Freeze Your Sour Cream for Later. Sour cream is usually good for about three weeks after its been opened. If youre too busy to make anything with your sour cream now, freeze it until you have more time. While freezing changes the texture of sour cream a bit, the difference is undetectable in cooked dishes. Just tuck the tub in the freezer until you get some free time, or discover you need it for a recipe. Did You Know You can use leftover sour cream as the starter for a fresh batch of sour cream. Give it a try, and youll be amazed at how easy it is to make your own sour cream, and how much better it tastes than the store bought stuff. It only takes two ingredients and about a minute of your time. How to Make Sour Cream from Scratch. Switch to Powdered Sour Cream. If you never seem to have sour cream on hand when you need it, or you always struggle to figure out what to do with the leftovers, consider making the switch to powdered sour cream. It can be reconstituted just like powdered milk, whenever you need it, and in whatever quantity you need it. You probably wont find it in your local grocery store since its sort of a specialty item, but its easy enough to order online. Buy Powdered Sour Cream on Amazon. Think about adding powdered buttermilk and powdered heavy cream to your pantry too. Its nice to have what you need on hand when you find a recipe that you want to make, and its just as nice to free up some space in the fridge. Since I switched to powdered dairy products, I have considerably less waste to deal with. I just mix up exactly what I need for a recipe, and return the container to the pantry until next time. See Also Sour Cream Substitute.