What is rennet and how is it made?
Caglificio Clerici’s guide

What is rennet and where does it come from?

Animal rennet was discovered by chance about 7,000 years ago when people carried milk in pouches made from the stomachs of ruminants.

Rennet is a mixture obtained by extracting a complex set of enzymes from the fourth-stomach chamber (also known as the “abomasum”) of young nursing ruminants, such as calveslambskid goats and newborn buffaloes.

The naturally occurring enzymes it contains (especially chymosin, also known as rennin, and pepsin) are able to curdle the casein inside the milk, giving rise to a protein network commonly referred to as “curd”. This constitutes the first step in any kind of cheese production.

How do you make rennet at home?

First of all, we need to differentiate between the various kinds of rennet: while rennet paste can even be made at home, the production process for making powdered rennet or liquid rennet requires a checking system and production techniques that can only be carried out with professional equipment and cannot be replicated at home.

Rennet paste is what the Caglificio Clerici has always done best. It is extracted in a traditional manner, just like in olden times, from unweaned lambs and kid goats.

But how can you make it at home? Here are the instructions you need to follow for an excellent rennet paste made with your own hands:

  1. Get hold of the abomasum of an unweaned lamb or kid goat.
  2. Get rid of the fatty parts on either end.
  3. Sprinkle coarse salt on the abomasum while it is still fresh.
  4. Hang the abomasum to dry for a month in a dry room.
  5. Open it and remove unwanted contents (grass, hairs, soil, etc….), cleaning it as best you can without sacrificing too much coagulated milk.
  6. Rinse with water and drain. Add 10% of table salt and chop finely.
  7. Mix together, put the rennet into a jar and store in the fridge.
  8. If kept in the fridge properly, home-made rennet paste will last for about 1 year.

For a setting time of 15 minutes with goat’s milk, use roughly 3/4 grammes of rennet paste for every 5 litres of milk.

How is powdered rennet made?

As already pointed out, powdered and liquid rennet call for a series of industrial procedures which are difficult to replicate in a home environment.

By way of information, here are the various phases in the production process for powdered rennet:

  1. Collecting raw materials at -18°C and checking a series of parameters (physicochemical, microbiological)
  2. Extraction by cold maceration with an NaCI solution
  3. Recreation of the digestive process by enzymatic activation
  4. Purification and clarification (flocculation, filtration)
  5. Standardisation of parameters and checking physicochemical parameters
  6. Filtration of sterilising agent and checking microbiological parameters
  7. Slow enzymatic separation
  8. Mixing with standard-grain salt
  9. Slow-drying process in old traditional ovens
  10. Achievement of quality standards and parameter checking (physicochemical, microbiological)
  11. Packaging

An overview of Clerici products: Rennet for all requirements!

Liquid rennet

Clerici liquid rennet is suitable for a variety of purposes. The rennet is extracted from the fourth-stomach chamber of ruminants (calf, buffalo, lamb and kid goat), after which is it converted into liquid. Our vast product range means that you will always find the right rennet for your finished product, whether this be hard or soft cheese, cooked or uncooked, or fresh or aged cheese.

Liquid rennet is used for many different top-end cheeses including mozzarella, Taleggio, Grana Padano and Gorgonzola. It lends itself perfectly to each one and is fully compliant with PDO regulations.


Powdered rennet

Clerici’s powdered rennet has been a gold standard for over 100 years, staying ahead of the rest thanks to its consistency, performance and strength.

Grain size is standardised so as to avoid the creation of powder during the weighing phase, but also to ensure even enzymatic distribution on the grain surface which makes for consistent spoon dosage.

What is more, all Clerici’s powdered rennet is completely free from preservatives.


Rennet paste

Clerici’s rennet paste is based on time-honoured traditions. The lipase content establishes how piquant or pungent the finished product will be; it is expressed in Clerici Units (C.U.) which are a special unit of measurement developed in our laboratories.

As we can source rennet bags from specific geographical areas, we can also make single-origin rennet which complies with the strictest P.D.O. regulations.


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