Wild fruit seems to have a tendency to spoil the beer easier if you don't sanitize it. If you pasteurize the fruit, make sure you stay In proper temps (IIRC, 150-170) and use pectin (search how to use it, I've only had a bad experience with NOT using pectin and ending up with a lot of haze, and have heard lots of praise for pasteurization and pectin. I tend to freeze store-bought fruit, throw it in the secondary, and rack right on top. However, I have had bad experiences with wild picked fruit. Even on a fully fermented 6.5%abv beer, the beer formed a moldy-ness on top. I was able to rack into priming and leave the funk behind once, and one other time it didnt save the beer from being nasty. I am going to be adding fruit to secondary soon, wild mulberries that I froze. I think im going to give them a soak in sanitizer, then rinse with sterile water, then throw em in.
With blueberries, I would do the above with the whole fruit, don't puree or cut them.
Good luck!
