I have had a container of off-brand sour-cream I bought from the grocery store in my refrigerator for almost two months. When will it go bad or will is ever go bad?
Eventually, yes... but it does have a fairly long shelf life.
According to Eat by date, you should expect 1 to 2 weeks after the date on the package. They say:
You can tell if sour cream has gone bad if you notice dark mold on its surface, bright bacterial marks, pockets of watery liquid and a sharp, bitter flavor. First the liquid will begin to separate, at which point it can still be used but within a week you will need to throw it out when you notice mold on the inside of the lid and then in the product.
Yes. Foods are specially designed for sale. Soured cream has been artificially soured for sale. After that is just goes off. It is like blue cheese, the 'blue' is artificially injected into the cheese. You could personally scrape off the mould but it is not the sort of thing you can/should serve to someone else.
It lasts a really long time. I bought a tub two months ago and used two table spoons. The expiry date was 1 1/2 month ago. I opened it and there was no mold, no variation in colour and very little liquid separation. I smelled and and tasted it and it was fine. I used it in mash potato. Yum!! And, no, we did not get sick. They key is to use clean utensils, not your fingers, to prevent contamination. Same goes with yogurt. Don't worry so much about expiry date. Use your senses (smell, look, taste).