On the Producing of Milk having a Low Bacterial Content.
About a year ago the specific opportunity which our laboratories had been seeking presented itself. We were brought into touch with a farm on the outskirts of Vancouver engaged in the production of milk and the distributing of the same in the city. The proprietors of the farm, with at that time a herd of twenty-five grade cows, were endeavouring to supply a high grade milk, a milk having a low bacterial content, and secured from cattle giving a negative reaction to the tuberculin test. We approached the proprietors, Mr and Mrs Alexander Hill, and found that they were desirous of co-operating with us. At the same time their milk was obtaining a premium over the usual price obtained for market milk sold in the city. We made it clear that we were anxious to secure data which would be of use to milk producing farmers generally with respect to the possibility of producing a high quality milk; and they-Mr and Mrs Hill-assured us that they desired to have advice and help if the same could be forthcoming. Finally we made the following arrangement: (a) we were to be permitted to obtain samples of milk at any time deemed most suitable to ourselves, (b) these samples were to be examined for bacterial flora to the end that we might secure the data we needed, (c) no report on the examinations was to be sent from our laboratories until it became possible for us to publish the data as a whole, (d) the proprietors of the diary were to be given any information that was available from the laboratory data, but, under no circumstances, was the same to be used for publicity purposes, (e) we were to check up any of the procedures in vogue on the farm and dairy as far as proved to be possible without unduly interfering with the progress of our main project. The arrangement was agreed to mutually, and it is a matter of gratification to us that throughout the entire investigation the conditions detailed above were subscribed to loyally.We conducted preliminary work in February and March, 1923, and the investigation proper commenced on April 10th, 1923, and continued until July 24th, 1923(2).The farm premises would be held to be well below the average of what are usually considered to be suitable holdings for the production of milk. In the paper (loc. cit.) a description of the premises, of the methods and procedures followed by the proprietors and of the system adopted by them in the cleansing and sterilization of utensils, are given in detail. A milking machine was used throughout. A small quantity of the first milk was drawn into a separate pail and in all cases this was used for the feeding of certain livestock. The milking as such was done with the machine. Stripping was done by hand and the strippings were mixed with the milk supply.Throughout the period during which the work was carried on, 90 samples of milk were examined, three samples being taken on each of the 30 days when determinations were made. At each sampling, two pint bottles of milk, intact, as bottled by the dairy, were taken by us on the premises. One bottle was of evening's milk-designated I in Table, and one was of morning's milk-designated II in Table. The bottles were chosen at random, and usually were obtained by us at 8.30 a.m. In addition, a sample of morning's milk after cooling and prior to bottling and representative of the entire supply, was taken-designated III in Table. The media employed for the plate counts was the Bacto-purple-lactose-agar (dehydrated) of the Digestive Ferments Company. For detecting lactose-fermenting (gas-producing) types we employed MacConkey's neutral-red-bile-salt-broth. All determinations were done in triplicate. Triplicate plates were incubated at 37 degrees C. and at 22 degrees C. respectively. The former were counted after 48 hours' incubation and the latter after 5 days' incubation. For the fermentation tests, triplicate tubes containing 20 c.c. of milk in each case were submitted to the fermentation test at 37 degrees C. and at 22 degrees C. respectively. For the reductase test triplicate tubes containing 20 c.c. of milk and 0.5 c.c. methylene-blue in each case were submitted to the methylene-blue-reductase-test at a temperature of 37 degrees C.
Sadler
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W
Kelly
C D
CD
Martin
G R
GR