I think the main difference is fresh. When I was in high school I stayed with a dairy farmer who brought in a jug of milk from the tank for breakfast after milking the cows. After that I can't drink regular milk.
Pasteurization does affect taste though. Around me there are two different dairies, one does regular pasteurization and one does vat pasteurization and I can tell the difference. There is ultra pasteurization which is just gross. I've never put unpasteurized head to head against equally fresh pasteurized though, and given what I now know I'm not going to.
I love ultra pasteurization. I'm lactose intolerant so I have to drink "lactose free"[1] milk and in Canada such milk is often UHT pasteurized since it has to stay on the store shelf longer (lower inventory turnover). It's amazing that we can, non-chemically, disinfect a dairy product in such a way that it will stay good for months even without refrigeration.
In Mexico I suspect that almost all milk is ultra pasteurized since it's not refrigerated in stores and has wicked-long expiration dates. It's also some of the best-tasting milk I've had so I think that flavour has more to do with some of the other milk processes (like skimming) and the livelihood of the cows rather than with how it's pasteurized.
[1] In practice this is just milk with the lactase enzyme added at some point during production.
I have no doubt that milk that is 15 minutes old tastes great. My question is if that jug of milk was divided in two and one half was pasteurised, would people be able to tell the difference? You're saying yes, I'm saying I'd like to see blind tests of people tasting both.
IF you read close you will see that I didn't say yes. I said that I don't know and am not willing to be part of such a blind test. I will state clearly that all the unpasteurized milk I had was less than an hour old and tasted great, while all the pasteurized milk was unknown age but likely at least a day old and tasted worse. Is it fresh or pasteurization that makes a difference is not something I know.
Pasteurization does affect taste though. Around me there are two different dairies, one does regular pasteurization and one does vat pasteurization and I can tell the difference. There is ultra pasteurization which is just gross. I've never put unpasteurized head to head against equally fresh pasteurized though, and given what I now know I'm not going to.