I added 3 lbs frozen berries to a 5 gallon batch of porter. Racked over the berries in secondary, and let it sit for two weeks.
While the porter turned out great, there is barely any perceptable blackberry flavor. Although the brew did take on a nice purplish hue.
I was trying to recreate a buddy's blackberry porter, where he used fresh blackberries at a rate of 1 lb per gallon of beer. He added it to the primary about a week after pitching the yeast, and it turned out great.
I'm trying it again, but this time with a 3-lb can of Oregon raspberry puree. I added it to the primary last night, about five days after pitching yeast. Fermentation had pretty much quit, but this morning there was fresh action in the vessel (krausen and airlock).
Hey, first post!