While all cheeses labeled Parmigiano-Reggiano definitely contain animal-derived rennet, Parmesan can go either way. In fact, Chad Galer, the vice president of food safety and product research at the Dairy Management Inc. estimates that more than 98% of rennet used in US-produced cheeses (including Parmesan) is from non-animal sources. (Animal rennet is, however, more commonly used in European cheeses.)
“We are definitely seeing more vegetarian rennet cheeses on the market these days,” says Julia Birnbaum, the Philly Cheese School founder, who chalks it up to a cultural trend towards plant-based eating. These non-animal derived rennets are typically cheaper for cheesemakers, adds cheese importer Adam Moskowtiz, and they make the final product kosher too.
How are vegetarian alternatives made?
The most commonly used form of rennet used across the world—featured in 90% of commercial cheeses—is fermentation-produced chymosin. This enzyme is genetically identical to the one found in the stomach linings of baby calves, but it’s more economical (small amounts can be used to make huge batches of cheese).
To make chymosin, scientists originally needed to extract the genetic code from a calf’s stomach cell. Since then, they’ve “been able to genetically modify fungi and bacteria to produce it,” says McNeil. After it’s made, “the chymosin enzyme is separated out from the mixture and purified, meaning that none of the genetically modified fungi DNA ends up in the final product.”
Other vegetarian rennets can be made from plants like stinging nettles, thistles, and fig trees, which is traditionally more popular in Spain and Portugal, says Birnbaum. Another option is mucor, Bailey tells me, which is a microbial fungus that releases enzymes to break down the protein in milk and give it “clotting power.” Though this one is a little finicky to work with. “Mucor has had a history of adding some not-so-nice qualities to cheeses, and the inconsistent results and sometimes unpleasant flavors can be costly and tricky for cheesemakers,” says Bailey.
Other styles of cheese are “acid set,” which means the curdling process happens with an everyday ingredient like lemon juice or vinegar. Because of that, these types of cheeses are often the easiest to make at home. Think: cream cheese, paneer, and ricotta.
Do vegetarian enzymes taste different from animal rennet?
While many take issue with the ethical considerations surrounding animal rennet—after all, it’s a byproduct of the veal industry—some experts argue it tastes better than these newer vegetarian alternatives.
In Moskowitz’s mind, “animal rennet fosters a wider, more complex flavor profile” than the microbial versions. Meanwhile, Birnbaum says she can’t taste a “huge difference” between lab made and calf-derived chymosin.
Bailey says, though it can be more fickle than chymosin, mucor makes for some “really delicious cheeses,” such as a new Fromage Frais from Grey Barn she’s obsessed with. And Birnbaum is a fan of various Spanish and Portuguese cheeses, such as Zimbro and Ovelha Amanteigado, that have always been made using thistle rennet. “These cheeses have a soft texture and a zippy, tangy flavor that reminds me of citrus,” she says.