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How to Make Thistle Rennet for Cheesemaking

Did you know that you can make a perfectly good rennet substitute from a weed that might be growing in your yard? 

This recipe uses Bull Thistle (cirsium vulgare), a purple thistle that is considered a weed in most places. Check books on wild foraging or edible weeds for proper plant identification.

Harvesting Bull Thistle

Remove the thistle flower head after it has browned a little on the plant. Pick the head before it starts producing thistle down. Take the flowers in and dry them well in a dehydrator, or merely in a sunny, ventilated place in your house. Once they are fully dried, pick off the stamens or the purplish threads from each head. Put the harvested stamens in a clean, completely dry jar with an airtight lid.

Instructions for Making Thistle Rennet:

  1. Grind dried stamens from bull thistle using a non-porous mortar and pestle. Grind enough to make 5 tablespoons of powder. 

  2. Place the dried and ground stamens in a small bowl. Add warm water (not hot, to avoid killing the coagulating enzymes) to the bowl and steep 10 minutes. The water will be a brown, murky color when finished. 

  3. Strain off the liquid. This liquid is the thistle rennet for use in cheesemaking. Use this liquid in place of animal rennet in the amount of one cup of thistle rennet per gallon of warmed milk.

  4. If not using right away, keep the thistle rennet stored in a tightly covered jar in the refrigerator. For best results, use it as soon as possible. If not using rennet right away, thistle stamens store better dried in a airtight jar in the refrigerator.


How to Use Thistle Rennet in Cheesemaking

  • Thistle rennet should only be used for sheep or goat milk – it will make cow’s milk cheese bitter, especially if aged. 
  • Any cheese made with vegetable rennet may develop a bitter flavor if aged for a long period of time (over 2 months). Solve this problem by using animal rennet for aged cheeses, making cheeses with shorter aging periods when using thistle rennet, or merely eating the cheese younger. 


Ready to Learn More About Coagulants for Home Cheesemaking?




Bull Thistle Flower


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