Rennet: Types, Techniques & Testing

Rennet: Types, Techniques & Testing

Rennet is the coagulant that is used to set a curd when making cheese.   Traditionally rennet is made from an enzyme found in the stomachs of baby calves, goats or lambs. Vegetable rennets are obtained from a type of mold, and there are also plant-based rennets such Thistle rennet.   Rennet comes in tablet, liquid and powder form.

To use your rennet, you first must dilute the desired amount in non-chlorinated water (we use distilled water but if you have a good filter on your water source, that will generally take all the chlorine out of the water). If using rennet tablets, just be aware that 1 tablet = 1 teaspoon and when you dilute it in the water it won’t actually dissolve. Use your diluted rennet within 30 minutes or it will lose its effectiveness.

Rennet has a limited shelf life – liquid rennet lasts for 7-8 months when refrigerated and tablets last for up to 2 years when stored in the freezer. If you are unsure how old your rennet is or whether or not it is still effective, you can do the following test:

  • Heat one cup of milk to 90F.
  • Dilute ¼ tablet or ¼ tsp liquid rennet in ½ cup non-chlorinated water.
  • Take 2 tsp of the diluted rennet and add it to the milk.
  • Stir gently for 30 seconds.
  • If the rennet is working, the milk surface will form a slight film in 2 minutes and will have formed a firm curd within 6 minutes.

If not, it might be time to get some new rennet!


Submitted by Kate Johnson

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