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.

Why it's nearly impossible to avoid maltodextrin in fermented dairy.

If you dove deep on our website and clicked on a product to get all the nitty gritty details, you may have noticed the "Honest Disclosure" section. That's right. We believe you deserve to know everything about your food - the big, the small, the good... and even the bad. On most of our fermented dairy (cheese, yogurt, kefir, cottage cheese, etc), you may have noticed a message saying that the freeze dried culture contains a trace amount of maltodextrin 😱 And you may have thought, "What!? I thought they made the most natural food around!" You're right. We do aim to provide you with the most natural foods around, from the farming practices to how they're made in small batches. We want you to have max nutrition and the least toxins possible. And honestly, we're not thrilled to have even a trace of a trace amount of maltodextrin in our fermented dairy. But, sadly, there's simply no way to do that nowadays, especially considering the demand for specific flavors, consistent textures, and a reliable food source. Like seriously, when it comes to maltodextrin, the only difference between Miller's dairy and any other dairy (whether from a supermarket or a farm) is that we did the research and are actually telling you about it. We don't need to. It's not required. But... you deserve to know. So, what's going on with maltodextrin? There's so much more to this story! Keep reading to be a smart natural food shopper and get all the info. What is maltodextrin anyway? Maltodextrin is a sugar, a very simple sugar. Scientifically speaking, it's "short chains of glucose units", a type of "oligosaccharide". Maltodextrin is 100% a lab-produced ingredient. They take a starch (a complex carbohydrate that your body would digest into sugar) and break it down using enzymes or acids. The result is a simple sugar. Labs are basically cutting that long, complex chain that makes up a starch into shorter, simpler segments. Maltodextrin can be made from a bunch of different kinds of starches - corn, wheat, rice, potato, cassava, etc. In the US, it's most commonly made with corn. Depending on what the maltodextrin is derived from and how it's made, it can have different properties and uses. It's most commonly dried into a white powder but can also be found in syrup form. Maltodextrin is used in food as a stabilizer, thickener, anti-caking agent, and bulking agent. I mean, it's in soooo many processed foods. It can also be used in livestock feed or healthcare products as an easily digestible sugar source. Maltodextrin does NOT need to be certified organic in healthcare products (supplements, etc). But, it does need to be certified organic in livestock feed and foods that are certified organic. What would make maltodextrin certified organic? It's how it's broken down. According to OMRI (the Organic Materials Review Institute that approves things for organic use), maltodextrin made with acid is NOT certified organic. Maltodextrin made with enzymes is certified organic. Apparently they believe the enzymatic way is considered "natural". Why would people want to avoid maltodextrin? The FDA classes maltodextrin as a GRAS (generally recognized as safe) food additive. That being said, there are known risks to consuming maltodextrin, especially in larger amounts (which you can absolutely get from processed foods). Here are some potential negative health consequences of overconsumption of maltodextrin: High cholesterolWeight gainType 2 diabetesBlood sugar spikes (particularly in people with diabetes or insulin resistance)Imbalance of gut bacteriaAllergies or intolerances (to corn or wheat) with a range of side effectsExposure to GMOs (when derived from GMO corn) Keep in mind that any of the above side effects typically arise from consuming maltodextrin in large amounts. A trace amount usually won't negatively impact your health unless you have a severe allergy to it (or what it's derived from or made with). What is a freeze dried culture? Freeze dried cultures are surprisingly old. They originated in the late 1800s as a way to preserve the best cheese and dairy cultures and share them over distances. But the technology didn't become really good and reliable until the mid 1900s. That's when they started becoming popular. The process to make them is fairly simple. Like, you can totally do it at home (maybe you've done it with sourdough starter...?). But... for best accuracy and use, freeze dried cultures are best for commercial use and are made in labs nowadays. Here's how it's done: 1- Strains of microorganisms are isolated and grown. The first cultures were made by letting raw milk grow wild. Then, each strain of bacteria, yeast, etc was isolated. This can be done with a particular solution or by putting fermented raw milk on a medium that only supports a specific kind of microorganisms. It's kinda like terrain theory here. Nowadays, labs generally aren't isolating their own cultures much. Instead, they're maintaining cultures separated a longtime ago. It's kind of like culture makers are literal "micro farmers" growing microorganisms. But, instead of planting in the soil, they let each culture grow in pasteurized milk or a specific growing medium (like some kind of something scientific in a petri dish). And, it's 100% in a controlled lab environment. There might be one type of lactic acid bacteria multiplying in one tray and a certain kind of yeast in another. 