Many recipes call for buttermilk and then recommend curdling regular milk with vinegar or lemon juice. This certainly makes lumpy, sour milk that works for a citrusy recipe like Loaf-Pan Lemon Cake. But in something like the buttermilk glaze for Sourdough Cinnamon Rolls, you’ll taste the acid and miss cultured buttermilk’s rich flavor.
Cultured buttermilk is even easier to make than yogurt, because it ferments on the counter at room temperature. It does call for one special ingredient: a mesophilic starter.
Like active-culture yogurt, a starter acidifies milk so that good bacteria grow and flavor develops. Mesophilic starters work their magic at low temperatures, 68°F to 102°F, and different bacteria combinations produce specific cheeses, from soft fromage blanc to crumbly feta to firm cheddar.
If you use buttermilk often, a powdered buttermilk starter from a source like Cultures for Health lets you create a mother culture to reuse weekly. Mix this type of mesophilic starter once into fresh milk and then treat it like you do homemade yogurt, saving a small amount to culture the next batch.
I prefer direct-set mesophilic starters, which I buy at Withey’s Health Foods or online. You use a little of these freeze-dried, powdered cultures each time you make a dairy product, but they last for years in the freezer.
My freezer holds several tiny bags of direct-set mesophilic starters, with names like Meso II, Aroma B, MM 100 and MA 4001, so that I can make specific cheeses. But buttermilk isn’t picky: any of these starters turns pasteurized whole milk into cultured buttermilk. As with homemade yogurt, avoid ultrapasteurized milk. Choose “cream on top” milk if you don’t mind stirring a thicker surface layer back into the buttermilk.
Cultured Buttermilk
Makes 1 pint
2 cups cold whole milk
1/16 teaspoon powdered mesophilic starter
Pour the fridge-cold milk into a wide-mouth glass pint jar. Pour warm water into a 3-quart or larger thick-bottomed saucepan until about two-thirds full. Set the jar of milk in it, ensuring the water level is below the jar threads. Let it sit for about 30 minutes, until the milk and water are the same temperature, between 76°F and 86°F.
Sprinkle the powdered starter over the milk and wait five minutes for it to rehydrate. Use a fork to stir in the starter, making about 20 up-and-down strokes to distribute it evenly.
Set a clean canning lid loosely on the jar; if your kitchen temperature is below 70°F, loosely cover the pot with a lid. Leave the jar in the water bath for up to 12 hours so that the milk cools slowly and starts to thicken.
Remove the buttermilk jar from the water bath and screw on the lid. Leave it at room temperature for another six to 36 hours, until the buttermilk ripens to your desired thickness and tanginess. Use immediately or refrigerate for another eight to 12 hours to develop fuller flavor. Store cultured buttermilk in the refrigerator for up to two weeks.
Julie Laing is a Bigfork-based cookbook author and food blogger at TwiceAsTasty.com.