A Study of Methods of Obtaining Milk Samples for Estimating Milk Fat by the Mojonnier Method

Wide differences in the amounts of milk fat were obtained from some samples of the same milk by the Babcock and by the Mojonnier methods.An examination of the data revealed that the method of weighing the samples of milk and of transferring them into the extraction flask by the Mojonnier method was responsible for these abnormal variations.Though not recognized as official, the Mojonnier method is used extensively in dairy laboratories in this country instead of the RSese-Gottlieb method (1).Some essential details of the technic for obtaining the sample of milk are lacking in the RSese-Gottlieb method (1) and three different technics are used in the Mojonnier procedure (3, 4).The writers were unable to find any data in the literature on this subject, except a statement by Dahlberg, Holm and Troy (2) which is quoted."It was thought that the measuring of samples would introduce slight errors and that fat might rise in the weighing pipette during the time required for weighing to such an extent that extra rich milk might remain in the pipette after the sample was delivered.Both practices were discontinued.After the samples had been heated and mixed until they appeared homogeneous, the milk required for one analysis was quickly poured out and weighed.The samples were weighed directly into the Mojonnier tubes at one laboratory, and at the other, they were weighed into small 25-cc.flasks and transferred to RShrig tubes, using all of the chemicals used in the test to rinse out the flasks."Therefore it was.deemed advisable to compare the different methods of transferring and of weighing samples of milk into Mojonnier extraction flasks. PROCEDUREThe milk samples were heated to 35 to 37.5 ° C. in a water bath at 41.5 to 43 ° C., and mixed by pouring three times from one container to another.The pipettes in all three methods were filled so that the bottom of the menisci were level with the mark on the draw tubes.Each pipette delivered slightly less than 10 grams of milk at 35-37.5 ° C.In method one, four pipettes were filled, the milk sample being poured once into another container between the filling of each pipette.As each