I would wait till fermentation slows way way down. You could even transfer to a secondary if you wanted to free up a primary fermenter (I say this because I have glass carboys that I never use and I only have 6 or so buckets) I might freeze them first and maybe chop them a bit. There is some question about adding pits to the beer but I am skeptical about the risks
Yes. Like Mort said, I would wait until primary fermentation is complete. You are less at risk of contamination at this point. Some people will pasteurize the fruit, but I just freeze and thaw. This will kill off bacteria and break up the fruit skin more to allow the flavors to escape into the beer.
There is a presence of alcohol and a lower pH level. This isn’t a great environment for bacteria growth, therefor being less susceptible to contamination.
wait, we are talking about a sour beer here right? it’s going to be infected right? so what’s the worry. with the low pH and moderate alcohol content of the mostly finished beer it’s unlikely that anything really unpleasent is going to happen. Cooked fruit is not going to taste anything like raw fruit you can steam them or soak them in sanitizer to kill stuff on the outside if you want. still no guarantees but that is sour brewing with fruit.
You only want to age sour beer on fruit for a few months so adding fruit right after primary fermentation ends means you’re going want to bottle it within 4-6 months due to the fruit but the beer itself may not be ready by that time. You would be better off freezing the fruit and adding it after about six months.
Otherwise, a sour mash beer or a beer just soured with lactobacillus would be a better option if you want to use the fruit right away.
I am curious as to why you say this? is there concern with tannins? As Iunderstand it traditional fruit lambics are aged on the fruit for many many months. often there is nothing left of the cherries but the pits.
I had a bottle of the Almanac Brewers reserve which was aged in a wine barrell on plums and cherries for a year before bottling. It’s delicious
Like with hops you can lose some of the fresh character of the fruit after a few months. Cherries hold up really well to long term aging on the beer but they seem to have a unique staying power. Admittedly, I’ve never used plums in a sour beer so I’m not sure when it’s best to pull them off. Apricots tend to be aged for only a few months, even by the largest lambic brewers.