2 replies to this topic

[Csmith]

We have test and hold product and are setting up our corrective actions. Our customer requires that this product tests at <10 for coliform and it came back from the lab with results at 10. I am having them retest the same composite. Will this be enough for corrective action if the test comes back  < 10 or should I pull more product and test it.

 

If it comes back at the with the same results or more what would be the next step? Test multiple samples? It is on hold and has passed all other tested including pathogens. Thanks

[Charles.C]

Hi Csmith,

 

I assume you mean <10 cfu/g.

 

What is the product ? RTE ? (anything added after baking etc)

 

The likelihood of further samples giving a result <10 cfu/gram depends on the (true) mean coliform level / standard variation in the relevant lot (assuming there is a lot). And possibly the procedure used to determine coliform.

 

I would think that baking should pretty much eradicate coliform IMO unless some later mini-contamination.

Assuming the lab procedure was a plate count method, the "<" usually means no observed colonies on plate while one colony would give a 10cfu/g result.

 

Maybe lab is a typo (missed the "<") ?

 

I assume you know that "coliform" bacteria are normally regarded as unrelated to food safety.

[FurFarmandFork]

Grab yourself a copy of Microorganisms in Foods and use the investigation sampling plans in there for future incidents. At minimum I would determine what risk a positive coliform count indicates, then move on from there.

 

Your sampling plan depends on your goals, as Charles pointed out, what your retests will show you largely depends on the nature of the contamination, very rarely is contamination even throughout the lot, and working with a quantitative microbial limit at those low levels is not usually meaningful.

 

Typically, when suppliers state limits of <10 or none detective, they're looking for qualitative testing (presence/absence) and don't care about the number. And in a baked product it should pretty much be zero.

 

Retesting the original sample while also testing additional stratified samples throughout the lot and around the timestamp of the original can help you out. If all came back negative including the original, it could potentially have been sample contamination. If any of the retested samples (including the original) come up positive then you're back in a hard place where you can't say that there wasn't uneven contamination.

 

Those pesky "<" signs do occasionally go missing however, double check with the lab.