SCIENCE AND INDUSTRY. 
systems employ pnactically one of two methods, viz.:—(1) Delivering 
the milk in a very thin sheet over the surface of a revolving heated 
roller. The size of these and the temperature used are suflicient to_ 
dry the milk before one revolution is complete, and the dried powder 
is scraped off the roller and finely ground. The Passburg system 
combines a preliminary concentration in a vacuum pan, followed by 
spreading on a roller. (2) Spraying the milk through a fine nozzle 
into a-heated chamber, with some provision for removing the moisture, 
e.g., by using a current of air. In the Campbell system a drying warm 
air is blown through the milk until it becomes thick. The milk is then 
exposed to the hot air by being dropped through it on to heated drums, 
where it is ground to fine powder. 
The Merrell-Soule process was introduced into America in, 1905, 
by the purchase of the German patent (1901) of Robert Stauf. This 
was the first of the spray processes, and the claim of the patent is as 
follows:—“ The process of obtaining the-solid constituents of milk in 
the form of powder, by converting the liquid into a fine spray, bring- 
ing such spray or atomized liquid into a regulated current of heated 
air, so that the liquid constituents are completely vaporized, conveying 
the dry powder into a suitable collecting space away fromthe air 
current and discharging the air, a vapour, separately from the dry 
powder”? The Merrell-Soule Company patented in 1907 the»further 
economical step of combining-a preliminary condensing in a vacuum 
pan. hes : 
This process is adaptable to drying a great variety of milk products. 
One of the great difficulties that had to be overcome was the develop- 
ment of raneidity; now the powders will keep well for six months to 
a year, and even milks up to 18 per cent. cream are successfully dried. 
There are many powders on the market, however, that do not keep 
well, and as the public generally does not discriminate as to the process, 
or even the brand, the whole industry suffers. Trufoods Ltd. have 
purchased the sole rights of the Merrell-Soule process for Australia, 
and salso control the sale of milk powders in England.’ The Merrell- 
Soulé system, however, is not the only one using the spray method. 
There are many others which differ chiefly in the nature of the nozzles 
used, the nature of the chamber, and the manner of removing moisture 
and collecting the products. 
Buttermilk, which either went to waste or was fed to pigs and 
calves previously, is now successfully dried to a powder. Apparently 
Victoria has led the way in this matter, though in most work in 
connexion with the preparation of milk powders, condensed milk, and 
the pasteurization of cream, New Zealand has been in the van. Butter- 
milk powder can be used to advantage by confectioners, bakers, and 
pastrycooks. It contains a high percentage of lactic acid, and a con- 
siderable amount of butter fat. Both of these add to its’ value in 
baking. The milk powder prepared by the spray system has been 
realizing 10d. a Ib. in the United States of America, while the powder 
from the heated rollers was being sold at 7d. , ; 
The rapidity with which the evaporation takes place in the spray 
method apparently is most advantageous. In accordance with physical 
laws the evaporation of a liquid uses up heat, and the milk solids are 
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