What is it?
E500 covers three related mineral salts: sodium carbonate (washing soda), sodium hydrogen carbonate (bicarbonate of soda, baking soda), and sodium sesquicarbonate (a hydrated mix of the two). All are naturally occurring compounds of sodium, carbon, and oxygen. Sodium bicarbonate is the form most commonly used in food.
What does it do?
In baking, sodium bicarbonate reacts with acids in a dough or batter (such as buttermilk, yoghurt, lemon juice, or acidic raising agents) to release carbon dioxide gas, which causes the mixture to expand and lighten. Sodium carbonate is more strongly alkaline and is used to raise the pH of foods such as cocoa powder (Dutch-processing) or noodles, altering texture and flavour. As an acidity regulator, the salts buffer a product to a target pH. As an anti-caking agent in dry mixes and powders, they absorb moisture and keep particles free-flowing.
Where you will see it
Most commonly found in biscuits, cakes, scones, bread, crackers, and other baked goods as a leavening agent. Also used in cocoa powder processing, Asian-style noodles (giving them a chewy yellow texture), fizzy bath products, effervescent tablets, certain cheeses, and dry powder mixes. On a UK ingredient label it appears as sodium bicarbonate, sodium carbonate, bicarbonate of soda, baking soda, or simply E500.