6 replies to this topic

[sean_as]

Hi all

 

Can someone please in layman terms just explain why it's wrong to re-pasteurize milk say with 2 days only remaining of its intended shelf life and then giving it again its original shelf-life post pasteurizing. Yes, the heat treatment will give you acceptable micro counts, but what of the other factors. Trying to justify this to someone.

 

Thanks all in advance.

[Tony-C]

Hi Sean,

 

First of all, would it be regarded as ‘fresh’ pasteurised milk?

 

Pasteurisation tends to provide a selection process for bacteria and enzymes that survive the pasteurisation process so the shelf life of the re-pasteurised milk is not likely to be the same, you would need to conduct shelf life trials.

 

Also, I have previously come across requirements for fresh milk to pass a peroxidase test which is unlikely in re-pasteurised milk but this may not be applicable in your case.

 

Kind regards,

 

Tony

[GMO]

Alkaline phosphatase can partially reactivate after treatment and the test is to show its absence so that should not be an issue per se but as you know the issue you will have is pasteurisation is a gentle process, it doesn't kill all bacteria including those for spoilage.  So you will (in my opinion) have spoilage issues.  If you use for another purpose, e.g. cheese making you will have a different natural microflora going into your vats.

 

I've never worked in milk drying, not sure if that is an option on slightly aged, already pasteurised milk?

[sean_as]

Hi Sean,

 

First of all, would it be regarded as ‘fresh’ pasteurised milk?

 

Pasteurisation tends to provide a selection process for bacteria and enzymes that survive the pasteurisation process so the shelf life of the re-pasteurised milk is not likely to be the same, you would need to conduct shelf life trials.

 

Also, I have previously come across requirements for fresh milk to pass a peroxidase test which is unlikely in re-pasteurised milk but this may not be applicable in your case.

 

Kind regards,

 

Tony

 

 

Hi Tony, thank you very much for that explanation

 

Yes, this is for fresh milk which would have been pasteurized already but someone doesn't want to waste excess milk which now has 2 days left, so they want to repausterize and apply the normal shelf life for "fresh milk".

[sean_as]

Alkaline phosphatase can partially reactivate after treatment and the test is to show its absence so that should not be an issue per se but as you know the issue you will have is pasteurisation is a gentle process, it doesn't kill all bacteria including those for spoilage.  So you will (in my opinion) have spoilage issues.  If you use for another purpose, e.g. cheese making you will have a different natural microflora going into your vats.

 

I've never worked in milk drying, not sure if that is an option on slightly aged, already pasteurised milk?

 

 

 

Hi thanks for your response,

 

actually, this is for fresh milk that is almost at the end of its shelf life. It would have been pasteurized already but someone doesn't want to waste excess milk which now has 2 days remaining, so they want to repausterize and apply the normal shelf life for "fresh milk" which I don't agree with.

[GMO]

Yep, realise this was for fresh milk but wandered whether drying it could be an option if you sold it onto a company who does milk drying.

 

I agree, repasteurising and using "as fresh" is not something I can square with my gut as being acceptable.

[zakimasood]

Re-pasteurising milk near the end of its shelf life isn’t just about killing microbes—it’s also about quality and safety standards. While heat treatment can reset microbial counts, the milk’s proteins, enzymes, and flavour compounds have already begun to degrade over time, which means the taste, texture, and nutritional profile will still be compromised. Regulations also typically prohibit “resetting” the clock because pasteurisation doesn’t remove heat-stable toxins that some bacteria may have already produced, and relabeling could mislead consumers. In short, it’s not just about the bugs—it’s about product integrity, safety, and honest labelling.