In early January this year, I picked up a large can of San Marzano tomatoes from Costco and made some tomato sauce - added onions and garlic sauteed in olive oil. I divided them in several glass jars and stored them in the garage (in winter, my garage is my other fridge). Went through the jars pretty quickly, in a matter of a couple of weeks. But then yesterday, I was going through the garage and found one jar left, completely overlooked as I shuffled around the jars!! I don't see any mold, nothing white, and it smells/tastes of a slight tartness that could be from the garlic. Is it bad? Any way of knowing if it's bad or should I just give it a good boil?