Rennet, or Runnet, properly denotes the coagulated milky substance which is found in the stomachs of calves, that have received no other nourishment than the maternal milk. It is, however, generally applied to signify the stomach itself, which possesses equal properties.
The rennet commonly employed, consists of the inner membrane of a calf's stomach, which is cleaned, salted, and suspended in paper bags.. Previously to its use, the salt is extracted by washing the rennet, which is soaked in a little water during the night; and, in the morning, the infusion is poured into the milk, with a view to coagulate this fluid. As the preparation now stated, greatly contributes to the superior quality of English cheese, the proper ma-nagement of it ought to be con-ducted with the strictest attention to cleanliness: the reader will, therefore, find a receipt for making an excellent, rennet, in the article CHEESE, vol.i. p. 497..
It sometimes happens, however, that no rennet, sufficiently good for curdling milk, can be procured: hence various plants have been ad-vantageously substituted, and found to answer the same purpose. The principal.of these are the flowers of the Cheese-rennet, or Yellow Ladies Bed-straw (Galium, verum L.) used in England ; and the Car-doon (Cynara cardunculus L.) in Spain. A strong infusion is made of the down of the latter vegetable in the evening ; and, on the succeeding morning, half a pint is poured among fourteen gallons of new milk, which is thus effectually coagulated, and in consequence produces a delicious cheese.