Traditionally, cheese enzymes or rennet were derived from the stomach lining of young cows. It was a labor intensive process and contained animal-based ingredients, which excluded vegetarians.
But more recently, around 90 percent of cheeses contain vegetarian enzymes, according to the Vegetarian Resource Group. Through food production innovations, it's become the least expensive option; and therefore, it's the most attractive option for cheese manufacturers.
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Check the ingredient label for “vegetable enzyme or rennet” or “microbial enzyme” to ensure you're selecting the vegetarian option.
1. Vegetable Enzyme
Vegetable enzyme or rennet doesn't contain animal products and is derived solely from vegetables. Therefore, it's considered a vegetarian cheese enzyme. Certain cultures have used fig tree bark, nettles, cardoon thistles, mallow and ground ivy or creeping Charlie.
Enzymes made with thistle are typically used in the Mediterranean to make some cheeses, such as feta, mozzarella and ricotta. The thistle plant is a spiky plant that has a purple or white flowers.
2. Microbial Enzyme
A vegetarian cheese that's derived from microorganisms is called microbial rennet or enzyme. It's made from molds, such as rhyzomucor miehei. This fungus is found in many locations outdoors. The molds are made in controlled conditions in a fermenter, then purified and concentrated so that they aren't unhealthy for human consumption.
Microbial enzymes may increase the bitterness of cheeses, especially in mature cheeses and are a major reason that some high-yielding cheese manufacturers choose genetically modified enzymes.
3. Genetically Modified Enzyme
Genetically modified enzymes are primarily microbial in their base. Types of microorganisms used are bacteria, fungi or yeasts. Even though it can be considered vegetarian, it does feed microorganisms cow genes that produce the enzyme, chymosin.
Any potentially harmful genes, such as ones for antibiotic resistance, are filtered out of the enzyme before it's processed, according to the U.S. Department of State.
And The Vegetarian Society recognizes genetically modified microorganisms as vegetarian-friendly. Genetically modified enzymes not only have a less bitter taste than microbial enzymes, they're less expensive to produce.
4. Vinegar or Citric Acid
Lemon juice and vinegar are also used to congeal cheese. They're usually used in ricotta and for heat-precipitated curd. However, this type of enzyme is rarely used, because of its sour taste.
- U.S. Department of State: "Food Biotechnology in the United States: Science, Regulation, and Issues"
- The Vegetarian Society: "Cheese"
- Applied Microbiology and Biotechnology: "Production and characterization of a milk-clotting enzyme from Aspergillus oryzae MTCC 5341"
- Vegetarian Resource Group: "An Update on Rennet"