Milk + Lemon Juice or Vinegar (Best Option)
1 cup milk + 1 tablespoon lemon juice or white vinegar (let sit 5-10 minutes)This substitute works because the acid (lemon juice or vinegar) curdles the milk slightly, lowering its pH to approximate that of buttermilk. The acidity helps activate the yeast and tenderizes gluten, which is crucial for yeast bread structure and crumb.
For best results, use whole or 2% milk and allow the acid to react fully before adding to the dough. Avoid using skim milk as it may reduce tenderness. Ensure the mixture is fresh and not overly curdled.
Compared to original buttermilk, this substitute yields very similar dough elasticity and rise, producing a bread with comparable crumb softness and flavor.