Why does curd develop bubbles when stored in metal jars?

Question

Seeing bubbles in your curd that's stored in a metal jar? Learn what can cause this to happen and if the container material plays a role.

Answer 1

Curd develops bubbles in metal jars due to a chemical reaction between the lactic acid in the curd and the metal, producing hydrogen gas. This gas then forms the bubbles you observe.

Detailed Explanation:

Curd, also known as yogurt, contains lactic acid. When curd is stored in a metal jar, particularly if the metal is reactive (like aluminum or certain types of steel), the lactic acid can react with the metal. This reaction is a type of corrosion, where the acid slowly dissolves a tiny amount of the metal. A byproduct of this chemical reaction is hydrogen gas (H₂). Because the curd is a semi-solid, the hydrogen gas gets trapped within the curd's structure, forming small bubbles. The rate of bubble formation depends on the acidity of the curd, the type of metal, and the temperature. Warmer temperatures generally accelerate the reaction. The bubbles themselves are harmless, but the reaction can slightly alter the taste and texture of the curd over time.

Pro Tip:

To prevent bubble formation and potential changes in taste, store curd in glass or food-grade plastic containers. These materials are non-reactive and won't interact with the lactic acid in the curd.