Have you ever heard the story of an Arab nomad who accidentally invented cheese? Legend has it that while traveling through the desert, he stored milk in a bag made from an animal's stomach. After a long, hot journey, he opened the bag to find the milk had curdled, and—voilà!—the first cheese was born. Whether this tale is true or not, it reveals an important fact: rennet, found in the stomach lining of young ruminants (cud-chewing animals), is key to transforming milk into cheese.
Rennet contains enzymes that help curdle and thicken milk, making it easier for baby animals to digest. For cheesemakers, adding a small amount of rennet to milk causes it to form curds (the solid part) and whey (the liquid part). Those curds eventually become the delicious cheese we know and love, while whey has its own uses—but more on that in another article.
For centuries, animal-derived rennet was the only option, and it remains a popular choice, especially in Europe, where it’s still used in many firm, aged cheeses. Animal rennet, in particular, has historically been considered best for aging cheeses due to its reliable performance in the process.
But cheesemaking has evolved! Today, many cheesemakers use vegetarian alternatives made from microbial or yeast-based coagulants. There’s even a rare but fascinating plant-based option: coagulants derived from thistle, such as cardoon, though these are less common.
And, of course, some cheeses—usually fresh ones—skip the rennet altogether. Instead, they rely on acidification alone to achieve that delightful curdling effect.
Curious about which cheeses use which type of rennet? You can explore the options using the new filters in California’s first and only Cheese Directory on our website. It’s a fantastic resource for cheese lovers who want to dig deeper into the world of artisan cheeses.
