Sauce in a sealed jar smells off, has it gone bad?
It is far more likely that the ricotta has gone bad. If your nose picks up off smells, you should generally trust it.  The best time to take a sniff is right when you pop the jar open. We change ricotta's water everyday and try to finish it within a couple of days. I've also seen many freshly openned ricotta (well inside the expiry date) that had gone bad, and didn't look bad. 

Another thing you can do when you cook for others is to taste your food in small samples along the way. That way you get feedback and don't surprise yourself (or others).  Use two spoons (one to pull food sample and dollop on the second spoon that you taste). That way you don't contaminate the food.