You can add LorAnn flavorings to unflavored juice as long as you aren't using the ones with oils in them that's generally considered not great.
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With that said, it sounds like you purchased the flavorings recommended for e-juice and not the food-oriented ones (if I am recollecting correctly, LorAnn does have some of both). I'd start small and work my way up, you can underflavor and fix that, but it's much more of a pain to try and dilute down your ejuice that is overflavored....
You may want to check out the DIY board for more info, and I think there may be a thread dedicated to those flavorings as well as some recipes, though I myself just started with single flavorings and combined in my tank after reading a lot of recipes then went creative from there... It's how I learned to cook, so it kind of made sense to me.
Best of luck, and I hope you enjoy your flavorings, you may need to let them steep for a while to bring out the full flavor effects.... Hope it goes well.
Ann