Our food perishes because bacteria are attracted to its nutrients. Your nose is often the best gauge when determining edibility, but if you are still uncertain, do a taste test and sample a bit of the food in question on your tongue — without swallowing it! If you have the urge to spit it out (or worse), then trust your clever taste buds and toss it right away. It is always better to be safe than sorry.

http://www-ehs.ucsd.edu/food/FFA0211_FoodSafety.pdf