
TL;DR: Rennet began as an accidental discovery in ancient animal pouches. It is now a multi-billion dollar biotech industry. CRISPR technology allows companies to edit microorganisms to produce 90% of the world’s cheese enzymes without your knowledge.
Started as an Accident
The story of rennet begins between 6,000 and 8,000 BCE. Ancient nomadic herders stored fresh milk in pouches made from the fourth stomach of young calves or lambs.
During travel, the sun’s heat and the swaying motion caused a reaction with enzymes in the stomach lining. When the herders opened their pouches, they found solid white curds and liquid whey. This was the birth of cheesemaking. For thousands of years, this remained the only way you could make cheese.
The Shift to Industrial Production
Cheesemaking was a domestic art until 1874. Christian Hansen isolated the enzyme chymosin for commercial sale. This allowed cheesemakers to produce consistent batches on a larger scale.
By the 1960s, global demand for cheese grew faster than the supply of calf stomachs. This shortage forced scientists to find alternatives. They found microbial rennet produced by naturally occurring molds. These enzymes were vegetarian, but they often made aged cheeses taste bitter. The industry wanted a cheaper, lab-grown copy of animal enzymes.
FPC, CRISPR, and the GRAS Loophole
In 1990, the FDA approved Fermentation-Produced Chymosin (FPC). This was the first bioengineered product in the American food supply.
The industry used a “GRAS” (Generally Recognized As Safe) loophole to get approval. They claimed FPC was “substantially equivalent” to natural calf rennet. This allowed them to skip rigorous safety reviews and long-term human trials. The safety of 90% of your modern cheese rests on a single 90-day rat feeding trial.
Today, companies use CRISPR to edit the DNA of host microorganisms like Aspergillus niger.
- Scientists use these molecular scissors to create super-strains of mold.
- These strains produce chymosin faster and at a lower cost.
- You will not see a GMO label on these products because they are “processing aids.”
- Manufacturers hide these lab-grown enzymes under the word “enzymes” on your food label.
Risks the Industry Does Not Discuss
The purification process is rarely perfect. You should consider these documented health concerns:
- Allergen Risks: Residues from host molds like Aspergillus niger can stay in your cheese. These residues cause respiratory issues and digestive distress in sensitive people.
- Production Impurities: Purification may fail to filter out secondary metabolites. This includes mycotoxins like aflatoxins which are toxic if you eat them.
- Lack of Oversight: Biotech companies test their own enzymes. Independent regulators do not perform the primary quality control.
Brands That Use Traditional Methods
You can choose brands that prioritize transparency and traditional methods. These producers avoid lab-grown enzymes and CRISPR technology:
| Brand Name | Speciality | Key Features |
| Raw Farm | Raw Cheddar | 100% A2/A2, Grass-Grazed |
| Alexandre Family Farm | A2/A2 Organic | 100% Grass-Fed, Regenerative |
| Tillamook | Conventional/Cheddar | Traditional methods for specific lines |
| Rumiano | Organic | Non-GMO Project Verified |
| Dutch Meadow Farms | Raw Cheese | 100% Grass-Fed |
| Origin ROC Milk | A2 Heritage | Regenerative Organic Certified |
| Sierra Nevada | Organic | Grass-fed, Handmade |
| Organic Valley | Grassmilk | USDA Organic Certified |
| Alpine Heritage Creamery | Raw/Handmade | Simply Grass-Fed, Artisanal |
Why This Matters for Your Health
Your food should have a history, not a laboratory patent. Many people in your community find they digest traditional cheeses made with animal enzymes easier than industrial FPC cheese.
If you want a stepping stone to raw milk, start with raw, non-GMO cheese. This transitions your gut and supports traditional farming.
You can find local artisans using traditional methods in our locations or check your local Raw Milk Laws. Learn more about traditional food at the Weston A. Price Foundation or A Voice for Choice Advocacy.
Video: A brie(f) history of cheese – Paul Kindstedt
This video shows how cheesemaking changed from an ancient accident into a global industry. You can see where traditional rennet fits into your history.



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