What does rennet mean?
Rennet is an enzyme preparation or, more specifically, the enzyme rennin, used to coagulate milk during cheesemaking. Traditionally, rennet was obtained from the stomach of a calf, where the enzyme occurs naturally. When added to milk in the right conditions, it causes the milk proteins to form a network that traps fat and other components, producing a curd that can be cut, drained, and aged into cheese. The term can therefore refer either to the commercial preparation used by cheesemakers or to the active biochemical substance within it. Although now often replaced by microbial or vegetable alternatives, rennet remains important in the history and terminology of cheese production. It is also notable for illustrating how a biological catalyst can transform an ordinary liquid into a structured food. In precise biochemical contexts, rennin distinguishes the individual enzyme from the broader preparation.
nounAn enzyme-containing preparation, traditionally obtained from the stomach of a calf, used to coagulate milk in cheese-making. The term may also refer specifically to the active enzyme rennin.
- An enzyme-containing preparation, traditionally obtained from the stomach of a calf, used to coagulate milk in cheese-making.
- The enzyme rennin itself, especially when discussing its biochemical action.
"The cheesemaker added a little rennet to the milk so that it would begin to coagulate."
"The cheese was set with rennet before the curds were cut and drained."
"Scientists studied how rennet coagulates the proteins in milk."
The plural is grammatically possible but uncommon; rennet is usually used as a mass noun referring to an enzyme preparation or enzyme.
"The laboratory compared several rennets under identical conditions."
Rennet is the tiny enzyme behind a giant transformation: milk becoming cheese.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does rennet come from?
The English word entered use in the early 17th century, borrowed from Old French rennet, a term for a substance that curdles milk. Old French rennet is generally connected with rennir, meaning “to curdle” or “to coagulate,” although the deeper origin of that word is uncertain. In modern usage, the related biochemical term rennin names the specific enzyme associated with milk coagulation.
Related word forms
How rennet is actually used
Rennet is primarily a food-science and cheesemaking term. In general discussion it usually refers to the preparation, while technical biochemical writing may use it for the enzyme itself; the more precise term in that context is rennin.
Easily confused with rennet
Rennet commonly names the enzyme-containing preparation used in cheesemaking, while rennin is the specific proteolytic enzyme responsible for coagulating milk.