I don't know about the glycerin, but if you are wanting to avoid alcohol, you do realize that the alcohol evaporates off. Even if added at the last minute, you could simply add it a minute or two earlier to make sure it escapes before canning. I have hear that some folks are so sensitive that even a little residual is problematic, so I understand if you are trying to be super careful.

I don't see why you couldn't use extracts... here is a link to where almond extract is *optional in several recipes provided vie a county extension web site. Notice the amount 1/4 teaspoon per quantity of other ingredients, so it doesn't take much to flavor a batch. What extracts and fruits are you considering? Just curious... :)

canfan - I have a GF baking business so there sit a lot of extracts (nothing artificial) that I buy in bulk, and I make about 50 varieties of fruit jam so I'm always looking for a new flavor combo. I noticed that most of the extracts use alcohol, not the problem, but a lot have glycerin in them too, which is the unknown for me as far as using it in canning.
BTW pure almond extract is usually just almond oil and alcohol.
Nancy