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 rennet is 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!

Reprinted from: The Art of Cheese

1 tablet = 1 teaspoon

Take a sharpie, write the date on the outside of the bottle when you first put into the frig!



I was recently making cheddar curds and decided to add a little color to one batch. Most of the time when I add Annatto, I’m following a recipe and don’t really think about the possible color outcomes. In looking on-line for how much to add, you might use recipe. However, even their “mild gold” color will give you striking results. The Stirred Curd recipe(p266) I like calls for 4 drops per gallon. I find that that will make cheese that is just shade off white.