Milk going sour.

[Snowy Owl]

My OH has a thing about putting the milk back into the fridge the moment it has been used, this happens all year round, not just in the summer. However, I got to thinking, how long would it take for milk straight out of the fridge (say 4C) to reach the point where it would 'turn' in temperatures like we had earlier in the week?

[theprof]

Don't knock your OH because this is exactly the correct thing to do.

Psychotrophic organisms grow in milk at 7 degrees C, with some capable of reproducing at 5.5 to 6 degrees C. Given how close these temperatures are to normal fridge temperatures, you can imagine how long it would take for growth to begin to occur in milk that's been removed from the fridge during this heatwave.

[theprof]

Here's one I answered earlier:

http://www.theanswerbank.co.uk/Science/Questio n267573.html

[Snowy Owl]

Thanks for that, theprof. Most grateful for the link to your earlier answer too. Our milk is actually in glass bottles from a real milkman! OH will be delighted to know that he's been right all along. I have to admit surprise that some of those organisms can reproduce at relatively low temperatures, shows how important it is to check the temperature of the fridge.