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Rennet

Maureen Abood

Feb 19, 2013, Updated Jan 07, 2025

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Rennet is used to make cheese, ice cream, and other recipes and performs and imporant function in transforming dairy.

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All I can say to introduce rennet is if you have not cooked with it before, then great!, we are entering new territory together.

What is Rennet?

The easy definition of rennet is this: it’s a little tablet that is used to turn milk to cheese. Just as you have to inoculate milk with yogurt to make yogurt, you introduce rennet, an enzyme, into milk to encourage its proteins to coagulate and separate into curds and whey.

If we want to get into the history of it, rennet is wild and weird the same as yogurt. It reaches back to the olden days in the Middle East, when somehow a daring eater thought that the milk that had sloshed around in the stomach of an animal (the fourth stomach of an unweaned calf, to be precise) was appealing for a whole host of reasons (preservation had to top the list over imagined flavor for that first daring eater, but hunger is a strong impulse), then started using the enzymes from the animal stomach’s lining to coagulate and preserve milk themselves. Rennet’s complex set of enzyme leads to the formation of solid curds from the coagulating enzyme chymosin, which is crucial in the cheese production process.

The Different Types of Rennet

Vegetarian Liquid Rennet & Tablet Form Rennet: For convenience, liquid rennet is available, allowing cheesemakers to easily measure and incorporate it into their cheesemaking recipes. Additionally, rennet can be found in tablet form, making it easier for home cheesemakers to store and use in smaller amounts. The rennet primarily available is vegetarian. It’s made by Junket, which is a brand but it also refers to a custard dessert (or, even better, a press trip). The box in my mom’s kitchen cabinet in Michigan was so old-fashioned looking I assumed it had been in there since my childhood.

Animal-Derived Rennet: This is the traditional form of rennet obtained from calves. Its use is prevalent in many artisanal cheeses, including classic hard cheeses like Parmigiano Reggiano. While it results in a rich flavor, the use of animal-derived rennet has raised ethical concerns in the animal protection movement. Many cheesemakers explore alternatives.

Microbial Rennet: Derived from fungal sources, microbial rennet is becoming a popular choice among cheese makers, especially those in North America. Microbial coagulants are produced through fermentation, utilizing specific molds or bacteria to create enzymes that coagulate milk. This type of rennet is fine for vegetarians and is often labeled as vegetarian or microbial rennet.

Vegetable Rennet: This includes rennet extracted from plants like cardoon thistle and caper leaves. Vegetable rennet functions similarly to traditional animal rennet and is a good option for cheesemakers aiming to craft vegetarian-friendly cheese. The enzymes from these plants can help create different textures in soft cheeses and even cream cheese.

Fermentation-Produced Chymosin (FPC Rennet): This innovative rennet type involves genetic engineering to produce chymosin using yeast or bacteria. The process yields pure chymosin, making it a highly efficient and consistent coagulant for various cheeses. FPC rennet meets the demands for vegetarian cheese while maintaining the characteristics needed for quality cheese production.

The Cheesemaking Process

The cheesemaking process begins with the first step of milk preparation and heating, where temperature plays a crucial role in activating the proteolytic enzymes within the rennet. Once the milk is at the desired temperature, the appropriate amount of rennet is added to initiate the coagulation of milk. This step leads to the formation of a “clean break,” where the mixture separates into curds and liquid whey.

After curd formation, the cheese maker will cut the curds, allowing further whey to drain. Depending on the type of cheese being made—whether it’s fresh cheese, soft cheeses, or longer-aged cheeses—the process will vary. For our uses in making jibneh, there is some draining involved. For instance, in the production of hard cheeses, curds may be cooked further to expel moisture, enhancing the final product’s texture.

Where to buy Rennet

Rennet can be found online or at some larger grocery store chains.

The box looks exactly like the old-fashioned one my mom had on her shelf, so maybe hers wasn’t so old as I thought it was, after all. The yesteryear slogan on the recipe insert reads: Whether 6 months old or 6 feet tall, use Junket rennet tablets for them all.

Clearly this rennet, this Junket, is kind of strange. But I promise you that the Lebanese cheese we’re making is far from it. This cheese is pure white, mild, delicious, super-traditional, and I feel strongly you’re going to want to make it with some good milk and the rennet you pull of the shelf next time you’re at any old grocery store!