I don't sterilize or pasteurize my fruit, personally. What I do is hand-wash and inspect every piece and make sure there aren't any bits that are rotting or show other signs of potential infection. Then I put it in the mesh bag, close the bag securely, and put the bag in a sanitized (closed) tupperware container and freeze it. That breaks open the inner cell walls, allowing you to extract more color and flavor from the fruit. For stuff like blueberries or blackberries, what I do then is bang it around a little bit to break open the outer walls...not a lot, just enough to crack the skin a bit. Then when I rack to secondary, I just stick that mesh bag in the bottom of the bucket and rack on top.
Some years ago I did some experiments with doing purees and pasteurizing and whatnot, and I found I preferred the flavor from using the above method. The pasteurized ones had a sort of "cooked" flavor going on. Not necessarily bad, but certainly there are some reactions that take place in fruit which changes the flavor substantially when you pasteurize it. I guess it's like the difference between eating a blueberry pie vs eating a fresh blueberry. They both taste good, and in many ways they are similar, but you can easily tell the difference between the two.
Also if you check around here and elsewhere on the internet, you will see people claiming that freezing the fruit sanitizes it by killing the bacteria, etc. This is completely untrue. All freezing does (apart from rupturing the cell walls in the fruit) is slow down growth while it's in the freezer. You want to have clean, fresh, undamaged fruit to start with.