Pick an ingredient once, then search with as many words as you like — every product gets an Add button for it.
Certainty is how sure the model is that a product is the ingredient: 5/5 at 98% or more · 4/5 95–97% · 3/5 90–94% · 2/5 80–89% · 1/5 under 80%, usually a substitute. Checked means you marked it OK.