Rennet and coagulants are preparations of proteolytic enzymes, some of which have been used in cheesemaking for thousands of years, and they seem to be the oldest known application of enzymes. The earliest indication of cheesemaking descends from cave paintings around 5000 bc. Historically, most enzyme preparations used for cheese have been extracts from the stomachs of ruminants, but coagulants from microbes and plants were also used at very early dates. It is likely that cheesemaking was invented by accident, when nomads travelled on hot days with milk kept in bags made from the stomachs of ruminants, Camelus dromedarius most likely. If the milk was left undisturbed, clotting of the milk occurred due to the developed acidity as a result of bacterial activity and possibly due to the presence of clotting enzymes originated from the stomachs used as bags. As a consequence, a soft coagulum was formed, and some of the liquid phase (whey) was absorbed into the skin or seeped through the bag and was lost by evaporation (Tamime, 1993). Hence, partial concentration of the coagulum took place and further concentration by hand squeezing and sun drying. However, by introducing standardised rennet in 1874, Chr. Hansen in Denmark was the first to sell a commercial enzyme product.
The nomenclature of enzymes is marked by the long history, during which the nature of enzymes was realised, and knowledge about their identity and diversity gradually in- creased. Originally, enzymes extracted from the stomachs of young ruminants were used and characterised. The first name for the milk-clotting enzyme was chymosin, derived from the Greek word for gastric liquid ‘chyme’, given by Deschamps (1840) to the main enzyme from the fourth stomach of the calf. In 1890, the name rennin, derived from the word rennet, was suggested for the same enzyme, and for many years it was adopted in English-speaking coun- tries (Foltmann, 1966), as well as in international enzyme nomenclature. Due to confusion with the related proteolytic enzyme renin, the main milk-clotting enzyme was again named chymosin (International Union of Biochemistry and Molecular Biology – IUBMB, 1992).
Cheese is produced by milk-clotting enzymes of different origin. The active milk-clotting enzymes in all rennet and coagulants, which have been found successful for cheesemaking, are aspartic proteinases having the IUBMB number EC 3.4.23.
The original rennet preparation is, by definition, an extract of ruminant abomasums (Andre ́n, 1998); it is commonly called animal rennet. This definition is now generally accepted, and it is agreed that the name ‘rennet’ should be reserved for enzyme preparations from ruminant stomachs, whereas other milk-clotting enzymes should be named ‘coagulants’, The common group names are microbial and vegetal coagulants, respectively. It is also
Technology of Cheesemaking, Second Edition Edited by Barry A. Law and A.Y. Tamime © 2010 Blackwell Publishing Ltd. ISBN: 978-1-405-18298-0