Grapes are almost past now. If your in Z6 they might be dropping off vines. Concords are quite common and can make a nice jelly if they are not spoiled or whithered. Concord grape wine is a bit 'foxy' unless its made with other milder grape types too. The frost may have caused them to drop off, as they do contain quite a lot of liquid inside.

I've never seen a prohibition on canning any after-frost fruit except tomatoes. Did you see the thread on "table-ripened tomatoes" where Carol posted the details on Penn State's somewhat less restrictive rules on which tomatoes are ok? It seems to relate to end-of-season blight...is there something similar in grapes?

The concerns with tomatoes are 1) higher pH, which shouldn't be a problem since grapes start at a much lower pH than tomatoes, and 2) frost-damaged cells can be more susceptible to fungus. I don't know whether that applies to grapes. I hope someone with experience will join in. I can't tell from Ken's reply whether he's ok with canning after the frost or whether he's just talking about concords in general.

Melissa

Well ended up with 2 bushels. I would say about ~5% of the ones I picked were past their prime being very very dark, almost black in color, with an almost leathery texture and none of the white/silvery opalescence of a prime concord. Two people and 4 hours later they are cleaned and simmering in 2 very large canning pots. As Lynyrd Skynyrd sung... "Ooh that smell!" Expecting about 50 jars of jelly out of the batch, 50% are pints and the other are half pints.

The whitish silver color on the grape skins is natural yeast formation. Its also seen on frsh blueberries. The yeast is also a protective layer that blocks some bad yeasts and molds for a short time. Carefully removing that yeast can give you a nice yeast based bread too. If you use a Villaware/Roma food strainer, be sure to use the shorter grape spiral as the default one can jam with the big grape seeds. The food strainer also removes all traces of skins as well. A fast, great way to make juice out of grapes. No need to cook beforehand either!

The tradition in our family is to always wait until the first frost to harvest the Concords. The juice/jelly/wine has always been wonderful. Just don't let them freeze through or they'll ferment on the vine!