Sheep Milk Cheese. Organic produce for sale at market.

In its way, cheese is just as subtle and as variable as wine. One major difference is that, unlike wine, home hobbyists can produce truly outstanding cheeses with very little in the way of specialized equipment or supplies. One ingredient you’ll usually need to order is rennet, which helps the cheese curdle, but you can easily make your own DIY vegetable rennet.

The Case for Vegetarian Rennet

Traditionally, cheeses have been made by making milk coagulate, or curdle, with the addition of a small piece of stomach from a calf or lamb. The stomach contains an enzyme called _chymosi_n that helps the casein protein molecules bind together, forming a firm curd that can be compressed to make a sliceable, age-able cheese. That enzyme is the active ingredient in rennet.

That’s all well and good if you have ready access to immature livestock and don’t mind sacrificing one now and then to the cheese-making process. The problem, whether you’re a modern homesteader or an ancient Roman peasant, is that you may not have an animal to spare – or any at all – so DIY cheese requires a substitute.

Modern industrial cheese making uses a genetically modified yeast to produce the enzyme in bulk quantities, but that’s not an option for home-scale producers. Instead, you can use one of the many plants that contain similar enzymes. The two most common and easily foraged options are nettles and thistles.

Homemade Rennet From Nettles

If you’re “blessed” with a large patch of nettles somewhere in your neighborhood, you can easily gather enough for rennet-making. A pound of fresh leaves will make enough homemade rennet for 2 gallons of milk. Rinse the leaves thoroughly under cold water; then add them to a pot with 2 cups of water.

Bring the pot to the verge of boiling; then cover it and let the leaves simmer for 30 minutes. Once the leaves are ready, add 1/2 tablespoon of sea salt to the mixture – this helps break down the leaves and extract the enzyme – and stir it until it’s dissolved. Line a colander with cheesecloth, and set it inside a clean bowl. Pour the nettle soup through the cheesecloth, and let it drain until it stops dripping.

Use half of this infusion, about 1 cup, per gallon of milk. Until you’re ready to make the cheese, keep your rennet tightly covered in a non-transparent container. The enzyme doesn’t do well when exposed to light.

Homemade Rennet From Thistles

You can gather nettles at any time of the year, but if you choose to make your vegetarian rennet from thistles, you’ll need to wait until they’re blooming. Watch them closely; you’ll want to harvest the blossoms once the fresh green of the flower heads starts to fade, but before they go to seed and turn to fluff.

Dry the flower heads thoroughly on a sunny windowsill or in a dehydrator if you’ve got one, until they’re completely dry. Next, separate the pretty purple stamens from the rest of the dried thistle. That’s the part that contains the enzyme. To use them, grind the stamens in a clean spice grinder or a mortar and pestle. You need approximately 4 grams of this powder to set a gallon of milk, but most people don’t have an accurate-enough scale in their kitchen to weigh it properly. Five tablespoons of powder should weigh 8 to 10 grams, enough for 2 gallons of milk.

Soak the powder in 1/2 cup of warm water for 10 minutes. Strain the muddy-looking liquid to remove the thistle residue, and what’s left is your rennet. Use half this amount for each gallon of milk in your recipe.

Making Cheese With Your Vegetable Rennet

The cheeses you make with your vegetable rennet won’t be quite like regular rennet cheese. Cheeses made with thistle rennet tend to be soft rather than firm, and become positively runny – like a ripened Brie – as they age. Nettle rennet makes a firmer curd, but it’s salty so you’ll need to reduce the amount of salt in your recipe to compensate for that.

Both types of vegetable rennet give the finished cheese a faintly bitter tang. It goes well with the natural funk of sheep’s and goat’s milk, and some traditional European cheeses work that combination. It’s less suited for use with milder cow’s milk, but you can experiment by adding bacterial cultures to your milk to “funk it up” and help it stand up to the rennet, or just fall back on add-ins like fresh herbs and spices. The bitter flavor will intensify over time, so cheeses made with vegetable rennet should be eaten within the first couple of months.