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Rennet is one of the most fascinating elements of cheese making.  It is often portrayed as a magical chemical which turns milk from a liquid into a solid, but the reality is it’s actually a very natural process.

When a calf suckles milk from it’s mother, the milk it ingests is solidified by enzymes in it’s 4th stomach, allowing the milk to be retained in the stomach long enough for digestion to occur.

Where rennet comes from

Where rennet comes from

The story goes that rennet was originally discovered by accident, when travelers used stomach linings as canteens to transport milk, and noticed that with sufficient temperature, the milk would turn solid.

Wikipedia describes rennet as follows:

Natural calf rennet is extracted from the inner mucosa of the fourth stomach chamber (the abomasum) of slaughtered young, unweaned calves.

Over the years, this process has been refined to use only the required enzymes in the stomach to coagulate the milk, but the process has remained the same.  Recently, there has been a focus towards vegetarian rennet, either from natural sources (nettles, or any other weak acid), or artificially created in a laboratory.  Even those cheese makers who still use animal rennet have mostly switched to generic animal rennet, rather than using extracts from a specific animal.

THE EXPERIMENT

Following on from my experiments into milk type, salt type and rennet quantity, I thought it would be interesting to perform an experiment to compare different types of rennet.  My aim is to find whether there is a discernible difference in the cheese produced in terms of yield, texture and flavour.

Each rennet was kindly provided by Jaap of Jongia, who also runs the excellent Cheese Making Shop, and has this to say:

Rennet is not a chemical, it is an ingredient

The types of rennet I used were as follows:

1. Vegetarian Rennet (available here)

Vegetarian rennet

Vegetarian rennet

This rennet is microbial, although some vegetarian rennets are genetically engineered.  There are some interesting notes on microbial rennet on BioRen’s site,  although they are heavily biased, since they produce animal rennet.

2. Generic Animal Rennet (available here)

Generic animal rennet

Generic animal rennet

Generic animal rennet generally comes calves, although may contain other animal extracts.  It’s termed as “Super Industrial Strength”, although the dosage instructions are similar to the other rennets in the experiment.

3. Premium Animal Rennet

Premium natural animal rennet

Premium natural animal rennet

Available from BioRen, this rennet is produced exclusively from the stomachs of young calves, and extracted into liquid form.

4. Calf Rennet Paste (liquid form available here)

Calf rennet paste

Calf rennet paste

Another rennet from BioRen, it should naturally be more adept at coagulating cow’s milk, with the description citing “spicier and tastier maturation flavours”.  The paste form makes it slightly more tricky to work with than liquid rennet due to the difficulty of getting it into a syringe.

5. Lamb Rennet Paste (available here)

Lamb rennet paste

Lamb rennet paste

From BioRen again, termed “Semi-Piccante” it’s said to give a spicier flavour than normal rennet when used with ewe or even cow cheese.

6. Kid Rennet Paste (available here)

Kid rennet paste

Kid rennet paste

The final rennet from BioRen, said to impart a typical goat cheese flavour to all types of milk.

So that’s the background, now on with the cheese making!

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