This section is from the book "Practical Dietetics With Special Reference To Diet In Disease", by William Gilman Thompson. Also available from Amazon: Practical Dietetics with Special Reference to Diet in Disease.
Of recent years the use of pepsin for predigestion of milk has been gradually superseded by that of pan-creatin, which acts best in an alkaline medium. This ferment, like pepsin, may be preserved almost indefinitely in powdered form. Milk thus prepared is slightly yellow and less opaque than raw milk. The process may be conducted as follows:
Add a pint of fresh milk to a gill of cold water in a clean vessel. Put in a tubeful of Fairchild's " peptonising powder" (pancreatic extract 5 grains, and sodium bicarbonate 15 grains), or, instead of the pancreatic extract, substitute 1 to 2 drachms of "pancreatic solution" made by Parke, Davis & Co., stir well, and place in warm (not boiling) water for half an hour or until a slight bitter taste is present.
This taste means that fermentation has proceeded far enough. To allow it to continue will make the milk unpalatable, and it is almost impossible to disguise the bitterness. Boiling for two or three minutes stops all further fermentation, and the milk should then be placed on ice until ready for use. Such milk will keep well for several hours.
When used, serve alone cold, or add carbonic-acid water to disguise the taste. For adults a little coffee may be used for the same purpose.
To a pint of cold fresh milk add a pint of, thick milk gruel, boiling hot. The gruel may be made of sago, pearl barley, arrowroot, oatmeal, wheat flour, or other farinaceous food, according to taste. The temperature of the mixture should be about 1250 F. Add a tubeful of peptonising powder (15 grains), and place on the side of the stove for two or three hours, avoiding great heat. Then boil to stop the fermentation. Strain, and keep on ice ready for use. The gruel disguises admirably the taste of the milk.
When pancreatinisation is long continued the casein is completely digested, but the milk becomes too bitter for use.
Legumin is a vegetable ferment which is said to make milk highly digestible for invalids by converting casein into a soluble albuminoid. This substance, which was lately introduced by Bovet, is also given as a food.