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[_creeks_]

Hello everyone,

I work as a lab technician in a goat cheese manufacturing facility, where we perform routine microbiological controls on both intermediate and finished products. We use 3M Petrifilm Coliform Count plates for in-house testing.

This week, we obtained a coliform count of approximately 1700 cfu/g on a finished, MAP-packed goat cheese product made from pasteurized milk. To rule out errors, I re-tested a counter sample the next day and got a similar result. Confident in our process, we sent a retained sample to an accredited external lab, which reported <10 cfu/g.

This contradiction have left me puzzled. All handling and incubation conditions were properly controlled, and the samples came from the same production lot.

I’d like to ask:

Has anyone else faced such discrepancies between Petrifilm and external lab results?

What factors could explain such a large difference in coliform counts?

How do you usually handle this kind of situation when it comes to internal quality records or non-conformities?

I'd say this happens quite often...
I’d really appreciate your insights or shared experiences.

Thanks!!