A reader's recipe for Banana Muffins calls for 1/3 cup buttermilk. He hates drinking the stuff and wonders what is the best substitute, because he has no intention of buying a quart or half-gallon of buttermilk to get 1/3 cup.
Some supermarkets stock pint cartons of buttermilk, but I can never seem to find any when I need one. If yogurt is on hand, that's a dandy substitute. For baking purposes, 1 cup buttermilk is equal to 3/4 cup yogurt plus 1/4 cup milk or water; add liquid gradually and stir gently.Another substitute is "soured" milk. To make it, add 1 tablespoon lemon juice or vinegar to 1 cup fresh sweet milk. Stir and let stand a few minutes to thicken. Note that you start with fresh milk; never use milk that has turned sour over time: It has spoiled and must be discarded.
One final opinion: Nothing beats buttermilk for adding flavor and tenderness to baked goods. Neither soured milk nor reconstituted buttermilk powder seems to produce the same high quality, though recipes are acceptable made with either.
Never substitute regular milk for buttermilk in recipes, because leavening requirements are different; some soda is necessary to balance the acidity of buttermilk, yogurt, "soured" milk or sour cream.
If you have buttermilk left over - and no volunteers to drink it, don't forget how easy it is to make buttermilk pancakes. They're at least 10 times better than any pancake mix and not much more trouble.
Here's Betty Crocker's buttermilk pancake formula: Beat an egg with a hand-beater or wire whisk until lightened with air - almost fluffy. Beat in 1 cup flour, 1 cup buttermilk, 1 tablespoon sugar, 2 tablespoons oil, 1 teaspoon baking powder, 1/2 teaspoon baking soda and 1/2 teaspoon salt. Grease a heated griddle. Splatter with some water droplets; when they skitter around, griddle is hot enough.
For each pancake, pour about 3 tablespoons of the smooth buttermilk batter onto hot griddle. Cook until pancakes are puffy and dry around edges. Turn and cook other sides until golden brown. You'll end up with about nine delicious pancakes and a lot less buttermilk going to waste. - Joyce Rosencrans