Can you vacuum lock fruit and hold in a freezer for X amount of time then just place the bag in a pot of 170* water for 5-10min. for pasteurization. I don’t see how this would be any different than the pasteurizing we do by just running bottles or cans through a 170* pasteurizer.
Simple answer to me is “I don’t see any reason that would not work”. Freezing may benefit you by bursting the skin on the fruit you use. Also remember if adding to secondary and most of us do when using fruit the finished beer will have enough alcohol contact to help prevent infection.
I’m not big on fruit beers so hopefully someone that brews them a lot can give some practical experience.
I use fruit a lot, but have never pasteurized it. Using unpasteurized fruit has let to infections, but never anything that ruins the beer. Using cooked fruit however would (in my opinion) ruin the beer.
Pasteurizing is an exacting process. You need to bring what you are pasteurizing to a temperature that is hot enough to kill any lurking microbes, but not hot enough (or not held at high temperature long enough) to cook the item. The ideal way to do this is the quickly heat and then cool a thin layer of the item. Frozen bags of fruit probably wouldn’t work well for that, unless you smashed them flat before you froze them. In that case, keep them hot just long enough to bring the pulp at the center to 170, then quickly cool them.
Good luck, and if you try this, report back how it worked for you.