Unsweetened Concord Grape Juice
I would prefer to preserve Concord grape juice unsweetened and I have seen recipes for such. I am hoping you can provide clarification why no added sugar is necessary for preservation safety. Usually there is much focus on acidity and/or sweetness in canning recipes for other produce. I am confused why this seems immaterial to grape juice. Is it because there is an assumption that the grape juice has a natural sugar level that satisfies this requirement? I would appreciate any detailed explanation you can provide.
Where did you find the information about sugar being required for grape juice?
The primary concerns in canning relate to the pH level of the food products not their sweetness.
Sugar has does not affect the pH level of a fruit.
The only reasons sugar is added to fruits is: for sweetness; to help retain the shape of the fruit; to improve the flavor: and to stabilize the color.
Fruits may be canned without sugar.
But since you are canning grape juice, the reason for retaining the shape of the fruit does not apply.
Therefore sugar is not necessary for the canning of grape juice.
It is important to use standardized recipes from the U.S.D.A. Guide to Home Canning or The National Center for Home Food Preservation-So Easy to Preserve, or a State Extension Service. All other sources are considered questionable.
If you have other questions do not hesitate to contact me. Sincerely,