I found my answer:http://www.foodsci.uoguelph.ca/dairyedu ... tml#cooked
But it does not say what temperature. And the taste should be as sweet. Just it should taste a bit like garlic, which is an unpleasant flavor.
Pasteurization is done at 75C. It should be noted that if it happens to you before 75C, then the flavor should happen at pasteurization. But as the link says, this flavor dissipates with time. So if you steam a milk at 70C, and put it in the fridge, you could resteam it the day after.
I read a paper claiming that foam is more stable for HTST milk at 85C while 65C for UHT (both whole). And from skim: 45C. The stability is the half-life. All the milks had around the same half-life at 85C. But note that your average temperature in your pitcher lower than the effective temperature at the output of the steaming wand. But it shows that like you said, temperature for the foam is still OK after 65C.
I will try to heat samples of milk heated at different temperature and cool them down at the same temperature, then do a blind test.