Cheesemaking

Addition of Rennet or Coagulant

Someone in ancient times found that the curd or probably the actual stomach of a young calf, lamb or kid clotted milk. Until recently most of the rennet used for cheesemaking was made from calf stomachs (vells). Various plants will also clot milk and there are references to this in early records. These are however not very stable and can cause off flavours in the final cheese.

Nowadays commercial clotting agents are used, many of them based on modified yeasts and some on modified moulds. These react very much in the same way as animal rennet and are accepted by vegetarians.

The process of coagulation or clotting milk is complex, both chemically and physically. Casein is the major protein involved and as it changes its structure it 'encloses' the fat and other constituents. The clot is at first very soft, but as it firms up it contracts and the whey is 'squeezed' from it.

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