Homemade Cheese Science (2) – Rennet & fresh herb cheese

Being a food scientist I have quite a bit of theoretical background in the (food) sciences. But nothing’s better than actually applying that science. Which is also the great thing about food science: it can be applied in a kitchen very easily without a lot of fancy ingredients!

After having made cheese myself once, it was time for a next ‘experiment’. Last time I made an Indian style cheese, paneer. This time I would use a different recipe and method, making a fresh herb cheese.

Making Cheese

In a previous post I’ve digged into the details of the cheese making process, walking through the most important steps. But since I like applying the theoretical knowledge I had to make cheeses as well of course. The paneer was my first cheese making experiment, this fresh herb cheese my second. It’s not only ‘herby’, it’s also made with an enzyme instead of an acid, hence the rennet in the post title!

Cheese making kit

It was thanks to a kit I bought at a nice discount in the sales isle in our supermarket that I made a ‘rennet cheese’. The kit I bought was one from Boska. It contained the rennet that I needed (which actually was the only reason I bought the kit), but other than that it had quite a strange selection of items. In there was a lot of salt and herbs, which I would say most people have in their homes. But a cheescloth or little press weren’t in there, which I assume most people don’t have.

Luckily, I had a cheesecloth after my previous attempt to make the paneer. And my hands served as a pretty decent press.

cheese-making-kit-boska
The Boska cheese making kit. The main reason I decided to buy the kit were the rennet tablets since those cannot be bought in most stores. The thermometer is nice to have, but not very practical since it would drop down in my pan, so I used my own digital thermometer (IKEA).

Making cheese

When making cheese, one of the most important steps is curdling the milk. During this step part of the proteins form large structures resulting into soft curds which float around in the remaining liquid. It’s these curds that make the final cheese.

Milk curdles when the activity of the κ-casein is somehow stopped. This protein normally prevents the proteins from curdling. The curdling of the cheese can be induced in two ways:

  1. Add an acid
  2. Add an enzyme

Read more in the post dedicated on the cheese making process.

The enzyme that curdles

It’s the enzyme that I’ll be using today for making my cheese. The enzymes cannot be found in most supermarkets, you’ll have to go to a speciality store.

Introducing rennet

But before we rush into that, let’s take one step back. How does this enzyme work, and what is it? The enzyme that curdles the milk is called chymosin and it can be found in rennet. Rennet is made in the stomachs of various young animals. It is a mixture that contains various enzymes. Originally rennet came mostly from veal stomachs. Nowadays though the enzyme can be made in other ways. Mixtures of enzymes that cause cheese to curdle are still called rennet, even if they aren’t the original veal’s mixture.

Enzymes are catalysts

As you might remember, an enzyme is a protein, a special type of protein. Enzymes can catalyse chemical reactions. This means that they can help chemical reactions along, without actually being used up themselves.

In the case of cheese and chymosin, the chymosin cuts up the κ-casein. This ‘deactivates’ the protein, and thus: the curdling of cheese is started!

curdling-milk-with-rennet

Choosing between acid and enzyme

With both the acid and the enzyme cheese can be made. They can be used individually, but a lot of recipes also cal for both. Ratios might differ as do concentrations. Both should be treated in a different way to make a good cheese, but if processed correctly can also be used simultaneously.

Enzymes denature when heated too much (often already at temperatures >40-50C). When making a cheese with enzymes the milk shouldn’t be hot when adding the enzyme, this will deactivate the enzyme. Once the milk has curdled, the milk can be heated again, the enzyme has done its job so can be deactivated (but doesn’t have to be).

On the other hand, acids works faster at a higher temperature! So you will see higher temperatures being used (as was the case with the paneer recipe).

There are differences in taste and flavour between using the two. For instance, using an acid will make the cheese slightly more acidic (less sweet), whereas the enzyme is more neutral. Apart from that, they can result in different textures, but I haven’t made enough cheese yet to be a good judge of that.

Fresh Herb Cheese Recipe

Now that we’ve discuss the theory, it’s time to get working/experimenting! Here’s the recipe for my fresh herb cheese, using rennet.

Homemade Cheese Science (2) - Using rennet in fresh herb cheese
Author:
Ingredients
  • 1l of fresh full fat milk
  • ½ rennet tablet (but the dosing will depend on the tablets you've got, follow the instructions)
  • 20ml of buttermilk
Instructions
  1. Heat up the fresh milk to 30C.
  2. Mix the rennet with a little bit of water to dissolve it. Pour the rennet solution in the warm milk and through through well.
  3. Leave on the stove for at least 1 hour, maintaining it at 30C.
  4. It is important the milk is any hotter when the rennet is added, nor is heated a lot more in between. This will cause denaturation of the enzyme chymosin, making it inaffective.
  5. Pour off the whey.
  6. Mix in salt and herbs as desired.
  7. Place the curds that have formed in little cheese moulds inside a cheese cloth. Press the curds down to push out more water. Leave to rest for a while.
  8. Voila, your cheese is good to go!

Sources

Some of the sources I used: Colorado State University, Wikipedia.

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