2- Strains are freeze dried. Each isolated strain is usually freeze dried individually. A freeze dryer is a freezer... but with a vacuum that removes the air. Cool! You could freeze dry anything in a regular freezer, but it would take much much longer. The vacuum element of a freeze dryer makes it so any water turns right into vapor (or dries out) instead of turning to ice. 3- Strains are mixed together to make a specific culture "recipe". It's like a recipe. It might be 3 parts Bifidobacterium lactis, 2 parts Lactobacillus acidophilus, and 1 part Lactobacillus delbrueckii subsp. bulgaricus. The specific strains mixed together are what give each fermented dairy product it's unique texture and flavor. Other ingredients might be added for specific reasons. Sugars (like maltodextrin or sucrose) help keep the culture in good condition and aid it in coming back to life when used. Enzymes (like lipase) might be added to give better flavor. Or colors (like annatto or synthetic dyes) might be added for a desired yellow or orange color. Why is maltodextrin added to freeze dried cultures? In cheese cultures, maltodextrin has a double purpose. It's an anti-caking agent, keeping the culture as a powder... not an unusable clump. It's also a simple sugar that gives the culture something super easy to digest as it comes back to life. Without maltodextrin, freeze dried culture issues would be quite common. They would stop working or have spotty success. How much maltodextrin ends up in the final product? Maltodextrin is used in small amounts in a freeze dried culture. Maybe with some cultures it's more, but with ours, it's less than 1%. Just a little bit is needed. I'm not sure about this with other dairy makers. But, I can tell you how much culture is in Miller's dairy items. For our cheese, about 1/2 tsp of culture is used in 1lb of cheese. For our fresh fermented dairy like yogurt or kefir, about 1 teaspoon of culture is used per quart of milk. There are 96 teaspoons in a pound of cheese and 192 teaspoons in a quart of milk. So, culture alone is 0.5% or less of the final product. And, if maltodextrin is less than 1% of the culture, we're talking less than 0.005% maltodextrin. On top of that, once the culture is added, it eats up that maltodextrin immediately. I mean, that's the whole point. It's a quick simple food to get those freeze dried cultures active again. Let's say that only half of the maltodextrin is eaten by the cultures. Then there would be less than 0.0025% maltodextrin in the final product. Can we round that to zero...? You see where I'm going. This is why we are ok with the level of maltodextrin in our cheese cultures. We absolutely wouldn't choose it as an ingredient. But, as it stands now, the only cultures available have maltodextrin. If you know of one that doesn't, please let me know!!! If I'm NOT shopping at Miller's, how can I find out if maltodextrin is in my food? Maltodextrin is only required on an ingredient list if it's more than 1% of the final product. If it's less than 1%, then it's not required on a food label, because it's considered a "trace amount". 1% and 0.0025% are very different trace amount levels but are treated the same when it comes to labeling. In fact, when shopping for cheese cultures, maltodextrin typically isn't listed as an ingredient. The only way to find out is to look at the Safety Data Sheet or to call the manufacturer and cross your fingers that they'll talk to you. I think that most farms or dairy makers that get this question would simply say, "Nope, there's no maltodextrin." But, that's not the way we roll at Miller's. A few years ago, someone who had a severe allergy reached out about this. It led me down a rabbit hole, talking to the scientists behind our cultures. And now, I'm sharing what I learned with you. Is there a way to make fermented dairy without maltodextrin, like a wild (not freeze dried) culture? Sure, wild cultured dairy is 100% a thing. It's like the sourdough bread of the dairy world. But... as the name implies, the final product can be a bit "wild". This is how we make our bursting kefirs. They're made with real kefir grains (a wild culture) that's been passed down in our community for generations. As this name implies, it can be explosive and super bubbly. It can be quite strong in flavor (not everyone's cup of tea). And it varies a lot from week to week. If we made cheese with culture we saved, it wouldn't turn out the same every time. We wouldn't be able to have a reliable cheddar and gouda and mozzarella... we'd just have one cheese that turns out a little different every time. If we made yogurt with culture we saved, it's a little more reliable. But, it still wouldn't give you the expected texture and flavor of the yogurt you're expecting. And, there would likely be weeks it simply didn't turn out right. Which Miller's dairy products contain trace amounts of maltodextrin and which don't? NO CULTURE = NO MALTODEXTRIN MilkCreamHalf & HalfIce CreamButter ColostrumGhee WILD CULTURE = NO MALTODEXTRIN Bursting Kefir FREEZE DRIED CULTURE = TRACE MALTODEXTRIN CheeseYogurtMild KefirCottage CheeseSour Cream What do you think? Are you ok with minuscule amounts of maltodextrin in fermented dairy? Why or why not? What trace ingredients are you most concerned about? I'd love to hear from you. Comment below to share your thoughts with our amazing community (no account required), or contact us to keep it private 😊 ----- Sources MaltodextrinWhat is maltodextrin and is it safe?Cheese Making Cultures FAQ Cultured Milk Starters

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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Why it's nearly impossible to avoid maltodextrin in fermented dairy.

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