Colonial North America: Countway Library of Medicine

38

Materia Alimentaria

Milk

corodes copper which it does not when sweet, from these facts I am induced to believe the rancidity is owing to the presence of an acid. During the process of churning I believe there is a disengagement of carbonic acid, owing to a decomposition of the milk. The Hottentots make their butter by pouring their milk into leather bags made for the purpose and shaking them until the butter is found. Sugar and Nitre preserve it sweet for a long time, the acid found in butter is the sebacic. Mr Russell tells of a plant in India which deprives butter of its rancidity and when mixed with it preserves it. Rennet is very often used to coagulate milk. Dr Young thought this not to depend on an acid, for when mixed with Volatile Alkali it still preserves this property, also the liver and heart of a turkey, some live fish have this property which they loose when dead, some vegitables will likewise coagulate milk. The milk of herbivorous animals is coagulated by the nitrous acid but that of the carnivorous is not. Rennet I think coagulates milk by the acid it contains, by the same means do children coagulate milk, many authors suppose milk to be only renovated chyle,