Plant extracts have been used as milk coagulants (vegetable rennet) since ancient times: As the Iliad confirms, the Greeks used the juice of fig leaves to coagulate milk. Many countries where cheese is made, such as the Mediterranean regions of Spain, Portugal, North and West Africa and some parts of southern Europe, have a long tradition of using vegetable rennet. Often, these cheeses are made from goat’s milk or sheep's milk, because vegetable rennet may produce a bitter taste in cow's milk cheeses1.
Plant Rennet in Cheesemaking
There are four main sources of rennet: animal rennet (extracted from the stomachs of slaughtered calves) microbial rennet, recombinant chymosin produced by genetically modified microorganisms (GMOs) and vegetable or plant rennet. Historically, most cheesemakers have used animal rennet. Recently though, various factors have led to renewed interest in the use of plant-derived sources of milk coagulants for making cheese. Such factors include the high price and limited availability of ruminant stomachs, dietary regimes such as lacto-vegetarianism, religious restrictions (i.e., Kosher and halal) or the ban on recombinant calf rennet in many European countries (e.g. France, Germany and the Netherlands). Lacto-vegetarians could consider cheese produced using rennet from these three countries as vegetarian.
However, replacing animal rennet with milk-curdling enzymes from plants to make cheese is not the simplest solution. They have a negative impact on the texture and flavour of the cheese and produce a lower cheese yield as compared to other sources of rennet1.
Plants which can be used as a source of vegetable rennet in cheesemaking include Yellow Bedstraw or cheese rennet (Galium verum), thistle cardoon, artichoke and other species of the Cynara genus1,2, stinging nettle (Urtica dioica) and Sodom apple (Calotropis procera).