Canning grape juice

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Old Philosopher

Oct 22, 2009
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Greetings to all after a long absence!

I have a mystery on my hands. In lieu of making wine this year, I elected to can some fresh grape juice.
We chose two different methods: 1) simmering and draining the grapes (as in jelly making), and 2) cold-pressing the grapes, straining and pasteurizing the juice.
Method #1 yielded a nice amber product, similar to grape jelly, but liquid, after hot water bathing (per recipe) for 20 minutes.
Method #2 resulted in a very clear, wine-like liquid after the hot water bath.

Problem is, Method #2, using cold-pressed grapes, left us with a pile of mysterious sediment in the bottom of each quart jar! Not just cloudy sediment like you'd get when allowing wine to 'clear', but a literal pile of cohesive 'gunk'.
The juice was not perfectly clear when we put it in the jars (neither method produced clear juice), but the juice from the cold-pressed grapes produced this material at the bottom of extremely clear juice.

Has anyone experienced this? What the heck IS it? My research has shown me pictures of "tartaric flowers" formed in juice many years old, but no explanation of what happened to our fresh juice. The juice was heated to 190F for 5 minutes to pasteurize it, and none of this sediment appeared. After 20 min in the canner (at 210F), we got the sediment. Did we "cook" all the suspended sediment, and have it accumulate in the bottom of the jars? Why didn't that happen to the juice that was NOT pressed?

HELP! Did I just waste 5 gallons of fresh grapes, or do I siphon off the clear juice and re-can it?