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What is Rennet?

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What is Rennet?

Rennet or rennin is a natural complex of enzymes produced in any mammalian stomach to help a nursing baby digest mother’s milk. In the food industry, rennet is used as a coagulant – in cheese-making; in certain dairy products, including some yogurts; and in junket, a soft, pudding-like dessert.

Rennet is extracted from the inner mucosa of the fourth stomach chamber of young, un-weaned calves. These calf stomachs are a by-product of veal production (which is an off-shoot of dairy production).

According to the McGraw-Hill Encyclopedia of Science and Technology, “After butchering, the fourth stomach…is removed and freed of its food content.” After this the stomach goes through several steps including being dry-salted, washed, scraped to remove surface fat, stretched onto racks where moisture is removed, then finally ground and mixed with a salt solution until the rennin is extracted.

To obtain rennet using the customary method still used by many European and traditional cheese-makers, stomachs of young calves are dried and “cleaned”, then sliced into small pieces and put into an extraction solution, which will be filtered after several days. In modern production, the stomachs are deep-frozen and ground up before rennet extraction.

Image: Suat Eman /

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Read more: Animal Rights, Conscious Consumer, Diet & Nutrition, Food, Pets, Vegan

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Angel Flinn

Angel Flinn is Director of Outreach for Gentle World – a non-profit educational organization whose core purpose is to help build a more peaceful society, by educating the public about the reasons for being vegan, the benefits of vegan living, and how to go about making the transition.


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3:25PM PST on Nov 9, 2013

To lovely d....drinking milk after age 2 years is unnecessary and unhealthy in humans. .we are the only species that does it 'Milk is acidic and breaks down bone structure it hastens osteoporosis .milking cows is a human thing .they are only meant to provide milk to their young then stop and allow the body to heal. Currently man keeps cows pregnant every year and destroys the cows insides Cows are slaughtered after 4 years of being pregnant constantly then having their babies ripped away from them and standing in fecal lined stalls with painful machines attached to their teats 2-3 times per day. Your lies about needing to milk them are an excuse to make you feel better about the pain you cause

12:23PM PST on Nov 27, 2012

This article just scratches the surface of all the animal suffering in the world.
We are all either part of the problem or part of the solution.
Adopting a vegan lifestyle assures that all animals are safe from pain and suffering.
Being vegan assures you that no matter what you read/see that you are no part of it.
Great feeling!

1:45PM PST on Nov 14, 2011

This is a good article. It's important to educate people about exactly what they're eating.

4:23AM PDT on Sep 24, 2011

It's not the fourth but 3rd stomach being used.
Anyway, a cow normally lives 25 years, in the dairy industry, they rarely go over 8 years (& i'm being generous here!!)
Talking about "natural" the most natural substitute milk for humans is not the cow's milk but the horse milk, which is the easiest to digest for human babies. But please remember that in the so called nature a baby eats hir mother's milk, not the one of another animal.

7:29PM PDT on Sep 3, 2011

My thoughts exactly Paul B. Cows are abused almost from the day they are born until the day they are slaughtered by the dairy industry. Even then we go on to wear their skins. Let's hope that what goes around does not come around to bite us one day.

2:39AM PST on Feb 20, 2011

Lovely, I think you will find that most people on here object to (just for a start), separating mother from calf at a few days old, (have you heard the distress cries of mother cows? they go on for days!), "disposal" of male calves into the cruel veal industry, constant re-insemination so the cow is always productive, and, when production falls off, slaughter of the cow, probably for beef soup, and all so we can "enjoy" the substitute for breastfeeding, which has become marginalised as if for misfits! As for causing pain by not milking the cow, excuse me, but in the natural world there would be a calf there to take that milk! Please, Care2, carry on "dissing"!

12:31PM PST on Feb 16, 2011

I do have a problem with your advocacy against the use of milk as if you are killing the cow to get milk?!
Cow milk is the most natural substitute to human milk and everybody should be encouraged to drink it.
I come from a farming community in India and know for a fact that you are causing immense pain to a cow by not milking it.
Please would you stop dissing milk and milk products in your future columns. Thank you.

2:48PM PST on Feb 2, 2011


9:21PM PST on Jan 26, 2011

OMG......I wouldn't eat veal if my life depended on it and now I find I am contributing to this horrible practice because I eat cheese. I could just throw up!

Thank you so much for this article.....gonna cross cheese off my menu.

9:08PM PST on Jan 26, 2011

Yup. This reminded me of the time that I asked my Dad what the heck rennet was and decided to look up in the dictionary when he couldn't give me an answer. Poor baby cow! I'm so staying away from the cheese now.

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Disclaimer: The views expressed above are solely those of the author and may not reflect those of
Care2, Inc., its employees or advertisers.

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