Should I choose animal rennet or vegetable rennet in my natural cheese?

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January 23, 2025

Miller’s Bio Farm is all about giving you TMI about how your food was produced. Because, in today’s food world, you can’t just rely on labels alone.

When you shop our A2/A2 CHEESE, you can click on each cheese and see the full product description. You can find the exact kind of rennet in the ingredient list. And, you can see any trace additives used in the cultures or rennet listed in the “Honest Disclosure” section.

But what does that all mean, and which type should you choose? How would you know which type is used? That's what we're delving into in this blog post -- it's all about rennet!!!

What is Cheese? What is Rennet?

Legend has it that cheese was discovered by mistake, when someone used a flask made of lamb stomach to bring some nourishing milk on their travels. After walking for days in the hot sun, he found that the milk in his flask had curdled… and it was delicious! The raw milk naturally fermented, and the enzymes in the lamb stomach coagulated the curds.

Cheesemaking has come a long way since then, with specific processes and cultures needed to make different kinds of cheese. And then of course there’s regulations around food and food safety and modern expectations for consistency and affordability.

Here's an overview of how cheese is made today --- You add culture to milk and let it ferment. Then, you add rennet, which separates the milk into curds and whey. Then you press the curds and age them. Voila cheese!

Sure, you can also use vinegar or citric acid to curdle the milk for fresh cheeses like paneer, ricotta, or even mozzarella. But, for aged cheeses, you need to use rennet. It's essential.

Rennet is a complex set of enzymes that are naturally produced in the stomachs of ruminant mammals. Chymosin, its key component, is a protease enzyme. In addition to chymosin, rennet contains other enzymes, such as pepsin and a lipase.

The enzymes in rennet target casein, the main protein in milk. They cause the casein molecules to divide and re-coagulate into even larger clumps (AKA cheese curds).

Above photo of how the cultured and fermented milk sets after rennet is added.

Above photo of how the curds and whey look after the curds are cut and heated a bit.

Above photo of how the curds look after the whey is drained, before pressing the cheese.

Types of Rennet

Veal/calf rennet: Made by grinding calf gullet/stomach and mixing it with salt. The powder is put in a solution that extracts the chymosin. It’s typically made as a liquid rennet.

Veal/calf rennet is the most natural form of rennet, since it’s the oldest form of rennet. Remember, carrying milk in a lamb stomach was likely how cheese was discovered!

Using veal/calf rennet in today’s world is not all pure and natural. Most rennets available are made from calves that are a byproduct of the conventional dairy industry. They are not likely born from happy, pasture raised cows that are 100% grass-fed. And, almost all of them contain trace additives of one kind or another. These may include sodium acetate, propylene glycol, or potassium sorbate.

Fermentation-produced chymosin (FPC): It’s a genetically modified organism! They splice genes in a mold to produce chymosin.

I spoke with a lab tech that makes the vegetarian rennet used in our goat cheeses. They weren’t sure how they can make the claim that it’s GMO-free, but somehow the rennet and cheese companies make that happen (with a lot of * and fine print below).

Fermentation-produced chymosin is the most popular rennet for certified vegetarian” cheeses. Over 90% of all cheeses made today use this kind of rennet. It makes a good product. As it stands now, it cannot be used in "certified organic" cheeses.

The concern here is of course that it’s a bioengineered ingredient. What are the long term health consequences of consuming it? Does the GMO chymosin enzyme alter the casein proteins differently than veal rennet? Well, there’s simply not enough research done to be 100% sure.

Another concern is trace additives like sodium chloride or sodium benzoate.

Microbial rennet: Made when Rhizomucor miehei mold grows on a nutrient base that’s primarily soy. Yes, that’s right, soy. And, that means that the nutrient base is most likely GMO!

Mold rennet is also used in “certified organic” and “certified vegetarian” cheeses. However, it’s not the best. It tends to produce undesirable bitter flavors. It also does not age very well.

Recent research is showing that microbial rennet can have a negative impact on the gut long term. It’s definitely something to be cautious about until a lot more research is done.

Rennet Alternatives:

You can use squares of dried salted calf stomach, which has been done for thousands of years. You can use thistle, which is traditionally used for specific cheese in Spain and Portugal and is really expensive. You can also make soft cheeses from wild rennet from plants like sorrel, cardoon, artichoke, and fig.

