Kamil Perry
Rennet is a key ingredient in cheesemaking, traditionally obtained from the stomach of a calf. This has led to concerns about animal welfare and the extent to which the cheese industry relies on the slaughter of calves. However, rennet can also be derived from other sources, such as plants, fungi, and microbial sources, or produced through genetic engineering. The use of non-animal rennet is becoming more common, with over 80% of cheese consumed in North America being made from non-animal sources.
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What You'll Learn
Rennet is key to cheese-making
Rennet is a key ingredient in cheese-making. It is used to separate milk into solid curds and liquid whey, thereby extending the shelf life of milk. Rennet contains an enzyme called chymosin that is traditionally obtained from the abomasum (fourth stomach) of a newborn calf or lamb. Rennet from calves has become less common, with less than 5% of cheese in the United States being made using animal rennet today. This is because calves are generally separated from their mothers within a day of being born, and most male calves, as well as many female calves, are slaughtered.
However, rennet can be acquired in alternative ways. For example, vegetarian rennet has been obtained from fig leaves, melon, safflower, and wild thistle. Most commercially available non-animal rennet is now produced in laboratories from fungal or bacterial sources. Genetic engineering techniques are also used to extract the DNA that encodes for chymosin from calf stomach cells, introducing it into a microorganism that grows the chymosin in commercial quantities. This product is identical to that produced by newborn calves and is used by cheese producers as a commercially viable alternative to crude animal or plant rennets.
Many plants also have coagulating properties and can be used as a substitute for animal rennet. For example, Homer suggests in the Iliad that the Greeks used an extract of fig juice to coagulate milk. Other examples include several species of Galium, dried caper leaves, nettles, thistles, mallow, and Withania coagulans.
The process of obtaining animal rennet involves drying and cleaning the stomachs of young calves, slicing them into small pieces, and then putting them into salt water or whey, together with some vinegar or wine to lower the pH of the solution. After some time, the solution is filtered, and the crude rennet that remains can be used to coagulate milk.
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Rennet is traditionally obtained from calves' stomachs
Rennet is a key ingredient in cheesemaking, causing milk to separate into solid curds and liquid whey. Rennet contains an enzyme called chymosin, which is traditionally obtained from the abomasum, or fourth stomach, of a newborn calf or lamb. Rennet from calves is less common today, with less than 5% of cheese in the United States made using animal rennet.
The process of obtaining rennet from calves involves drying and cleaning the stomachs of young calves before slicing them into small pieces. These pieces are then soaked in salt water or whey, along with vinegar or wine, to lower the pH of the solution. After some time, the solution is filtered, leaving crude rennet that can be used to coagulate milk. This process is also used for rennet derived from other ruminant animals, such as lambs, which produce a special kind of rennet to digest the milk of their own species.
While rennet is traditionally obtained from calves' stomachs, it is extremely unusual for an animal to be killed solely for rennet production. Instead, the stomachs used for rennet are a byproduct of veal production or livestock butchering. However, the majority of male calves are slaughtered, as are many females, and the calves that remain are used for breeding or milk production.
Today, cheese makers have sought alternative sources of enzymes that can replace animal rennet due to its limited availability and cost. These alternatives include microbial, plant, and fungal sources, such as fig leaves, melon, safflower, and wild thistle. Genetic engineering techniques have also been used to produce chymosin identical to that found in newborn calves, without the need for animal slaughter.
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Calves are often killed for veal production
There are several types of veal, and terminology varies by country. Calves slaughtered for veal can be as young as 2 hours to 2-3 days old, with carcasses weighing from 9-27 kilograms (20-60 pounds). The majority of veal meat produced in the US comes from milk-fed calves. The meat colour is ivory or creamy pink, with a firm, fine, and velvety appearance.
In the past, veal production has been criticised for its cruelty to calves. Calves were often kept in small crates with restricted space to prevent them from exercising, as exercise was thought to make the meat redder and tougher. They were also fed an unhealthy diet of milk or milk replacer, without any solid food, to keep their flesh pale and tender. This could lead to calves becoming seriously anaemic and developing an underdeveloped rumen, which can cause indigestion and enteritis.
However, there have been efforts to improve the welfare of calves used for veal production. Veal crates have been banned across the EU since 2007, and some US states have also made them illegal. Modern veal production facilities in the US provide calves with sufficient room to move and access to bedding and fibrous food. Some veal producers have started to phase out veal crates and use alternative production systems that provide higher welfare for calves.
