Can you believe how click-baity that title is? (Is it still click bait if the post actually lives up to the title?) In fact, I plan to deliver on the promise of that title, because if you’ve gone to the trouble of foraging for wild/feral grapes, juicing them, and straining the juice, I don’t want you to make this major grape jelly mistake.
Here’s the science-y part: Grape juice differs from many other fruit juices in that it contains large amounts of both potassium and tartaric acid. At temperatures below 40F, these substances bind together to form crystals of potassium bitartrate, and if those crystals aren’t removed from the juice, you’ll end up with crunchy bits floating in your jelly. It’s perfectly safe to eat (in fact, cream of tartar is finely ground potassium bitartrate), but who wants crunchy jelly? Not me.
Fortunately, this problem is easy to solve; all it takes is time and a fine strainer. The instructions below pertain to all grapes: foraged, garden-grown, store-bought, white, red, and purple!
How to Eliminate the Crunchy Bits
After you’ve strained the fruit and collected the juice, pour the juice into containers, cover them, and refrigerate for 24 – 48 hours. I’ve read suggestions that 12 – 24 hours is enough, but I’ve found many more additional crystals form after the initial 24 hours, so go for the full 48 if you can stand to wait. Then, slowly pour the juice through a jelly bag or cheesecloth, into a new container, being particularly careful as you reach the bottom of the original vessel. Here’s what you’ll find there:
Once you’ve eliminated the tartrate crystals, your juice is ready to turn into jelly, or syrup, or just enjoyed as juice. And you can rest assured no one will find unwelcome crunchy bits in their PB&J sandwich. Disaster averted.