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Canned Beer Micro Sampling Technique Questions

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  • Canned Beer Micro Sampling Technique Questions

    I've had a couple issues now with false positives in the lab for canned beer (using a mobile canner).

    On occasion one of multiple samples from a can will show growth (BBT samples are clean and the other canned samples are clean), so I'm thinking it is in my can sampling technique.

    My procedure is as follows-

    -Wipe down lab bench with 70% alcohol.
    -Working near an alcohol burner- no laminar flow hood, unfortunately.
    -Can tops are flamed using a propane torch for 5 seconds prior to opening- opened by hand wearing nitrile gloves sprayed with alcohol.
    -Samples taken using individually wrapped sterile pipettes and medium tubes inoculated and incubated.

    Since all of my tank samples are coming back clean, it doesn't seem to be a lab environmental issue contaminating the sampling procedures.

    My thought is that it is an issue with how I am opening and sampling the cans.

    Anybody have different means of sterilizing the top of the can prior to opening?

    Another more sterile means of opening it for sampling? Opening a can normally of course pushes the top of the can down into the beer which seems like a great way to contaminate a sample.

    See any other issues with my process?
    Jonathan Newman
    The Virginia Beer Company
    Williamsburg, VA

  • #2
    Your technique sounds very similar to the one I use. The only thing that I do differently is that I use a Kimwipe to wipe the lids with 70% isopropyl alcohol instead of flaming them. So far I haven't had any issues with false positives, so you could give that a try.

    Do you know which filler head(s) the contaminated samples came from, or are the cans taken from the line at random?

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    • #3
      some other tips

      I pretty much do the same thing, but here are a few more pointers.

      1. I spray the can top with iso and flame it.
      2. Wash your damn hands first!
      3. I work in proximity to an alcohol lamp.
      4. After opening up the can, I flame a piece of foil and rest it over the top when I'm not actively sampling.
      5. Shut the door. Make sure there isn't a lot of air movement around you that can bring stuff down.

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      • #4
        Looks like my process is pretty close to what you guys are doing.

        I'll definitely try alcohol+flame on the can tops instead of just the flame as I've been doing. Hopefully that helps.

        Thanks for the feedback.
        Jonathan Newman
        The Virginia Beer Company
        Williamsburg, VA

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        • #5
          Like Schue said, have you been able to look at a pattern in regards to filling heads sampled and contamination results?

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