However, these rennets are typically used for making cheese at home. They would not produce a cheese that’s consistent, tastes good, and holds up well. Most farmers and cheesemakers would not want to dabble with them, as they’d end up with a lot of waste and unhappy customers.

Is GMO Vegetarian Rennet Safe?

The safety of genetically modified rennet is a topic of debate, both in the scientific world and the regulatory world. Some studies suggest that it’s completely safe, and others raise concerns about potential allergic reactions or other concerning health consequences (read more about corn and soy and allergies in this post).

Why the debate? Well, there’s limited scientific data to definitively state the long-term safety of cheeses made with GMO rennet. In my opinion, it’s likely best to wait for full safety studies before introducing a product. Sadly, that’s not how our food world works. So, now that you know, it’s your choice whether you want to stay away from "vegetarian rennet" or not!

It’s important to note that the safety and regulatory status of GMO rennet varies from country to country. While in some places, GMO rennet has been deemed safe and approved for food production, in others, it might be subject to restrictions or even prohibited altogether. Depending on local laws, cheese made with GMO rennet can be labeled as GMO-free (and that’s how it is in the US).

Labeling Requirements

With cheese, it’s required to list “rennet” or “enzymes” as an ingredient. But, the source (animal, plant, or microbial) is NOT required. For cheese companies that make cheese with vegetable rennet, the have the option of listing “vegetable rennet”. But again, the exact kind is not required on the label.

Additionally, listing the ingredients in the ingredients is also not required. For example, a cheese may say "rennet" in the ingredients list, but the sodium acetate, propylene glycol, or potassium sorbate or other additives does NOT need to be listed on the label. The same is true for basically any trace additive in food.

So, if you want to know the type of rennet or trace additives in your cheese, you need to read the product description. If it's not there, you'll need to ask.

What’s in Our Cheese?

At Miller’s Bio Farm, we of course go above and beyond. We do everything we can to avoid the greenwashing or confusion caused by food labels. Instead, we just tell you everything we can about how the food is produced. We include an honest disclosure for each of OUR A2 CHEESES, which tells you the type of rennet and any additives in them (and not just what's listed on the Safety Data Sheet, we actually talk to the rennet and culture companies about it).

For all of our cow and goat cheeses (except mozzarella), beef rennet is used. The calf gullets used in our rennet are sourced from milk-fed veal calves mainly from New Zealand and Australia.

Sadly, it seems impossible to find a beef/veal rennet without trace additives. We were super excited to find Walcoren brand rennet, which did not have any additives on the safety data sheet. But, when I called the company and talked to a scientist, he confirmed that the standard additives are actually in it. Since they're a Canadian company, they don't need to include them in the safety data sheet. Ugh.

As with all beef or veal rennets, our rennet contains trace amounts of sodium acetate, propylene glycol, and potassium sorbate.

For our mozzarella cheese, a microbial vegetarian rennet is used. It's organic and simply makes a better mozzarella. It has trace amounts of sodium chloride and sodium benzoate E211.

For our cottage cheese, no rennet is used at all. It's cultured, and the curds are separated with a little heat only.

To put all of this into perspective, you only need a little bit of rennet to make a whole lot of cheese. For example, our cheesemaker uses 60ml of rennet per 1,000 pounds of milk. That’s 1.93ml per 1 gallon of milk. Then, the curds are drained and pressed and fermented. In the end, In 1 lb of finished cheese, there's about 0.00066 grams of rennet.

Any additives would be minuscule, a trace of a trace amount. But, if a trace of a trace amount of something bad is in everything you eat, it's no longer a trace amount!

Regardless, you deserve to know everything about your food. So, now the cheese and rennet choice is yours!

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*Originally posted on 7/28/23. Updated on 1/23/25.

Warning: Fat Holds Toxins. Carnivore and keto folks should watch out.

