176 REPORTS REPORTS. Report to the Local Government Board upon the Effects of Certain Condensing and Drying Processes used in the Preservation of Milk upon its Bacterial Contents. S. DelBpine. (Food Reports, No. 21, 1914. Price 6d.) -Three methods of preservation of milk as practised at four English factories were investigated : A, Manufacture of sweetened condensed milk; B, drying of milk over heated revolving surfaces ; C, drying by spraying the milk into a current of hot air.The main object of the first set of experiments conducted in 1910 was to ascertain whether tuberculous cow's milk was still capable of conveying tuberculosis after being treated by Methods A and B. In the second set of experiments (1911) special attention was paid to the general effects upon the bacterial contents of milk which followed the use of Methods B and C.Method A.-The milk is pasteurised by one of two methods, either at a tempera- ture of from 75' to 80" C. for twenty to twenty-five minutes with continuous stirring in steam-jacketed cylinders, or in a series of steam-jacketed tubes through which the milk is made to pass at such a rate that before it leaves th9 heater the temperature is raised to about 86O C.It is finally filled, after admixture with 11 to 15 per cent. of cane or beet sugar and condensation, into new and clean, but not sterilised, tins. The finished product is about 31 per cent. of the original milk, and should have a total solids of from 74 to 79 per cent., of which about 57 per cent. is cane-sugar. The crude methods used for stirring, cooling, etc., give rise to opportunities for contamination of the milk subsequent to its partial sterilisation.The following are the results of inoculation tests with tuberculous milk after condensation : Before admixture with tuberculous milk, the fresh milk received at the factory did not, on the day of the experiment, contain an appreciable number of tubercle bacilli, but other bacteria were present which caused inflammatory lesion8 when injected under the skin of guinea-pigs.The heating of this milk to 8 6 O C. reduced to a considerable extent this pathogenic action, while a mixture of 1 part of milk rich in tubercle bacilli with 108 parts of the above non-tuberculous milk produced rapidly extensive tuberculosis in guinea-pigs inoculated with it, and after this mixture had been heated to 77O C.it was still capable of producing tuberculosis, but much more slowly and less extensively than the untreated mixture. Further heating to 92' C. left the mixture still capable of producing tuberculosis resembling in type that produced by milk heated to 77O C. None of the sweetened condensed milk prepared from the infective mixture produced tuberculosis in the inoculated animals, but some of the samples caused inflammatory lesions not produced by the pasteurised milk before sweetening and condensing.A full description of Methods B and C for drying milk, together with diagrams of the plant employed, is given, together with an account ofREPORTS 177 inoculation and feeding experiments made with the finished product.The material, as it was collected from the rollers in B, was exposed to considerable risk of con- tamination from dust and from workmen who wear their ordinary clothes and handle the dried milk with their bare hands. The presence of living tubercle bacilli, as found in the milk dried over cylinders heated to 138" C. to 140' C., is at first sight surprising, but it was found by direct experiment that the milk itself never reached a temperature exceeding 96" C., and that only for a period varying from three to six seconds was it a t this temperature.In Method C the milk, after straining and heating, passes to a separator. The separated milk may be dried separately, in which case the cream is removed. When dried whole-milk is wanted, the separated milk and cream are brought together again in a common channel, which carries the milk to a pasteurising apparatus, where it is heated to 70" to 75" C.The vacuum-condensed milk, after reduction to a little less than half its original bulk, is rapidly carried to 95' C., and then at once cooled to 58" C., and forced under a, pressure of 2,000 to 3,000 pounds, together with a current of air heated to 1 1 5 O C., into a tin-lined chamber the internal temperature of which is 76" to 81" C., where it falls in a layer of granules.About 6,000 gallons of milk were treated daily at the particular factory visited. The total number of bacteria present in mixed COW'S milk such as is usually supplied to town consumers was found to be considerably reduced by treatment according to each of the three methods investigated.The reduction was greatest in the case of Method A, and least in Method C. In each .of the three methods of treatment there was a stage at which the reduction in the total number of bacteria, was much greater than that observed in the finished article ready for sale. The increase in the number of bacteria observed during the final stages is due to recontamination, by which is meant the results of the exposure of .a product partly or completely sterilised to sources of infection by which some of the bacteria removed by sterilisation are reintroduced. Were proper precautions taken, such recontamination might be almost entirely prevented, in which case the total number of aerobic bacteria cultivated by the methods described in the paper should seldom exceed 100 per grm.of preserved milk. The reduction in the total number of bacteria was almost entirely due to the death of Streptococci, Staphylo- cocci, Sarcinca, bacilli