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Rennet can be extracted from other sources
Rennet is a complex set of enzymes produced in the stomachs of ruminant mammals. It contains an enzyme called chymosin, which is traditionally obtained from the "abomasum" (fourth stomach) of a newborn calf or lamb. However, rennet can also be extracted from other sources.
The limited availability of mammalian stomachs for rennet production has prompted cheese makers to seek alternative methods of milk coagulation since Roman times. Various plants, such as fig leaves, melon, safflower, wild thistle, several species of Galium, dried caper leaves, nettles, thistles, mallow, Withania coagulans (also known as Paneer Booti, Ashwagandh, and the Indian Cheesemaker), and ground ivy, possess coagulating properties and can be used as substitutes for animal rennet. Homer's Iliad suggests that the ancient Greeks may have used fig juice for this purpose.
Genetic engineering has also enabled the extraction of rennet genes from animals, which can then be introduced into certain bacteria, fungi, or yeasts to produce recombinant chymosin through fermentation. This genetically modified microorganism is killed after fermentation, and the resulting fermentation-produced chymosin (FPC) is identical to that produced by animals but is more efficient and cost-effective.
In addition, some soft cheeses are produced without rennet by using acids such as citric acid, vinegar, or lactic acid from soured milk to coagulate the milk. Vegan alternatives to cheese are also manufactured using plant-based sources like soy, wheat, rice, or cashew, which can be coagulated with acids like vinegar or lemon juice.
Today, less than 5% of cheese in the United States is made using animal rennet, and over 80% of cheese consumed in North America is produced from non-animal sources. This shift towards alternative sources of rennet allows for the creation of cheese that is suitable for vegetarians and those with dietary restrictions.
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Genetic engineering can reduce calf slaughter
Rennet is a key ingredient in cheesemaking, traditionally obtained from the stomach of a newborn calf or lamb. The process involves slicing and cleaning the stomachs of young calves, then putting them into salt water or whey with vinegar or wine to lower the pH. The solution is filtered, and the remaining crude rennet is used to coagulate milk. This practice has raised concerns about the slaughter of calves, with some people abstaining from consuming cheese or other dairy products due to ethical concerns.
However, advancements in genetic engineering offer a potential solution to reduce calf slaughter. Scientists have developed techniques to extract the DNA that encodes for chymosin, an enzyme found in calf stomach cells, and introduce it into microorganisms. These microorganisms then produce chymosin in commercial quantities, providing an alternative source for the cheese industry. This genetically engineered chymosin is identical to that produced by newborn calves, and its use can help reduce the reliance on calf slaughter for rennet.
In recent years, cheese makers have increasingly explored alternative sources of rennet due to the limited availability of mammalian stomachs and ethical concerns. Non-animal rennet can be derived from plants, fungi, and microbial sources, making cheese suitable for vegetarians and those keeping Kosher. Additionally, fermentation-produced chymosin (FPC) has gained popularity in industrial cheesemaking due to its lower cost and efficiency compared to animal rennet. FPC is produced by introducing rennet genes into bacteria, fungi, or yeats, resulting in recombinant chymosin during fermentation.
While genetic engineering has the potential to reduce calf slaughter, it is important to consider the potential risks and ethical debates surrounding this technology. Some people may oppose genetic engineering due to concerns about unintended genetic mutations or the impact on animal welfare. Additionally, the use of genetically modified organisms (GMOs) in food production remains controversial, with ongoing discussions about their safety and potential environmental impact.
Despite these concerns, the successful application of genetic engineering in reducing calf slaughter for rennet production can have significant implications for the cheese industry and animal welfare. It demonstrates the potential of genetic engineering as a tool to address specific issues in agriculture and food production while mitigating certain ethical concerns. However, further research, strict regulations, and a balanced approach are necessary to maximize the benefits while minimizing potential risks associated with genetic engineering.
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Frequently asked questions
Calves are generally separated from their mothers within a day of being born, and most male calves are slaughtered. Rennet is traditionally obtained from the fourth stomach of a newborn calf or lamb. However, it is uncommon for an animal to be killed solely for rennet production, as it does not make economic sense. Rennet is a by-product of the veal industry.
Rennet is a key ingredient in cheese that makes milk clump up into curds.
Rennet can also be obtained from microbial sources, such as bacteria, fungi, or plants.
Homer suggests in the Iliad that the ancient Greeks used fig juice to coagulate milk. Other plant sources include nettle, thistle, mallow, and Withania coagulans.
Rennet from calves is not suitable for vegetarians or vegans. However, vegetarian rennet can be obtained from plants and microbial sources.
