Canning vegetable broth
Meat broths all say 20 minutes at 10lbs for pints. I can't find any consistent answers for vegetable broth. A lot of sites say 75 minutes, which is the time for vegetable soup, which contains solids. Vegetable broth does not.
Is it safe to can vegetable broth at the 20 minutes?
If not, why is the same broth that was made with bones and meat able to be canned at a much shorter time?
The best bet for you might be to use the tomato-vegetable juice recipe. There are no recommendations for a vegetable broth that I have found. For a safe product, keep the amount of tomatoes in the recipe at the same level. The acid in tomatoes is part of the preservation. Follow this link to the recipe and full instructions from the National Center for Food Preservation. The processing time for quarts in a pressure canner at 15 pounds pressure is 10 minutes.
Most all vegetable broth recipes contain no tomatoes at all. I don't want to make tomato juice since the recipes I use that use vegetable broth would be ruined by the flavor and acidity of tomatoes. I will stick with the times and weight from meat stocks since no one has an answer and it makes sense that a similar liquid minus meat proteins and collagen would have a similar if not lessened processing time.
I am so sorry that I wasn't able to find canning times for vegetable broth! But if the National Center for Food Preservation doesn't have them, it might mean that they did not do research on that particular recipe. Since improper canning increases the risk of botulism, it is best to only use approved recipes. Of course it would be perfectly safe to freeze the vegetable broth instead.