Rennet: the quiet rock star of cheesemaking

Most people don't know much about rennet. In the world of cheese, rennet is like the quiet member of the band who gets the group together and then lets others take the spotlight. It doesn't demand attention – it just calmly goes about its work. But without rennet, mozzarella would just be milk, colby would just be cream, and limburger would just be a warm glass of lactose.

You see, it's rennet that starts the whole cheesemaking process off by separating the liquid whey from the solid curds that will go on to become a chunk of cheddar, a slice of swiss, or a block of butterkäse.

Here in Wisconsin, we understand that rennet is responsible for pretty much everything we hold dear in this life, cheese-wise. So, we're working hard to make sure rennet gets to take its bows with the rest of the cheese crew.

Take a spin around our website to discover all the amazing rennet cheese made right here in Wisconsin. Check out our recipes for ideas for delicious dinners or sumptuous snacks made with Wisconsin Cheese. Or read on for the 411 on rennet's role in the cheesemaking process.

The rennet rundown

Not sure what rennet is, what it does, or why you should care? Well, if you care about cheese at all, you should take an interest in rennet.

Rennet is a set of enzymes that traditionally were found in and harvested from the stomachs of ruminant animals like cows, sheep, and goats.

To make cheese, cheesemakers add rennet to milk to curdle it, separating the solid curd from the watery whey. The curd becomes the building block that cheesemakers use to create all kinds of cheeses.

Historians speculate that the coagulating power of rennet was likely discovered when humans long ago tried transporting milk inside a container made from the stomach of a calf or lamb, only to discover at the journey's end that the milk had been transformed into curds and whey.

Today, there are several different types of rennet used in the cheesemaking process.

  • Animal rennet is still one of the most common types. Animal rennet is a byproduct of the meat butchering process.
  • Vegetable rennet is made with enzymes from plants that have coagulant properties – fig leaves, melons, safflower, and wild thistle are some of the common sources.
  • Microbial rennet uses fermented enzymes from fungi or bacteria. But as this type of rennet can leave the cheese with a bitter flavor, it's usually only used in cheeses that are not aged for a longer period of time.
  • Fermentation-produced chymosin is a genetically engineered rennet that is based on the genes from a ruminant animal's DNA.

Cheesemakers may choose to work with liquid rennet which is easy to measure, with rennet in a tablet form that has a longer shelf life, or with powdered rennet which is both easy to measure and can be stored for longer periods of time.

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FAQs: What is rennet?

What is rennet?

Rennet is the product used in cheesemaking that coagulates the milk and helps to separate the solid curd from liquid whey. Traditionally, rennet was extracted from the lining of the fourth stomach of young calves and other ruminant animals. Today, however, rennet also refers to a variety of substances made from plants, microbes, or genetically engineered substances that have the same coagulating properties as animal rennet.

How does rennet work?

Rennet contains an enzyme, chymosin, that encourages the casein protein particles in milk to clump together, forming the curd and trapping fats and minerals while releasing moisture, or whey.

Is all cheese made with rennet?

No. Certain soft cheeses – including cream cheese, ricotta, quark, and paneer – are made without rennet. Most cheese, however, uses some form of rennet derived from animals, plants, microbes, or other sources.

Rennet rules in Wisconsin

Here in Wisconsin, we know that rennet is the unsung hero of the cheesemaking process. We understand that without rennet there would be no romano, gruyère, or cheddar, so we're always ready to give rennet the recognition it deserves.

That's because we take cheese pretty seriously in Wisconsin. Our cheesemakers have been perfecting their craft for 180 years, since before we were even a state. Today, we make more flavors, varieties, and styles of cheese than anywhere else on earth, and our cheesemakers bring home more awards than any other state or country. That's what happens when a whole state is focused on one thing – making the tastiest, highest-quality cheese in the world.

So, next time you're shopping for cheese, just make sure that chunk in your hand has a Proudly Wisconsin Cheese badge on the label. That's when you know you'll be sampling some of rennet's best work.

Craving award-winning aged cheddar, pining for parmesan, or searching for a new cheese to try? The world’s best cheese is just a click away! Explore our directory of Wisconsin cheesemakers and retailers who offer online cheese shopping and get cheese shipped right to your door. What are you waiting for?

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