Skip to content
Know.itKnow.it
Create an animated lesson
On request

This article is free to read. Creating a lesson uses your daily or stored credits; review the language and settings before starting.

How does baking soda work in baking?

ScienceLesson on requestFree to read

Quick answer

Baking soda is sodium bicarbonate, an alkaline powder. When it is mixed with an acidic ingredient such as yoghurt, buttermilk or lemon juice, it releases carbon dioxide gas. The gas forms bubbles in the batter, oven heat expands them, and the batter sets around them to create a light, airy texture.

Baking soda works by reacting with acids in a batter to release carbon dioxide gas, which forms bubbles that make cakes and quick breads rise. Oven heat expands those bubbles and then sets the surrounding batter, locking in a light, airy texture.

Step by step

  1. Baking soda is mixed into the dry ingredients so it spreads evenly through the flour before any liquid is added.
  2. Wet ingredients containing acid are stirred in, starting a reaction that releases carbon dioxide bubbles into the batter.
  3. The batter is placed in a hot oven, where heat makes the gas bubbles expand and moisture turn to steam.
  4. Expanding gas and steam push the batter upward, while any leftover soda breaks down and releases a little extra gas.
  5. Proteins and starches set firmly around the enlarged bubbles, holding the risen shape as the cake or bread cools.

Key things to understand

  1. Baking soda is sodium bicarbonate, a mild alkaline powder that holds carbon dioxide inside its chemical structure.
  2. When it meets an acid such as buttermilk, yoghurt, lemon juice or vinegar in wet batter, it releases carbon dioxide gas.
  3. Mixing traps the gas as tiny bubbles in the batter, while beating also adds small air pockets for the gas to enlarge.
  4. In the oven, heat makes the bubbles expand and turns water into steam, pushing the batter upward.
  5. Eggs, flour starch and proteins then set around the bubbles, fixing the rise into a soft, porous crumb.

Labelled diagram

  1. Baking soda

    Sodium bicarbonate, an alkaline powder mixed into the dry flour.

  2. Acid

    Buttermilk, yoghurt, lemon or vinegar reacts with soda once liquid is added.

  3. CO2 bubbles

    Released carbon dioxide gathers into small bubbles spread through the batter.

  4. Oven heat

    Heat expands bubbles and turns water to steam, lifting the batter.

  5. Set crumb

    Proteins and starch firm up around the bubbles, fixing the airy texture.

How baking soda makes a batter rise

Real-world examples

  • Gujarati khaman dhokla gets its spongy texture when a soda-based fruit salt reacts with citric acid in the batter.
  • American buttermilk pancakes rise because the buttermilk's lactic acid reacts with baking soda in the mix.
  • Chocolate cakes made with natural cocoa rely on the cocoa's acidity to activate baking soda.
  • Irish soda bread uses baking soda and buttermilk instead of yeast, so it can be baked straight after mixing.

Common mistake

✗ Myth: Baking soda and baking powder are the same thing and can be swapped freely.

✓ Fact: Baking soda needs an acid in the recipe and is several times stronger, while baking powder carries its own acid. Swapping one for the other without adjusting amounts and acidity often gives flat, bitter or soapy results.

People also ask

What does baking soda do in a cake?
Baking soda acts as a leavening agent. It reacts with acidic ingredients in the cake batter, such as buttermilk, yoghurt or cocoa, releasing carbon dioxide bubbles. In the oven those bubbles expand and the batter sets around them, giving the cake height and a tender, open crumb. It also helps the crust brown.
Can i use baking soda without an acid?
Only partly. Heat alone breaks baking soda down into carbon dioxide, water and sodium carbonate, so some rise still happens. But without acid to neutralise it, the leftover sodium carbonate makes the food taste bitter or soapy and can discolour it. Recipes using only soda therefore always include an acidic ingredient.
Why do you add vinegar to baking soda?
Vinegar is acetic acid, and it reacts quickly with sodium bicarbonate to release carbon dioxide gas. In eggless cakes this gives a fast, strong rise to replace the lift eggs would provide. The reaction also neutralises the soda, so the finished cake does not taste soapy, and little vinegar flavour remains after baking.
What is the difference between baking soda and baking powder?
Baking soda is pure sodium bicarbonate and needs an acid in the recipe to react. Baking powder already contains baking soda plus dry acids and starch, so it rises with just moisture and heat.
Why does too much baking soda taste soapy?
Excess soda that finds no acid to react with breaks down in the oven into sodium carbonate, a stronger alkali. That leftover alkali gives a bitter, soapy or metallic taste and can turn the crumb yellowish.
Why should batter with baking soda go in the oven quickly?
The reaction with acid starts as soon as the wet and dry ingredients meet. If the batter sits too long, much of the gas escapes before the oven sets the structure, giving a flatter, denser result.
Why does baking soda make baked goods browner?
Baking soda raises the alkalinity of the batter, and alkaline conditions speed up the Maillard reaction between sugars and proteins. That reaction creates brown colour and toasty flavour, so cookies with soda brown more deeply.

Part of the guide: Food & Kitchen Science →