How many gravity points does a pound of berries contribute to a 5 gal mead batch if used in the primary?
The berries were a combination of frozen blackberries, blueberries, and red raspberries.
Does 6 lbs in the primary and 6 pounds in the secondary sound like too much?
I don’t know their sugar content, but unless we’re talking about a fairly small, dry mead, no I would not consider 12 lbs too much in 5 gallons. If a really big, sweet mead I’d probably go even higher.
Blueberries generally add little flavor in mead. I don’t have any specific experience with blackberries, but IIRC they don’t add that much flavor. Raspberries do add a lot of flavor. Assuming raspberries are only a relatively small part of the berry mix (<1/3), I don’t think 12 lbs of the berry mix to be excessive.
While berries will add fermentables to the mead, the berry juice is likely to contribute a lot less sugar than the honey unless you are making a “session” mead.
Berries are mostly composed of water. The amount of sugar added will likely be offset by the amount of water that they add to your mead. I was once told that in some instances, depending on the fruit, that adding the fruit will actually subtract gravity points due to the water content that they add. But I think the difference either way will be insignificant.
Blackberries and raspberries don’t yield much puree/juice - Last I pureed 2 lbs of blackberries and only got 24 oz of juice.
I would puree/strain half and add to primary. After primary, taste it to figure out how more flavor you want. You can always add puree to secondary in doses until its where you want it.
If you add the whole fruit, that’s true. I would plan on it being a wash, unless you have particularly juicy and sweet fruit.
12lbs sounds a bit on the low side. I used 10lbs of blackberries, and my mead was kinda pinkish when it was done. I’d probably use twice that much if I brewed it again.