We also make grape jelly, in our case from Concords, and have used a
steamer/juicer. The reason we stopped using it is that the steamer
actually adds more water to the juice than simply heating the grapes to
the boiling point. When we heat up grapes for jellymaking, we add only
the tiniest amount of water to the bottom of the kettle, just as we do
for applesauce. Then we heat very slowly, to avoid scorching, and the
grapes themselves turn to liquid. The steamer juicer works by keeping
the fruit surrounded by steam, which condenses on the fruit and runs out
with the juice, resulting in substantial dilution.
Don Yellman, Great Falls, VA
[NAFEX] Steamed Grape Juice,
Don Yellman, 01/01/2004