What is Vegetarian Rennet?

You may be familiar with the term vegetarian rennet, which is often displayed on the label of cheeses. This almost always refers to amicrobial rennet substitute. Microbial rennet is produced by a fungi grown and fermented in a lab setting. This type of rennet works quite well and is cheaper than traditional rennet but can produce a bitter taste in mature cheeses. However this pure microbial rennet has almost entirely been replaced by a more modern version, FPC – Fermentation Produced Chymosin rennet. This version of microbial rennet is made by taking the enzyme-producing gene out of the mammal’s cell’s DNA string and introducing it into a host fungi’s DNA string. This enables the fungi to produce the chymosin enzyme. This fungi can then be cultivated in a lab and fermented, ready to be used as rennet. This genetically modified rennet does not give the bitter flavour in mature cheeses and it is even cheaper to produce. The use of vegetarian rennet is not always advertised on the labels of cheese. The ingredients often just say rennet but, because of its cost effectiveness, genetically modified rennet is used in the production of almost all industrial cheeses. It is important to distinguish this genetically modified organism from genetically engineered foods. When the DNA from the animal is inserted into the fungi, it is not altered, whereas in genetically engineered products the DNA is altered to change its function, altering completely the nature of the gene. There is a third version of vegetarian rennet called thistle rennet. This is the only true vegetable rennet produced from the cardoon thistle (Cynara cardunculus), a species of artichoke. This plant contains an enzyme called cardosin which acts to coagulate the milk in a similar way to the chymosin enzyme. Coagulation takes longer and works better in milk with high levels of protein and fat, so sheep’s milk is perfect. It is most commonly used in Portuguese sheep’s milk cheeses but has also been used for centuries in areas of Spain, Italy and France. Jewish communities were using it to make kosher cheese before the invention of modern rennet substitutes. It gives a particular citrusy and slightly bitter flavour and a more fudgy texture. Some of the most interesting and delicious cheeses are made using this gift of nature