What is the key difference between baking powder and baking soda, and when is each used in pastry?

• A. Baking soda needs an acid to react; baking powder contains acid and requires only moisture.
• B. Baking soda needs an acid to react; baking powder contains acid.
• C. They are interchangeable in all recipes.
• D. Baking soda is never used in pastry.

Answer: (A)

Leavening depends on how the chemical reacts with other ingredients. Baking soda is pure sodium bicarbonate and needs an acidic component in the batter to produce carbon dioxide and lift the dough. Without acid, it won’t rise and can leave a soapy or metallic taste if used alone. Baking powder already contains both an acid and a base (plus a drying agent), so it just needs moisture to start reacting, with a second rise typically occurring from heat in most double-acting blends.

That’s why this option is best: baking soda needs an acid to react; baking powder contains acid and only needs moisture (and heat for the second stage in many powders). In pastry, use baking soda when the recipe includes enough acid (yogurt, buttermilk, lemon juice, vinegar, brown sugar, etc.) to activate it and contribute browning and tenderness. Use baking powder when there isn’t enough acid in the batter or you want a reliable rise without adding extra acidity.