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Problems with HLP tube interpretation

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  • Problems with HLP tube interpretation

    Is anyone else testing for beer spoilage with HLP tubes? I inoculate a 1 mL sample from the original wort, FVs, and BBTs. My problem is with the interpretation. It seems like there is small particulates in many of the tubes. Some look almost like a hair, others are more circular. This is even for some uninoculated tubes. I haven't seen anything that jumped out to me as being a clear positive result, but i've questioned some. How large are the colonies generally? I also tried to extract a particle from one of the tubes to gram stain it, however this was also difficult. I do not want to record false negative or positives.

    Any info on how to better interpret HLP tubes would be great.



    Thanks!

  • #2
    Ziggy, when you inoculate your tubes you should always use a control sample and inoculate it FIRST, so as to determine that the medium was not too hot for any bugs you're trying to culture and that the medium itself was capable of sustaining growth. Ideally you would use a culture with a known concentration of lactobacillus/pediococcus so that you can check whether the medium grows as many colonies as it should, but you can also just rinse a swab from your brewery floor drains. The control sample is good practice to ensure you aren't getting any false negatives, but it also gives you nice colonies to compare with your unknown samples.

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