How It Works

Bacteria causes milk to curdle


It’s the worst way to start the day when you unknowingl­y pour the coagulated lumps of gone-off milk into a freshly brewed tea. Milk is predominan­tly made up of proteins, sugars and fat, but it’s the proteins that give the milk its colour and texture. In fresh milk these protein molecules repel one another, almost in the same way the matching poles of two magnets would. However, when the ph of the milk is lowered, the protein molecules begin to attract one another and clump together. This happens when the naturally occurring bacteria within the milk begin to multiply and feast on the milk’s sugar content, releasing acids that lower the milk’s ph. This build-up of acid also results in the sour taste some of us may have unwittingl­y experience­d when drinking from the bottle.

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