International Board of Certified Lactation Consultant (IBCLC) Practice Exam

Which component of milk protein forms curds?

1. Whey

2. Casein

3. Serrum

4. Globulin

The correct answer is: Casein

The correct choice relates to casein, which is the primary milk protein known for its ability to form curds. Casein proteins comprise about 80% of the total protein content in cow's milk and around 20-45% in human milk, depending on the stage of lactation. This structure allows casein to precipitate into curds, especially in acidic conditions, such as during digestion in the stomach. Curdling is an essential process that aids in the digestion and absorption of nutrients. Casein forms a gel-like substance when it interacts with acid or rennin, which later slows down digestion and provides a sustained release of amino acids into the bloodstream. This property is particularly beneficial for infants, allowing them to efficiently process and absorb nutrients. This biochemical characteristic of casein is a vital aspect of lactation and nutrition, particularly in understanding how different milk types support infant growth and development. In contrast, whey proteins, although present in milk, remain soluble and do not form curds in the same way that casein does.