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Is rennet vegetarian? What is animal rennet? When making cheese, rennet usually isn’t optional. But, though they do the same thing, animal and vegetable rennet have very different beginnings.

What is Animal Rennet?

By its true definition, rennet is a combination of enzymes produced within the stomachs of young ruminants. Enzymes chymosin, pepsin, and lipase help the animals digest their mothers’ milk. Though rennet exists within stomachs of all ruminants, including goats and sheep, most cheesemaking rennet comes from young calves. It is a byproduct of veal production, and stomachs of older cattle produce less or no chymosin and can only be used for specific cheeses.

Rennet has been used for millennia in cheesemaking and was traditionally harvested by hydrating dried stomach pieces in whey or salt water, adding wine or vinegar to lower the pH, then filtering the solution. Modern rennet meets an enzyme-extracting solution then activates with acid before it’s filtered and concentrated then sold in liquid, powder, or tablet form.

What Does Rennet Do?

It’s said that, during ancient times, someone discovered rennet by using a butchered calf’s stomach to hold milk, later discovering the milk had soured and curdled, turning too a cheese product they could pick up with two fingers.

The protease enzyme chymosin coagulates milk proteins into curd. If you want to make cheese that isn’t soft and spreadable, you need rennet. It isn’t necessary for making ricotta cheese, but you will need to acquire rennet if you want to learn how to make mozzarella cheese.

Vegetarian Rennet: A Welcome Option

Because animal rennet cannot be harvested without butchering a calf, and because there were only so many calves to go around for so much cheese, vegetable rennet has been used since Roman times. Certain plant extracts also coagulate casein, such as nettles, thistles, and ivy. Vegetable rennet is suitable for lacto-vegetarians as well as those consuming kosher or halal diets. Available in liquid, powder, or tablet form, vegetable rennet has become the most widely used among home cheesemakers.

Other options include microbial or FPC (fermentation-produced chymosin) rennet. Microbial rennet is also vegetarian-friendly. FPC, created by isolating animal rennet genes and introducing them to microorganisms, is now the most commonly used commercial rennet because it is much less expensive. Wikipedia states that, by 2009, FPC was used for 80-90 percent of commercially made cheeses within the U.S. and Britain. The “vegetarian-friendly” nature of FPC is up to debate, but many vegetarians choose to avoid it because it originally came from an animal.

Finding Cheese with Vegetable Rennet

How do you know if your commercially produced cheese was made with animal or vegetable rennet or FPC? Reading labels may not help, as “enzymes” can come from any of the above. In fact, to be called Parmigiano-Reggiano, European Union law specifies that the cheese must contain raw cow’s milk, salt, and calf rennet (Council Regulation [EC] No 510/2006 ‘Parmigiano Reggiano’ 3.3). Vegetarian Times recommends developing a relationship with a local cheesemonger or shopping at Whole Foods or Trader Joes, both of which list rennet sources in their store-brand or generic cheeses. Also look for organic cheeses, since many organic cheesemakers prohibit products from cattle living in feedlots and may avoid animal rennet altogether as a failsafe.

Another way to ensure your cheese is vegetarian-friendly, kosher, or halal, is to create it yourself by ordering vegetable rennet online or at local brewery or cheesemaking supply stores.

Where to Buy Rennet for Cheesemaking

New England Cheesemaking Supply Company, which provides almost all the cheesemaking supplies you will need (with the exception of the milk), sells both animal and vegetable rennet in liquid, tablet, and powdered forms. One bottle of liquid will coagulate up to 90 gallons. Their animal rennet is 90% chymosin (calf) while their vegetable rennet comes from the mold Mucur Miehei. And, according to their website Cheesemaking.com, which rennet you use is a matter of personal preference.

Rennets are standardized so all choices work the same to coagulate milk. Animal rennet is better for longer-aged cheeses, claims the website’s FAQ section, because residual components in the rennet help complete the breakdown of proteins in the cheese. Vegetable rennet may leave a bitter taste after six months of aging, but their product is kosher and repackaged under kosher supervision. Vegetable rennet is also often sold double-strength, so you use half as much even when bottles are the same price per volume. Liquids are easier to dilute and use in cheesemaking, since tablets may never fully dissolve, but tablets allow you to purchase less and keep it frozen if you don’t intend to make 90 gallons worth of cheese within the standard shelf life. Powdered rennet is best for large batches while liquid and tablets measure well for home cheesemaking.

Liquid animal rennet lasts up to one year if refrigerated, and liquid vegetable rennet lasts 4-6 months under the same conditions. Organic vegetable rennet may only last 3-4 months. Tablets should be frozen for the best shelf life and can remain good at least five years; without cold storage, do not expect it to be effective past one year. Store powdered rennet in the refrigerator, away from direct light. After expected shelf life, rennet strength declines.

Are There Other Rennet Substitutes?

If you make cheese, use cheesemaking rennet. Junket, which is marketed for desserts like custards and ice creams, is not strong enough for cheese. And, though some hardcore cheesemakers choose to extract their own calf rennet using traditional methods, or make vegetable rennet from figs, Cheesemaking.com warns that using homemade rennet may mean you are unable to sell your product under local laws.

Another precaution for rennet: to keep it shelf-stable, it often contains preservatives which may trigger intolerances such as corn allergies. Some liquid rennet contains propylene glycol.

If you want to avoid all rennet in cheese, create soft products such as ricotta, paneer, labneh, and cream cheese. Use lemon juice instead of vinegar with the ricotta and paneer, if you are allergic to corn. Rely solely on cultures used for making cheese at home, and straining, to thicken labneh and cream cheese.

Do you prefer vegetable rennet, animal rennet, or would you rather craft cheeses using no rennet at all? Let us know why so other cheesemakers can learn, as well.