Blackberry port is seldom made, but well worth the effort. Use fully ripe berries, fresh or frozen. Makes one gallon (4.5 L).
Wash and crush the blackberries in a nylon straining bag and strain the juice into a fermenter. Tie the top of the straining bag and place in a fermentation vessel. Stir in the remaining ingredients, except the pectic enzyme, yeast, and red grape concentrate. Stir well to dissolve any residual sugar, cover, and set aside for 8– 12 hours. Next add the pectic enzyme, re-cover, and set aside for an additional 8–12 hours. Add the yeast and cover. Stir the ingredients daily, and press the pulp in the nylon bag to extract flavour.
When specific gravity is 1.030 (about 5 days), strain the juice from the nylon bag and rack off. Fit an airlock and set aside. Rack off again after three weeks and two months after that. When the wine is clear and fully fermented, stabilise and add the red grape concentrate. Set aside for another 3 weeks. If no further fermentation occurs, rack the wine again, and bottle. Allow at least a year to mature. This recipe will continue to improve for several years.