I made some quick apple jelly last night and it didn't set (though all the jars sealed well). I'm not exactly heartbroken over this, since I only wanted some to use as an ingredient; I like jams and preserves, but jelly is just meh. Anyway, since the jars do have the vacuum seal (tested this evening), can I keep the jars for the next time a recipe calls for apple jelly? Most of my recipes using the jelly as an ingredient call for the melting of the jelly anyway (or it will melt at some point, as in a sauce recipe).
I'm pretty sure I know where I went wrong--not having that solid, can't stir it down boil before I added the liquid pectin. And I used store-bought juice instead of making my own.