Frequently Asked Questions

Questions about Rennet and other ingredients

Can I use the rennet past the expiry date?

Rennet loses activity over time, and will last until at least the best before date.  As it is getting to the end of its life, you will notice that it takes longer to set the milk. This is an indication that you should think about getting some more.  When it takes about 10 minutes longer than the time indicated on the recipe, you should get more rennet.  If you add extra rennet to make the cheese set in the required time, you may end up with bitterness developing in the cheese.  Provided that you haven’t contaminated the rennet in some way, the problem with keeping the rennet past the best before date is not one of danger from it being ‘off’ but because it is not setting in the correct time (or in some cases not setting at all), the characteristics of the cheese will be different.


What happens if I use too much rennet?

There is the risk that the cheese will go bitter as it matures.  This is not a health problem but a taste problem. 


What is the difference between rennet and junket tablets?

Junket contains the same enzyme as calf rennet. The difference is that junket often has a high pepsin content, which  means that when used in cheesemaking the cheese may develop bitterness. However, rennet is a more highly refined product with a higher chymosin content and lower pepsin content and as such, is less likely to develop a bitter flavour in cheese. Junket tablets are also a more expensive method of obtaining the same level of milk coagulation, in comparison with rennet.

Does rennet work the same as junket tablets?

Yes, rennet coagulates the milk the same way junket tablets did. It is just in a liquid form instead of a tablet form. Using the rennet rather than the junket tablets will also ensure your cheese does not end up tasting bitter (if used to the dosage rates on the bottle).


What does calcium solution do?

The calcium solution you ask about is added to homogenised milk to help produce a firmer set, and is also added to goat’s milk to produce a firmer set. The nature of goat’s milk means that it sometimes does not set as firmly as other milks, so calcium solution is recommended to achieve a more consistent set when making cheese from goat’s milk. (This is related to the fact that the calcium in goat’s milk is bonded to the protein, and therefore doesn’t set as well. When you add calcium solution, it is isolated as ‘ions’ in solution, and this makes a nice firm set). Note that it does not help with soft cheeses that are set by acidification, as these cheeses do not use rennet.