Why does milk curdle when it is mixed with vinegar?
Credit: Dual Dual Getty Images
Q:

Why does milk curdle when it is mixed with vinegar?

A:

Quick Answer

Milk curdles when mixed with vinegar because the acid from the vinegar causes the protein molecules in milk to come together to form visible solids.The solids float in the clear whey, forming curdled milk.

  Know More

Full Answer

Milk primarily consists of protein, sugar and fat. Normally, the protein molecules in milk repel each other and they float separately in whey. Adding an acid, such as vinegar, increases the number of positively charged hydrogen molecules in the solution. These hydrogen molecules bind to the protein molecules, causing them to attract other protein molecules. When the protein molecules bind, they form curds, which float in the liquid whey.

Adding vinegar to milk is common in preparing cheese. Cheese recipes require warming the milk because curdling happens faster at warmer temperatures. When adding vinegar to milk to make a buttermilk substitute, however, using cold milk causes the milk to thicken and have a slightly acidic quality without fully curdling and separating the curds from the whey.

Milk curdles when its acidity increases for any reason. Thus, spoiled milk also curdles. This is because the metabolic processes that bacteria in milk undergo release lactic acid, and lactic acid increases the acidity of the milk, causing curd formation. Lemon juice also causes milk to curdle.

Learn more about Food Facts

Related Questions

  • Q:

    Why does cereal get soggy in milk?

    A:

    The atoms in milk move more quickly than the atoms in cereal, because liquids have faster atomic movement than solids, and the smashing of the milk atoms against the cereal atoms leads to diffusion. Diffusion is a scientific term for the breaking down of a solid.

    Full Answer >
    Filed Under:
  • Q:

    Is vinegar an acid?

    A:

    Vinegar is acidic and contains acetic acid. The pH of vinegar varies by type. Distilled white vinegar can have a pH as low as 2.4, while palm vinegar has a pH between 5 and 6.

    Full Answer >
    Filed Under:
  • Q:

    Where does vinegar come from ?

    A:

    Vinegar is created through the fermentation of ethanol by acetic acid bacteria. When a slow fermentation method is used, the process takes anywhere from two months to a year. With a quick fermentation process, typically used for commercial vinegars, a bacterial culture called "mother of vinegar" is added to the ethanol liquid, and then air is added. Vinegar can be made this way in as little as 20 hours.

    Full Answer >
    Filed Under:
  • Q:

    Why does milk curdle when acid is added?

    A:

    The positively charged particles in acid break apart the groups of negatively charged proteins in milk, forming clumps. Caseins are largely the type of proteins found in milk.

    Full Answer >
    Filed Under:

Explore