The milk is delivered in the morning by the farmers at the factory and is weighed and strained through cheese-cloth into the cheese vat. When it is all in the vat it is warmed to a temperature of 86° F. by letting steam into the water surrounding the bottom and sides of the jacketed vat.
A measuring glass and an accurate thermometer are indispensable
The Marschall rennet test
Ripening.—The milk should be slightly acid, not noticeably sour, yet sufficiently ripened for the proper fermentation to take place in the process that follows. The best cheesemakers regulate the ripening by adding a starter to the sweet milk and allowing the lactic acid bacteria to multiply in the milk until a Rennet Test[[6]] or Acid Test[[7]] shows that the desired degree of acidity has been reached. The starter may be sour whey or preferably prepared from sweet skim milk or whole milk with a commercial lactic acid culture as described in Chapter [I] under Ferments and Buttermilk. From 1% to 2% starter is usually sufficient. An acidity of .18% to .20% or 2½ degrees on the Rennet Test is usually desired before the rennet is added.
Christian D. A. Hansen, inventor of commercial rennet extract
Blowing up the rennets to dry them