AP BIOLOGY

Detailed explanation-1: -rennin, also called chymosin, protein-digesting enzyme that curdles milk by transforming caseinogen into insoluble casein; it is found only in the fourth stomach of cud-chewing animals, such as cows.

Detailed explanation-2: -In the presence of calcium rennin changes irreversibly the casein of milk to a paracasein which is then acted upon by pepsin. This enzyme is said to be absent from the stomach of adults.”

Detailed explanation-3: -The shepherds found that the milk, which had been placed in the stomach in the morning, had curdled and formed cheese by noon. (Curdling occurs when the milk becomes thicker and somewhat lumpy.) Today, it is known that the curdling is due to the presence of an enzyme, rennin, in the animal’s stomach.

Detailed explanation-4: -Coagulation can happen in two ways: as an enzymatic reaction (rennet) or as a product of acidification (adding acid). “Ricotta is a simple example of a cheese coagulated using acid-lemon juice or vinegar, depending on the recipe, ” says Elena Santogade, author of The Beginner’s Guide to Cheese Making.