Q: When I make juice from fresh tomatoes, it separates. Is there some way I can keep that from happening?
A: Like many fruits, including apples, tomatoes have natural pectin that helps the cell walls stick together. But when you cut or crush the tomatoes, you release an enzyme that attacks the pectin, making the cells separate.
To stop that, you have to “turn off” the enzyme by exposing it to heat. Since it’s hard to heat the tomatoes quickly enough with home equipment, there is a trick to that.
First, take just a few of the tomatoes and cut them into quarters or halves. Place those in the pot and heat while crushing them. Once you’ve brought the mixture to a boil, continue adding the rest of the tomatoes cut into large chunks, crushing them as you add them. Keep them boiling until you’ve added all of the tomatoes, then simmer 5 minutes longer.
Continue with the recipe, following the directions for safely canning the juice, and it should stay together.