Aaron, myself, and a couple other team members went to Tennessee to participate in Meatstock 2025 last weekend. It's a carnivore/keto party in the Smoky Mountains. Boy, we learned a lot and met a lot of wonderful people, both people who healed through food as well as doctors and experts that help people heal. One person we had the pleasure of meeting was the amazing Dr. Kiltz. He's a carnivore. He's also a doctor who specializes in fertility. And can you guess how he helps many of his patients? Yup, through food. He's a big supporter of the carnivore and keto diets. He suggests getting 70-80% of your calories from fat, 15-30% from protein, and 0-10% from carbs. Dr. Kiltz spoke at a dinner we attended. And something he said shocked us -- "Don't worry about grass fed, regenerative, and all that natural stuff. It's the fact that you're eating fat that matters." 😳 Woah woah woah. Hold up a sec. We, of course, had a conversation with Dr. Kiltz about this. I mean, why are people having health issues in the first place? Sure, some of it could be genetics. Some of it's definitely environmental. But, a lot of it is likely the food we're eating. It's processed food laden with seed oils and carbs and sugar and yucky additives... but also the farming practices that result in toxic stuff hidden in plain old ingredients. Dr. Kiltz agreed and elaborated on his statement. What he's saying is that, if you're eating a standard American diet, the biggest and fastest impact you can make comes from altering your diet on a macro level - fat, protein, and carbs. But the granular stuff you can't see or count matters too, especially once you're making progress. OK, I get it. But then I thought some more... Toxins accumulate in the fat. So, if you eat animal-based foods (especially the fattier ones) and are looking to limit (or eliminate) that awful toxic stuff, farming practices matter. Like a lot! So, unsurprisingly, I went into research mode. Here's what I learned. Which toxins accumulate in fat and why? Not all toxins accumulate in fat. Some are stored in bone, muscle, organs, etc. But, there are certain toxins that a body stores specifically in fat. They include: Dioxins and furans (PCDDs/PCDFs) - These are persistent pollutants, resistant to breakdown, that are generally creating by burning things like plastic and chemicals and garbage. They can also be created as byproducts of industrial processes.PCBs - That's short for polychlorinated biphenyls, which are synthetic chemicals that were used to make various consumer products, from paint to glues to lubricants to coolants to batteries. They were banned in 1979, but because of their inability to breakdown, they remain as toxins in our environment.Pesticides & Herbicides - This includes previously banned pesticides (like DDT) that are still present in our environment. This also includes pesticides used today, like organochlorine and organophosphate pesticides. Certain Toxic Heavy Metals - Mercury, lead, cadmium, and aluminum are known for accumulating in fat. The reason the above toxins collect specifically fat (AKA adipose tissue) is because they are lipophilic. Liophilic is when a substance is "fat loving" and can bond with or dissolve in fat. Other toxins are hydrophilic, meaning they are "water loving" and can bond with and dissolve in water. These include bentazone, glyphosate, imidacloprid, flouride, and arsenic. They do not accumulate in fat. What can an overload of toxins do to your body? I like to think about toxic overload like a cup. Our bodies can process a little of it. But, when the cup is overfilled with stuff like pesticides, toxic heavy metals, mold, carcinogens, etc, that's when problems happen. Our bodies are pretty good at handling stress. That's why toxic overload can be confusing. It may take a long time - months, years, or decades - for the problem to arise. Then, once the problem happens, it's hard to pinpoint the cause. And then, healing time is often lengthy (and sometimes the damage can't completely be undone). When it comes to toxins, the response really depends on the body. The list of issues that can arise is exhaustive. They include fatigue, headaches, digestive problems and leaky gut, brain fog, anxiety and depression, increased risk of cancer, cardiovascular disease, hormone imbalance, mast cell overreaction, histamine responses, bloating and inflammation, trouble sleeping, skin conditions, liver damage, obesity, and more. Where can toxins in animal-based foods come from? When it comes to farming, there are few places that toxins can be introduced to animals. This can be from toxins resistant to breaking down from decades ago or toxins being used or produced today. This can be on the actual farms or in the facilities that prepare food for sale: Air: Toxins can vaporize and float in the air. Animals can breathe it in or it can settle on top of soil or water. Water: This is especially true with city water, which often has chemicals added to it or may run through old pipes. But, as we all know, water pollution varies from area to area.Soil: This can come from the local area or a non-farming activity that happened on the land previously. This can also be from past farming practices or current ones. Slaughter and butchering: Did