[Report 1951] / Medical Officer of Health, Edinburgh City.

  • Edinburgh (Scotland). City Council.
Date:
1951
Catalogue details

Licence: Attribution 4.0 International (CC BY 4.0)

Credit: [Report 1951] / Medical Officer of Health, Edinburgh City. Source: Wellcome Collection.

    162/198 (page 154)
    MILK SUPERVISION. During the year 747 samples were submitted to the Bacteriological Department of the University for examination, and 267 were examined in the laboratory at Johnston Terrace by the Methylene Blue (Hiscox) Keeping Quality Test. The results of these samples are to be found in appendices 10 and 11. Comparing the results with those of samples taken in 1950 there is a marked improvement in the School Milk, the Pasteurised, Tuberculin Tested (Pasteurised) and Heat-treated Milks, while the results of samples of raw milk, i.e. Tuberculin Tested and Certified, are less satisfactory. With the coming into force on 1st June 1951 of the Milk (Special Designations) (Scotland) Order, 1951, the plate count test ceased to be carried out on Tuberculin Tested (Pasteurised) Milk. The Methylene Blue (Hiscox) Test, which was never an official test, although it was customary to submit samples of Pasteurised and Tuberculin Tested (Pasteurised) Milk to it, is no longer carried out on these grades. Throughout the year small dairies buying non-designated milk in bulk, which they then bottled on their own premises, were persuaded to obtain supplies of bottled designated milk as it was fully expected that the Milk (Special Designations) (Specified Areas) (Scotland) Order, 1951, prohibiting the sale of ordinary milk in the City would come into operation on 1st January 1952. Owing to unforeseen circumstances this Order had to be withdrawn. A new Order, however, was made by the Minister of Food and this came into force on 1st April 1952. By 31st December 1951 only two dairy shops in Edinburgh were selling ordinary milk. On 31st December 1951 “ Heat-treated ” ceased to be a designation. This grade of milk was introduced under the Heat Treatment of Milk (Prescribed Tests) Order (Scotland), 1944, as a temporary measure. The milk was required to pass the phosphatase test which determines the efficiency of the heating process. The machinery did not need to be as elaborate as that for Pasteurised milk. The only dairy in Edinburgh which had a Heat-treatment Licence has now installed a pasteurising plant to comply with the new Regulations. Under the Milk (Special Designations) (Scotland) Order, 1951, a new designa- tion “ Sterilised ” was introduced. The only firm with a licence to produce milk of this designation is the Edinburgh & Dumfriesshire Dairy Co. Ltd. At their premises a completely new plant of 500 gallons per hour capacity has been installed in a separate building. The process consists of selected raw milk being emptied into a stainless-steel receiving tank, from where it is pumped into a 1,500 gallon stainless-steel storage tank. It then gravitates to the clarifier where, by centrifugal force, all foreign matter is extracted. The milk then passes on through the stainless-steel heater at a temperature of 170° F. to the homogeniser. The purpose of the homogeniser is to break up the fat globules into a finer size and to reduce the rate at which they will rise to the surface. In this plant the milk is forced through the homogeniser under a pressure of 4,000 lb./sq. in. The milk is then stored in a stainless-steel tank of 500 gallon capacity : it flows from there by gravity to the vacuum type bottle-filling machine. After filling, the bottles are sealed with a crown cork seal and are then placed in a retort where they are subjected to a temperature of from 220°-235° F. for a period not exceeding 30 minutes. The milk is sterilised in the