Studies on ropiness in cultures of Streptococcus Lactis

The production of a ropy condition in milk is a character occasionally shown by the organisms of the S. lactis group. \u27l\u27his character is, however , one that is rather inconstant and its gain or loss or a variation in its extent is frequently noted in the laboratory in cultures that are very probably pure. In starters also, where the S. lactis type of organisms makes up the largest percent of the flora, the development of ropiness occasionally occurs and when ropy starters are carried thru a number of transfers this ropiness sometimes disappears. The change from ropy to non-ropy cultures of S . lactis and the reverse have recently been studied by plating out one of the types, picking colonies and looking for the other among the cultures developing; the results obtained are herein reported

Sources of the flavor in butter

Flavor is one of the important points considered in determining the quality of butter. The sources of this flavor and the exact way in which it is developed are questions which have long been of weight with investigators interested in dairying. The experiments herein reported were carried out with the idea of applying\u27 to these problems some of the information recently secured in a study of starters

Bacteriological studies on two yellow milk organisms

The different milk constituents vary greatly in their susceptibility to the action of the bacteria that make up the flora commonly found in milk. At ordinary temperatures in raw milk, the lactose is soon attacked and acid formed, but if the acid producing organisms are destroyed by some such procedure as heating, pronounced changes soon take place in the casein. The fat is one of the milk constituents that is more resistant to bacterial action, yet even in it striking changes are observed under certain conditions. Some of the common milk organisms, even some of the acid producing types, are able to change the fat, altho frequently considerable periods of time are required for such action

Studies on abnormal evaporated milk

Evaporated milk, which depends for its keeping quality on the destruction of the con tamed micro-organisms by heat, occasionally spoils because of the presence of one or more organisms that resist the exposure employed in the sterilizer. The milk may undergo coagulation, gas formation or various other changes depending on the organism or organisms present. In this paper an unusual type of spoiling, mainly evident as an abnormal flavor and odor, altho there sometimes was coagulation, is reported and the organism causing it is described

Studies of the formation of gas in milk

The gassy fermentation of milk has recently been observed a number of times in the Iowa State College creamery, particularly in the milk set for the manufacture of various types of soft cheese. The isolation and study of the causal organism or organisms was undertaken in several cases and the results obtained, together with a brief statement of the cases investigated, are herein presented

Bacteria and ice cream

The bacteriological standard has proved of value in determining the purity of milk and controlling its supply. Is the counting of bacteria in ice cream equally valuable in determining its wholesomeness and regulating its manufacture? The very great numbers of bacteria generally found in ice cream, in Iowa and elsewhere, make this question important, but it is hardly possible to answer it positively at present. However, in the investigations made by the Iowa Agricultural Experiment Station and set forth in this bulletin these facts appeared: As cleanliness in making ice cream increases, the number of bacteria decreases. It is possible to make ice cream in quantities up to 20 gallons with a low bacterial count without expensive methods, though it is not certain that this is true under large factory conditions. When ice cream is properly hardened its bacterial content will not increase in storage. The chief source of bacteria in ice cream is the cream, although gelatin may add large numbers and the freezer is likely to be an important source of contamination

Bacteriological results obtained in practice with vat pasteurization and with one of the final package methods

The pasteurization of milk and cream intended for consumption as such has now been practised for a considerable period. Many sets of figures are available showing the bacterial content before and after pasteurization with various methods and much information has been obtained relative to the bacterial content of pasteurized milk at the time of delivery. The data on the influence of pasteurization on the bacterial content over considerable periods of time are not so numerous, however, and it was with the idea of securing information under practical conditions on this point that the work herein reported was carried out. The milk studied was that pasteurized in the market room of the dairy department of the Iowa State College for delivery on the route. Two grades of milk are put out-—the one pasteurized by the vat method and the other by the final package method —and a study was made of each