you know an antimicrobial is required by the USDA when processing meat? Processors can choose harsh chemicals like bleach or opt for more natural ones like citric or lactic acids or vinegar.Recipes: Think beef jerky or lunchmeat. They have ingredients. First off, anything that's less than 1% doesn't need to be listed on the package. And then, of course, there's the hidden stuff depending on the quality of the ingredient.Packaging: Even what our food comes in can leach chemicals into our food. I mean, think about microplastics in bottled water! When toxins enter your food, you can't see them. You can't taste them. You can't smell them. This is why knowing more about how your food is produced is important. How can farming practices decrease the levels of toxins? Well, there are bunch of ways toxins can get into food from farming. Here are some ways that farms can decrease toxins in the final food: Choose A Clean Location: If a farm is located right next to or downstream from a factory or city, toxin levels will likely increase. Farms should ideally be far from cities or factories. Have Clean Water: If contamination is persistent in your area, you'll likely know it. And, you can always test the water, too.Improve Soil Health With Regenerative Farming: When soil is dead and unhealthy, toxins break down at their normal speed. But, with regenerative farming that creates robust microbiology, toxins can break down faster.Fertilize Naturally: There are plenty of chemical fertilizers out there. But, compost and manure from natural chemical-free sources are just as good… if not better.Limit, Eliminate, Be Considerate With Pesticide And Herbicide Use: A grand majority of farms still use pesticides and herbicides regularly. Yeesh. Even the organic ones can contain yucky stuff. With things like fruit, it's kinda necessary to some extent. But, especially with pasture raised animals, they're simply not needed (even though some farms still choose it).Choose Naturally Formulated Feed: This is the idea of the ingredients in the ingredients. You can have the most pristine land, air, and water, raising beef. But, if you feed them GMO corn sprayed with glyphosate and grown in contaminated soil... well... those toxins are introduced. Farms can make sure they're feed ingredients are pure and the sources the ingredients come from are chemical-free.Eliminate Vaccines: Yup, vaccines contain toxins. And especially when injected, they can harbor themselves in fat. Aluminum is a common ingredient in vaccines. And, did you know that animal vaccines can contain Thimerosal (AKA mercury)? That's been banned in human vaccines. When animals are raised outdoors and to be naturally happy and healthy, vaccines aren't necessary.Be Mindful With Anyone Who Processes Your Food: This can be a challenge, especially if you're in an area with more conventional farms. Farms can ask the hard questions and ask for changes like what antimicrobials are used (apple cider vinegar is allowed by the USDA), what the ingredients are, and where the ingredients are sourced from. At Miller's Bio Farm, we try to reduce your toxic intake as much as possible. Here's a few notable things we do (among the many): All of our small farms are 60+ miles from any major city.Our pastures are never sprayed with pesticides or herbicides. We love the biodiversity!Our pastures are fertilized with manure and more manure!Our farms that raise our animals regenerate their soil year after year. The idea is to improve the quality of the soil, and that includes the microbes that can help break down toxins.Clean well water is used for the animals to drink and for processing our meat and all of our products. Our beef, pork, and lamb are washed with organic apple cider vinegar. Our chicken is air chilled. Our turkey is washed with water and only water.None of our animals are fed corn or soy. And, our feed is chemical-free.Our farmers do not vaccinate their animals. Our chicken and turkey and lamb is 100% vaccine free. The only way a vaccine could be given to a cow or pig is if the animal was bought in and previously vaccinated. We make sure that no animal has received an mRNA vaccine. None of our products have yucky stuff like nitrates/nitrites, additives, fillers, etc. It's simple natural food. We always vet our processors before working with them to make sure they're up to our natural standards. We'd love to supply you with clean foods and hope you join the movement! Do you eat a lot of fat? Whether you do or not, what toxins make you most worried? I'd love to hear from you. Comment below or contact us 😊 ----- References: Carnivore Diet Macros and How to Achieve ThemAdipose Tissue as a Site of Toxin Accumulation Pesticide residues in animal-derived food: Current state and perspectives Impact of pesticide exposure on adipose tissue development and function10 Powerful Nutrients Found Only in Meat

Should I choose animal rennet or vegetable rennet in my natural cheese?

What is Cheese? What is Rennet?

Types of Rennet

Is GMO Vegetarian Rennet Safe?

Labeling Requirements

What’s in Our Cheese?

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Warning: Fat Holds Toxins. Carnivore and keto folks should watch out.

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