Kitchen Notes: Canning Unsweetened Fruit Juice

I thought about making a mixed berry jam using the berries that have been in the freezer; but my pantry currently suffers from a glut of uneaten jams. To convert this into the base of a drink spritzer, take an equal amount of a basic sugar syrup (1:1 ratio of sugar to water, boiled together and volume reduced by half) and add it to the juice. Then add up to a 1/4 c of the juice mixture to a glass with ice and sparkling water (or sparkling wine).
TheFoodening Blog - Unsweetened Mixed Berry Juice

I just needed to free up some freezer space for my dumplings. 
Anyhow. Onto the process.

This batch had a lot of seeds! OMG. So many tiny seeds to filter out. I batch strained the solids 2-3 times (the -3rd time was the thick goo leftover in the strainer and I let it drip out overnight in the fridge in a bowl).

1/2 lb boysenberries, from the farmers market - big, ripe and not really sweet
1 lb strawberries - uhh, I froze them whole so the stems were still there
1 qt blueberries - these have been in the freezer for a while, a couple years; picked at Majestic Farm Blueberries a few miles away

I am not sure why I tossed in the remainder of an opened jar of Fonseco port, but a bit more than a cup of port is also in this "juice".

Crock it all together in a slow cooker for a few hours on LOW.

Made: 5 half pints