Buttermilk (Best Option)
1 cup buttermilk per 1 cup whole milkButtermilk contains lactic acid and proteins similar to whole milk, which help strengthen gluten networks in bagel dough, essential for the chewy texture. The acidity also reacts with baking soda or yeast to improve rise and crust color.
When using buttermilk, reduce any additional acidic ingredients slightly to maintain balance. The dough may require a slightly longer kneading time to fully develop gluten.
Compared to whole milk, buttermilk produces bagels with a more pronounced tang and slightly denser crumb, which many consider traditional and desirable in bagels.