Milk is practically alive...
Like Olembe, I worked for a large dairy. I wasn't a big fan of milk to begin with, I feel my stomach is telling me something ain't quite right when I drink it. I worked in the lab testing samples of every batch of cartons, bottles and polybottles that came off the line.

You'd do a rake of chemical tests on the ones about to be sent out. Any problems would be shown up by it having the wrong freeze point, fat content, etc. The offending batch could be removed.

But the biological tests? You'd stick a sample in a petri dish with some agar, and leave it in the fridge for three days. By now the milk had already gone out to supermarkets. After three days, a dodgy batch would have colonies of bacteria easily visible - no microscope. So those batches get recalled, having already been on sale. I saw this happen many times.

Particular lines were a problem, usually a glass bottle one. Apparently corner joints of pipes delivering the milk to the receptical get pretty mucky. Since we provided to most of the major supermarkets, I could identify which milk came from which line in the shop and avoid accordingly.

BTW - milk is cleaned by having a hydrogren-peroxide solution passed through it. It's called Oxonia and it's deadly stuff. Part of the chemical tests on the outgoing milk involved detecting it, and I only did so once. You get to shout "Oxonia on the line!" and all hell breaks loose until it's fixed. I makes me smile when I see adverts for this "twice-filtered milk", probably had it satured in deadly chemicals twice
(Cryptoprocta has abandoned the username of Voodoo Mary, Sat 29 Sep 2007, 11:27, Reply)