What is buttermilk?
You might be surprised to know there is no butter in buttermilk, and it has less fat than regular milk. It is liquid that is left after butter has been churned and tastes slightly sour. It's thicker than regular milk but not as thick as cream. Most people don't churn their own butter, so buttermilk sold in stores is processed by adding a culture to regular milk and letting it ferment.
How should it be stored?