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30 EKENBERG POWDERED MILK. The manufacture of Ekenberg powder- ed milk, which has been generally intro- duced aboard lake vessels during the past season, is thoroughly described in a re- cent issue of the Scientific American. It is now about five years since Dr. Martin Ekenberg, the eminent Swedish scientist, delivered a lecture before the Royal "Academy of Agriculture in Stockholm describing the process which he had then just envolved for the production of dried milk in an entirely new. form, and in which the constituents of the liquid were perfectly retained. Since that date sev- eral improvements in the process have been effected and at the present time 'there are several factories in Sweden and other countries where the production of the milk powder is being carried out on an extensive commercial scale. While there is no food which can take the place of milk in its various uses, there is at the same time no dietary article which is more difficult of distribution, as it is extremely sensitive, and liable to rapid changes and. sour fermentations. The reason is that the liquid is composed of 88 per cent of water. in which the solid food substances are dissolved and suspended; and among these latter sub- stances there is one most subtle class, i, e., the albumenoids. It is clear that the great amount of water present rend- ers the milk remarkably susceptible to the propagation of bacteria, while at the same time its bulk militates against cheap and easy transportation. Numerous efforts toward preserving the solid substances present by the elimi- nation of the water have been made since the early years of the past century, but the difficulties encountered in entirely ex- tracting the water and the inefficient me- chanical means then available were such > that the attempts toward producing powdered milk were perforcedly aband- -oned, and the production of the milk in a condensed form perfected. In this pro- cess the milk is converted into a thick liquid which, especially in the presence of cane or beet sugar, has keeping qualities sufficient to render it an article of com- merce easily transportable. But although the milk is considerably decreased in bulk by the process of condensing, explora- tion in the tropics, and long sea and land - expeditions, when all requisite food sup- plies have to be carried from the very start, rendered it apparent that a fur- ther diminution in the bulk was desir- able, not only in regard to weight but also in order to obtain a better keeping quality, since it is imperative with the con- densed product that the can in which it is carried should be absolutely airtight. Furthermore, condensed milk is some- what monotonous as a daily food owing to its extreme sweetness. Consequently the old question of reducing the fresh THe MarRINE REVIEW milk to a dry powdered form again im- pressed itself upon scientists, and numer- ous experiments to overcome the ob- stacles which had proved insurmountable to the pioneers in this direction were carried out, among them being Dr. Eken- berg's. In these renewed efforts the investigat- ors were appreciably assisted by the en- tire revolution that had taken place in the dairy industry by the introduction of the centrifugal skimming or separating ma- chine, which rendered the practical utiliz- ation of the resultant skimmed milk a question of vital importance, since the milk, being deprived of the greater pro- portion of the cream, was rendered un- marketable in the usual manner, so that it became somewhat of a by or waste pre- duct. But at the same time, although the separator made it possible for inland dairies, whence transportation of the raw fresh liquid was difficult. to produce a sal- able and remunerative article in the forin of butter, yet the bulk of the milk--skitn- med milk--containing the most valuable parts from a physiological point of view, was left behind. The operation of extracting the water and converting the milk into a powder appears at first sight to be somewhat simple, but in such a process care must be observed that the resultant product has none of its original and valuable properties destroyed or impaired. The powder generally known as "dry mitk," although made from milk, is in reality no longer milk, nor can it be re-converted into milk, though owing. to its nutri- tious value it is used extensively as an elergency food. In the Ekenberg pro- cess, however, the powdered milk, as it is termed, is actually dry milk easily solu- ble in water, and which, when recon- structed into its liquid form by the cor- rect proportionate addition of water, be- comes in every way similar to the original substance. Dr. Ekenberg discovered his process in 1899, but during the ensuing years many important improvements have been effected whereby the cost of produc- ing the powder is now quite nominal, so that the product can compete commer- cially with either the fresh or condensed milk, The feature of the Ekenberg process is that the heavy percentage of water pres- ent in the fresh separated liquid is rapidly evaporated at a low temperature under vacuum, the temperature at no stage of the operations being much higher than luke-warm. Upon arrival at the factory, the cans of milk are emptied into a small reservoir on the ground floor and then pumped to the receiving tanks located in the floors above. In Sweden, owing to regulations concerning milk, it is pasteur- ized at the dairies before being dispatch- ed to market, so that at the milk factory this preliminary process is avoided. In other countries, however, where such regulations do not obtain, pasteurization is carried out before the elimination of the water is proceeded with. All empty cans are carefully and thoroughly sterij- ized with steam before being returned to the dairies. The milk is first filtered through a cotton medium whereby all foreign substances in suspension are ar- rested. It is then cooled by means of refrigerators to a point just above freez- ing and is kept at this temperature dur- ing the day's work. ; The process of converting milk into powder consists in quickly drying the milk at the temperature of the blood or approximately 100 deg. F, For this operation a specially constructed appar- atus evolved by the inventor and known as the "Exsiccator" (milk dryer) is util- ized. In the majority of processes for extracting the water the milk is passed over or between rollers heated to a very high temperature, the powder being de- posited upon the external surface of the rollers, from which it is subsequently re- moved by scraping devices. In the Eken- - berg system the powder is deposited upon the inner face of a vacuum vessel. The exsiccator comprises a large, horizontal, cylindrical drum. which is caused to re- volve. The internal face of this drum is of nickel, which has been proved to be the most suitable metal for the purpose. The milk enters the exsiccator depart- ment through a floor standpipe, to. which flexible pipes extend from each exsicca- tor, it being possible to provide as many supply pipes from this central source as there. are machines for drying the milk. The supply is maintained by gravitation, the capacious tanks containing the raw milk being placed at suitable points above. The heating medium employed for evap- orating the milk is exhaust steam, which is. admitted to the interior of the drum when closed. In order to obtain high efficiency and rapid treatment the ends of the drum form bowls, dished outward. in which evaporation of the water to an extent of about four-fifths of the original amount takes place; here an evaporation effect of 160 to 180 kilogram- mes per hour per square meter (295 to 330 pounds per square yard) is obtained, which is a higher result than has hitherto been possible, since a locomotive boiler, for instance, evaporates only 40 kilo- grammes and a sugar vacuum from 60 and 80 to 100 kilogrammes per hour per square meter. This high evaporating efficiency is obtained by mainta'ning the milk in constant circulation. The solids of the liquid are deposited upon the nickel surface of the drum and are removed by means of German s'lver knives and de- posited in a special receptacle close to the drum, this vessel being arranged for a periodic discharge of its contents either by hand or by a mechanical device. Upon