of the B. coli type, Streptothrichs, yeasts, etc. At none of the stage8 of preparation was the milk ever found completely sterile, and it was observed that the amount of heat to which the milk was submitted was insufficient to bring .about the death of several saprophytic and of some pathogenic bacteria.Among the .saprophytic bacteria which were invariably found to resist pasteurisation, those most commonly detected were sporing bacilli of the types included under the term B. mesentericus. Some Streptothrichs appeared in some cases to have survived, but the evidence was not conclusive.Of tbe pathogenic bacteria, the tubercle bacillus was the only one the fate of which was investigated. Some living tubercle bacilli of bovine origin were found to have survived treatment under Nethod B. It may safely be assumed that Method C, which yields a product giving a higher total bacterial count than Method B, has even less effect upon tubercle bacilli.The same bacilli resisted the process of pasteurisation forming part of Method A. The tubercle bacilli which had survived pasteurisation in Method A, and drying by178 REPORTS heat in Method B, were still capable of producing progressive tuberculosis in guinea- pigs inoculated subcutaneously with milk containing these bacilli, but the course of the disease produced by these bacilli was very much slower than that produced in guinea-pigs inoculated with the same amount of untreated tuberculous milk.The tuberculosis produced by the heated bacilli was latent or occult for some four weeks. Young rabbits fed with milk containing these modified bacilli did not contract tuberculosis. H. F. E. H. Report on the Work of Inspectors of Foods for the Year 1913-1914. A.W. J. MacFadden. (Abstract from the Annual Report of the Medical Officer of Health of the Local Government Board.)-The Report is arranged under the following headings : 1. Work in Special Relation to the Public Health (Regulations as to Food) Act, 1907.-Inspections were made during the year at the majority of the food-importing ports in England and Wales.Reference is made to the prevalence of lesions of actinomycosis in ox tongues imported from Argentina, but great improvement was noticed in the condition of the tongues received after the attention of the Argentine authorities had been drawn to the matter. Samples taken from cargoes of refrigerated meat treated by the formaldehyde process have been examined, the results showing that the amounts of formaldehyde present were not such as would call for action on public health grounds.Ochonocercissis nodules were found to be present in several consignments of beef from Australia. Bags of sugar arriving in the Port of London from Peru were noticed to be covered with borax, which had been carried in the same hold and had become loose during the voyage.This borax contained considerable amounts of arsenic, and steps were taken for the return of a, portion of the sugar which had already been distributed. Apples received from the United States of America during the early part of the year had a bluish deposit on their skins. This deposit contained traces of copper and arsenic, and was evidently the remains of an insecticide wash.Imports of fresh milk during the year were insignificant in amount, and no samples were taken for bacteriological analysis. Of 51 samples of imported cream examined bacteriologically, all except 2 appeared to have been pasteurised before shipment. Boric acid was present in 30 of the samples, and 11 contained hydrogen peroxide. Attention was drawn in the last Annual Report (cj.ANALYST, 1914, 39, 195) to attempts being made by preservative makers to induce dealers and manufacturers of dairy products to use preservatives which are likely to escape detection unless specially looked for. A “special milk preservative ” which has recently been offered consists of sodium benzoate, 69.5 per cent., and sodium carbonate, 28.1 per cent. 2. Local Arrangements for Food Inspection.-More attention is being paid to the supervision and condition of places where food is prepared, and there is a growing tendency on the part of butchers to notify the local authority at once of meat in their possession which is diseased or unsound.3. Bacterial ~ood-Poisoning.-During the year Beveral minor outbreaks of food- Similar attempts are still being made.INSTITUTE OP CHEMISTRY 179 poisoning came under the notice of the Board, but the only serious outbreak occurred at Newcastle-on-Tyne, This was caused by the milk of a cow infected with septicaemia, following parturition having been mixed with the general milk-supply from a farm.4. Work in Relation to the Sale of Food and Drugs Acts.-Inspectors visited a, number of districts during the year, and made suggestions with a view of increasing the efficiency of the work done under these Acts. Added proof was obtained of the disadvantages attaching to the administration of the Acts by the police in certain districts. The methods adopted were of little use for the purpose of detecting modern fraudulent practices, the number of samples taken was quite inadequate, and in some cases the only notes were kept in pocket-books, which mere liable to be destroyed after a short time. As regards the taking of samples under the Acts, it is suggested that an improvement in administration would be effected by frequent conferences between the medical oflicer of health, the anaIyst, and the sampling officer. Circulars relating to Public Health Regulations (Milk and Cream, and Foreign Meat) are published as an appendix to the Report. w. P. s.