I know this is old, but I wanted to add my $0.02 since this is the first thing that comes up on Google when you search for pasteurizing fruit for beer. My wife is gluten intolerant so I've had to play with non-traditional ingredients quite a bit. I've probably now made two dozen beers with raspberries, blackberries, or both raspberries and blackberries.
1) If you want a really fruity flavor, you need to add the fruit in the secondary. I don't want a really fruity flavor. I'm looking for more of a note, not the whole song. The quantity of fruit is as important as when you add the fruit. So I add my fruit at the end of the boil since I'm going for a specific flavor.
2) I have only played with raspberries and blackberries, so I don't know how other fruits react, but what I like to do is:
a) Freeze fresh fruit,
b) When I start the beer I pull the fruit out of the freezer and set it with my other ingredients,
c) I don't boil more than than 2 gal for a 5gal batch (I just don't have the equipment), so when the boil is done, I turn the stove off, and add some water to bring the temp down to 200*,
d) I add the fruit. If I only add a pound it brings the wort down to about 180* (if it doesn't I add more water to get to 180*), which is on the high side but has been fine. If I add more than 1lb it brings the temp down more. I watch the temp to make sure I stay above 160*.
e) I keep the temp between 160-180* for 15min.
f) I then cool and pitch as normal.
I play with sorghum since I brew GF (sorghum makes cloudy beers). But, when I use just rice or do a non-GF brew, my beers come out crystal clear (no pectin haze).
For this past winter I made a (non-GF) milk stout with chocolate (powder and nibs) and 1lb of raspberries and 1lb of blackberries. It was fantastic.