Rennet for Cheese Making

Rennet for Cheese Making

Rennet is a coagulating enzyme used in cheesemaking to turn liquid milk into a firm curd. It works by breaking down kappa-casein, allowing milk proteins to clump together and form a solid mass.

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⭐ Types of Rennet

1. Animal Rennet (Traditional)

• Made from the abomasum (fourth stomach) of young calves, lambs, or kids.

• Contains the enzyme chymosin.

• Best for aged cheeses because it produces a stronger curd and better flavor development.

• Common in: Parmesan, Cheddar, Manchego, Gouda.

Pros: Excellent flavor; very reliable
Cons: Not vegetarian; may be hard to source locally

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2. Vegetable Rennet (Plant-Based)

• Derived from plants like thistle, nettle, artichoke, fig sap, or cardoon.

• Traditionally used in Mediterranean cheeses.

Pros: Vegetarian-friendly, natural
Cons: Can cause bitterness in aged cheeses; best for fresh or young cheeses

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3. Microbial Rennet

• Produced by fungi (like Rhizomucor miehei).

• Often labeled as “vegetarian rennet”.

• Very common in commercial cheese production.

Pros: Inexpensive; vegetarian
Cons: Can create bitterness if the cheese is aged a long time

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4. FPC Rennet (Fermentation-Produced Chymosin)

• The most consistent rennet used worldwide.

• Created through fermentation using genetically modified bacteria or fungi.

• Chemically identical to natural chymosin.

Pros: Very predictable, clean flavor, preferred by many artisan cheesemakers
Cons: Not considered “traditional” by some

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⭐ Forms of Rennet

✔ Liquid Rennet

• Most common and easiest to measure.

• Widely used for all cheese types.

✔ Tablet Rennet

• Long shelf life, portable.

• Must be dissolved before use.

✔ Powdered Rennet

• Highly concentrated.

• Used more by commercial cheesemakers.

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🧊 How to Store Rennet

• Refrigerate after opening.

• Liquids: good for ~1 year.

• Tablets/powders: store in a cool, dry place, last several years.

• Avoid heat, air, and light.

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🥛 How Much Rennet to Use

General rule (liquid rennet):

• ¼ teaspoon per 4 liters (1 gallon) of milk

• Always dilute in non-chlorinated water (distilled or filtered).

Note: Different brands vary—check your bottle.

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🧀 Best Rennet for Different Cheeses

Cheese Type	Recommended Rennet
Mozzarella	Liquid animal or FPC
Cheddar	Animal or FPC
Parmesan	Animal rennet
Brie/Camembert	Liquid animal rennet
Feta	Animal or microbial
Paneer/Ricotta	No rennet needed
Fresh cheeses (queso fresco, farmer's cheese)	Any rennet works

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🛒 Where to Buy Rennet (General Options)

• Cheesemaking supply stores

• Homebrewing shops

• Online retailers (Amazon, New England Cheesemaking Supply, etc.)

• Some specialty grocery stores

OTHER SOURCES

What is rennet?

Traditional animal rennet is an enzyme derived from the stomachs of calves, lambs or goats before they consume anything but milk. (Ours is all from calves.) It is about 90% pure chymosin. 

Vegetable rennet is obtained from a type of mold (Mucur Miehei). However, even though it is derived from mold, there is no mold contained in the final product. It is an equivalent chymosin product which works equally well but is not animal derived. 

We have recently added organic vegetable rennet to our catalog. Rennet thrives at temperatures in the 85-105F range, but it won't be deactivated completely until it reaches the 140F's. Rennet continues working to set the milk as long as it has the right conditions. So, when a recipe calls for cutting the curds after a certain time period, it is important to follow the directions. Otherwise, your curds may be too firm for the cheese you are trying to make.

How do I choose which rennet to use?

Rennet is standardized, so all the different kinds of rennet (liquid, tablet or powder) work the same to set milk. Liquid is the easiest to work with because you can measure it very precisely. However, the powders and tablets will keep better under more adverse conditions. 

Calf rennet is considered to be the best choice for longer aged cheeses because some of its residual components help to complete the breakdown of proteins. Some of the more complex proteins in the vegetable rennet can have a slightly bitter taste after 6 months of aging. The liquid vegetable rennet is Kosher, but it has been re-packaged without Kosher supervision.

How much salt is in rennet?

The amount of salt in rennet is miniscule. It is there as a preservative. Considering that you add 1/4 teaspoon of rennet to a gallon of milk and that much of the rennet runs off with the whey during draining, the amount of salt left in the cheese is virtually impossible to measure. 

If you are interested in making cheese with no salt, the fresh cheeses, Mozzarella and Ricotta are best suited for this. The aged cheeses require a slight amount of salt to sow bacterial activity.

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