I've been looking into whether frozen blueberries/raspberries should be thawed or not when mixing with batter to prevent bleeding. What's the deal??? Is it best to thaw, mix frozen, add flour after thawing, add flour when frozen... I'm confused!
Thaw. They well produce a lot of liquid when they thaw. You can use the liquid in place of the liquid in your recipe, or you can drain at that point and dredge with the flour. I'm not sure you'll completely avoid bleeding though.
Defintely thaw, it will produce alot of water as pmarks0 said which just makes water down batter and it takes longer to cook, it will bleed regardless but fold instead of mixing or stiring, it will help the bleeding.
I'm the opposite. In muffins, I use them frozen and covered in a mixture of sugar and flour. The result is an intact berry, not baked, but that is what I was after. These berry muffins are, by a long shot, my most requested item on a menu that offers over 150 items. I have never baked them in a cake, but you are only talking another 8 minutes of baking. I don't have bleeding because the berry didn't pop. The juice is still in the berry, to be enjoyed by the person who bites into it. I have not tried this with strawberries, which I am sure would fail.