If you’re not sure if the tangy smell is normal, check for other signs of spoilage before you toss or use the buttermilk.
For instance, buttermilk might develop pink, gray, or fuzzy patches if it’s bad.
If it’s really warm where you live (over 90 °F (32 °C), play it safe and throw away buttermilk that’s been left out for 1 hour or more since bacteria grows faster at warmer temperatures. If the buttermilk’s been out over 2 hours, it’s best to toss it—you don’t want to risk dangerous bacteria that can cause severe illness.
Keep the buttermilk in the main body of the fridge, not the shelf door since it’s too warm there. Ensure that your fridge is set to 40 °F (4 °C) or below to extend the shelf life of the buttermilk. For longer storage, freeze buttermilk for up to 3 months. [6] X Research source Then, thaw it in the fridge overnight before you bake with it.
If you’re a little concerned about using the buttermilk, use it in a baking recipe so it will be cooked at a high temperature.
Some people might get more serious poisoning if they ate a lot of bacteria or if they’re immunocompromised.
