Coagulant Test

The following procedure is one way to easily test the strength of your coagulant or rennet if you suspect that yours may be losing strength. This test, which checks clotting ability, is commonly known as a flocculation test. Please read the entire procedure before beginning.


You will need:

Measuring spoons

Measuring cups

1/4 cup milk

2 x 1/4 cups cool non-chlorinated water

Method to heat your milk

Transparent cup or glass

1/4 - 1/2 tsp of the suspect coagulant or rennet

1/4 tsp. calcium chloride if using store-bought milk



1. Warm 1/4 cup milk to 92ºF, put warmed milk into the transparent glass

2. Dilute 1/4 tsp. calcium chloride (if applicable, see above) into 1/4 cup non-chlorinated water. Add 2 tsp. from this solution into warmed milk.

3. Dilute coagulant or rennet into 1/4 non-chlorinated water (1/4 tsp for Double Strength coagulant or 1/2 tsp. Single Strength Veal rennet). Add 2 tsp. of this solution to warmed milk.

4.  Immediately begin swirling the milk in the transparent glass or cup and begin counting the seconds. You should see "flocs," or tiny white flecks of precipitate, form and stick to the sides of the glass within 20 seconds if your coagulant is still good. If not, your coagulant may have lost too much strength and you will need to refresh your stock, or you may try to experiment and adjust with slightly more coagulant to achieve the needed coagulation strength and enzyme activity.