Buttermilk
An acidic dairy liquid that tenderizes gluten and activates baking soda for a light, airy rise.
1 Cup Buttermilk = 240 mL • DIY: 1 Cup Milk + 1 Tbsp Lemon Juice/Vinegar (let sit 5 mins)
Buttermilk was originally the liquid left behind after churning butter from cultured cream. Today, commercial buttermilk is produced by inoculating low-fat or skim milk with lactic acid bacteria, which ferment the lactose into lactic acid. This fermentation process thickens the milk and gives it a distinct tangy flavor. In baking, buttermilk is highly valued for its acidity (pH around 4.5). Lactic acid breaks down and weakens gluten proteins, resulting in an exceptionally tender, soft crumb in quick breads, pancakes, biscuits, and cakes. Furthermore, the acid reacts instantly with alkaline baking soda to produce carbon dioxide bubbles, acting as a powerful leavener.
Historically, recipes also used scalded milk to deactivate whey proteins that weaken gluten, but buttermilk's acidity naturally improves dough stability without scalding. If you do not have buttermilk on hand, a common DIY substitute can be made by adding an acid like lemon juice or white vinegar to fresh milk, curdling it slightly to mimic buttermilk's acidic properties.
Substituting regular milk 1:1 for buttermilk in a recipe that calls for baking soda. Without the acid in buttermilk, the baking soda cannot activate, resulting in flat, dense bakes with a bitter taste.
In the US and UK, cultured buttermilk is standard. In Scandinavian countries, traditional varieties like filmjölk behave similarly in baking.
Essential for soda bread, pancakes, waffles, Southern biscuits, red velvet cake, and marinades for fried chicken.
Replace 1 cup buttermilk with 1 cup milk + 1 tablespoon lemon juice, or 3/4 cup plain yogurt + 1/4 cup milk.
Refrigerate for up to 2 weeks. It can also be frozen for up to 3 months, though it may separate upon thawing whisk to recombine.