Some twenty or thirty different cultures were exhibited, partly obtained from milk, butter and cheese and some from rotting beets etc. The method of obtaining pure cultures with gelatin and agar cultures was explained. The action of some of the bacteria on milk is rendering milk sour. The souring of milk is not due to a single germ, but a large number have the power of changing milk sugar into lactic acid. Of the many lactic acid genus some are especially important in giving the proper aroma to cream, and the butter made from it. Certain species of bacteria render cream bitter. The old Clostridium butyricum was once supposed to be the cause of bitter taste in butter. It has been shown that this germ does not render butter bitter, but there are a number of quite different germs which may cause such changes. Certain peculiar flavors are also due to the action of germs.
Proceedings of the Iowa Academy of Sciences
©1890 Iowa Academy of Science, Inc.
Pammel, L. H.
"Bacteria of Milk, Cream and Cheese, with Exhibition of Cultures,"
Proceedings of the Iowa Academy of Science, 1(Pt. 2), 94-95.
Available at: https://scholarworks.uni.edu/pias/vol1/iss2/39