[header] How to freeze buttermilk [title] Portion out the buttermilk into usable amounts. [step] This amount may change depending on what you use the buttermilk for. You might find 1/4 cup (2 oz) portions ideal, or you may prefer 1 liter (. 26 gallon) portions. 
Write down what recipes you plan on using the buttermilk for and pick the most common amount. [substeps] You might freeze bags of varying sizes so your portions fit many recipes.