What is Rennet and Should I Eat It

shredded cheeseAFTER READING BRUCE BRADLEY’S POST ABOUT tricks of the food industry trade, I promptly freaked out over the fact that I’d been eating calf stomach – rennet – in my cheese. After maniacally checking the labels of all the cheese in the house, I calmed down enough to turn to my best defense when I’m faced with a food crisis – looking for answers.

Rennet is a complex of enzymes found in the stomach of baby mammals that allows them to process mother’s milk. According to Wikipedia, the active enzyme in rennet is called chymosin or rennin but there are also other important enzymes in it such as pepsin and lipase.It is used in cheese makingto speed coagulation and separate the curds and whey after the starter culture is added to the milk.
There are different types of rennet:Animal rennet comes from the stomach of newborn calves, lambs, and kids (the baby goat kind, people, don’t freak out.) The enzymes needed are only found in the fourth stomach of the ruminants before they are weaned. For cheese making, rennet from the animal providing the milk is used (calf rennet for cow’s milk cheese for example.)There is a traditional way to get animal rennet, which involves combining the stomach of the animal with salt water or whey along with wine or vinegar. Some traditional cheese makers in Europe still use this method.

Then there is the modern way to get animal rennet involving deep frozen stomachs, enzyme-extracting solutions, and stomach acid. Interestingly, there could be trace amounts of Sodium Benzoate in rennet produced this way.

Animal rennet can also be genetically engineered by inserting cow DNA into certain bacteria, fungi, and yeasts – no baby animals harmed. According to Wikipedia, genetically engineered rennet has about 80% of the market share and as of 2008 “approximately 80% to 90% of commercially made cheeses in the US and Britain were made using GM-based rennet.

Vegetable rennet can be made from a variety of plant sources such as fig, thistle, safflower, and dried caper leaves. It can also be made from genetically modified soybeans. Since there is no worldwide industrial production of vegetable rennet, it is often made from microbial sources.

Microbial rennet is made from molds (although there is no mold in it.)

Well, that all depends on what your concerns are.

If you are vegetarian, then avoid any cheese with rennet, animal rennet, or enzymes (which typically means animal rennet, although not always, but there’s no easy way to know) listed in the ingredients. Vegetable rennet will be listed as such, same with microbial rennet.

If you try to avoid GMOs, well, it’s a little tougher. Organic cheeses won’t have GMOs. But since genetically engineered rennet doesn’t have to be labelled, you have no way of knowing whether the rennet is genetically engineered or if the vegetable rennet comes from GMO soybeans. Stick with microbial rennet cheeses, traditionally produced cheeses, or organic cheeses.

With regard to GMOs: the cows, sheep, or goats are being fed GMO corn or grain will also have an impact on the overall GMO-ness of the cheese. There is just no good way to know unless you buy organic.

If you are concerned about baby animals being killed for rennet, stick with cheeses using vegetable or microbial rennet sources. Although remember, 80% of the rennet is genetically engineered without the use of baby animals.

If you are lucky enough to live near a Trader Joes, they have thoughtfully provided this informative web page detailing which of their cheeses contain which kind of rennet. (Remember, it doesn’t tell you anything about GMOs.)

Using vegetable or microbial rennet could effect the flavor of cheese, so if you are a cheese purist or aficionado, you’ll want to take that into consideration.
THE BOTTOM LINE: Decide what’s important to you with regard to rennet and purchase accordingly. Read the ingredients!
UPDATE: Reader Jennifer recently sent along this information regarding Trader Joe’s products. Thank you, Jennifer!
“Since 2006 any product labeled with the Trader Joe’s name does not contain any GMO’s, nor does any of their produce, which does not always have their name or label on it. Also, since 2006 none of their house-labeled products contain high fructose corn syrup or hydrogenated oils, either. They do carry some national brands over which they don’t have control so the same guarantee cannot be made with those, but they have strict requirements on their own products and conduct independent testing to ensure all of their standards are being met. They are very helpful if you have any questions. “

4 comments for “What is Rennet and Should I Eat It

  1. Walt
    March 5, 2012 at 9:00 am

    Here’s an interesting article about the possible orgins of rennet.


  2. cat
    March 5, 2012 at 12:23 pm

    Thank you, Walt.

  3. bstacey
    May 19, 2012 at 2:15 am

    This rennet is an extremely powerful enzymes when you consider the minute amounts used to harden cheeses.What may be of concern is the effects of this enzymes on calcification and effects on calcium in the human body after eating this .
    For instance does it play a role on hardening of the arteries and the build up of plaque in the venous tree?

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