 5 minutes and they come out quite nice. I don't have to flip them and all the grease drains into the little catcher.

I cut off any fat and dump it, a long with the grease into a container.

At first I was using a big cup from Wendy's to dump the grease in. I noticed when it was halfway full and I lifted it up there was some mold on the bottom. It looked like white stringy cobwebs with black dots.

I thought fat did not go moldy? I thought only after long periods of non refrigeration it would go rancid?

I chucked out the cup and started using a plastic container and covered it. Not even a quarter full and this mold is back again growing near the roof of the container.

So should I be putting it in the fridge? I know bacon fat doesn't go moldy being left out...

I am not saving this fat for anything, I just need to store it before I can toss it. You can't dump it down the drain.


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  1. Maybe it is just me, I thought I remember seeing fat goes moldy before. I think render fat does not go molding, but unaltered trimmed fat can go mold at room temperature. It will be interesting to see others' replies.

    1. Unless you strained it through a fine mesh it probably had some solids in it and even if they are tiny, they will start to grow mold.

      1. Pure fat doesn't generally go moldy - it can go rancid though.

        But that's pure fat. If you aren't straining it very carefully, you could still have some non fat stuff in there, and that can go moldy.

        When you say 'cut off any fat' are you cutting off chunks of fat, cooked or non? Because generally the long lasting fats have been rendered first. Pure fat, before rendering, still has moisture and other solids in it (you can really see this while making lard, or ghee).

        1. Bacon drippings don't get moldy because they contain a lot of salt. Unsalted butter grows mold (and begins to taste like bleu cheese). Refrigerated and frozen fats become rancid.
          Since you do not want to reuse the burger drippings, it doesn't matter that they are moldy. If you don't want the container taking up refrigerator space, leave it out, covered, until you throw it in the trash.

          1 Reply
          1. re: greygarious

            If you clarify/render the fat, you get a long term stable product too, even without salt.

            Ghee (butter with the milk solids and moisture and salt removed) will keep for at least a year at room temperature, even in a tropical climate. Lard, made from pork fat with the moisture and solids cooked out, keeps for ages as well.

          2. It's not just fat that drains off; it's meat juices, too.

            1 Reply
            1. re: Violatp

              You are right. The GF grill unfortunately pushes out a lot of the meat juices, and they will spoil at room temp very quickly. If you are throwing it out, then I don't see a problem. If you want to use this fat for another purpose, then you need to refrigerate or freeze it.

            2. I keep some small paper cups around and dump grease I don't want to keep in those. After it's cooled a bit, I put it in the refrigerator to solidify. Then on trash day, I throw it in the garbage can before I take it out. No drain, no sitting around to get moldy.

              1. Thanks for the responses.

                I kind of forgot how much salt is in bacon so that makes total sense.

                The mold sure appeared fast, probably due to the heat. Like I said the container isn't even a quarter full.

                I don't mind leaving the stuff out as long as this mold isn't going to cause any health problems?

                1 Reply
                1. re: noodlez

                  Mold in your apartment can cause or exacerbate health problems, such as allergies, asthma, etc.
                  You mention that you trim the fat & put that into the container. I think that is quite possibly the culprit, especially if it is still raw when trimmed.
                  Keep the container in the fridge.