Enzyme, not product category
It helps to separate two words that get used interchangeably. Rennet is what you buy — a coagulating preparation. Chymosin is the enzyme that does most of the clotting work inside it.
How it acts
Chymosin cleaves kappa-casein at a specific point. Removing that stabilising fragment strips the micelles of what keeps them apart, and in the presence of calcium they begin to aggregate into a gel.
Chymosin's value to cheesemakers is that specificity: it does its cutting where it should and comparatively little elsewhere, which is one reason it is favoured where the cheese will be held or aged.
Where you meet it
- In traditional animal rennet, as the dominant clotting enzyme.
- In coagulants produced by fermentation, where chymosin is the clotting enzyme supplied.
Coagulation is never controlled by one variable. Milk composition, temperature, pH, calcium, the cheese style and your process conditions all shape how the curd forms — the coagulant is one input among several.
Frequently asked
Is chymosin the same thing as rennin?
Rennin is an older name for chymosin. They refer to the same enzyme.
About the author
Bixa Products — Editorial team
Educational content written by the Bixa Products team, a family-owned cheesemaking ingredient company specializing in rennet and chymosin. Technical guidance is written conservatively: where a value depends on your milk, process or product, we say so instead of guessing for you.
- Family-owned cheesemaking ingredient company
- 30+ years in the Latin American cheesemaking market
- Specialists in rennet, chymosin and milk coagulation