182 QUEENSLAND AGRICULTURAL JOURNAL. [1 Maz., 1898. 
CONDENSING MILK BY COLD PROCESS. 
By BYRON F. McINTYRE, Ph.G. 
Rahway, New Jersey. 
‘CoxstvERING the wide and extended territory in which the concentrated forms 
-of milk are used, their dietetic value and methods of preparation cannot but 
be interesting to chemists and pharmacists; therefore additional notes are 
presented on the so-called cold process of condensation. 
The process may be briefly summarised as follows :— 
1. Reducing the bulk of the milk by conversion of the water of the 
milk into ice, instead of vapour or steam ; 
2. The making of the ice on the surface only of the milk, by elevation 
of the freezing-pans in an atmosphere of zero temperature or there- 
abouts; 
8. Frequent breaking of the surface ice, so that fresh liquid is pre- 
sented to a freezing effect, with gradual submersion of the broken 
ice as the bulk of ice increases ; 
4. Standardisation of the product. 
An experimental application of the process was made in Cattaraugus, New 
York, under favourable refrigerating conditions, and with milk of exceptional 
milk fat strength. The dairy product of this section had been cheese, and, 
while there were strains of registered stock in the dairies, there had been little 
observance of the proper conditions of cleanliness of stables, feeding of the 
‘stock, and care of milk as found in the better class of eastern dairies supplying 
milk for city delivery. Considerable difficulty was experienced in the selection 
of milk free from “ cow odour.” Milk with perceptible taint of animal odour 
is unfit for condensation by cold process, as these odours are intensified by 
condensation. ‘To correct, in part, flavour defects in the milk, it was run into 
‘@ vacuum pan, and the pan and contents gently heated to 80° F., a vacuum of 
20 inches having been obtained. This treatment extracted animal gases and 
-atmospheric air dissolved in the milk, which were carried. to the surface in 
bubbles, increasing the apparent bulk of the milk about one-tenth. After a 
few minutes the foam broke up, and the milk became normal in bulk. The 
milk was then at the proper temperature for removal of milk fat by means of 
4 cream separator which was set to run heavy cream. This heavy cream should 
assay not less than 50 per cent. milk fat. One object in separating cream from 
the milk was to secure the extraction of dirt and foreign animal products, 
which were very much in evidence as a waste product adhering to the bowl cf 
of the separator. From the separator the fat-free milk was run over a bank 
of horizontal copper pipes through which ice water was circulated, reducing 
- the temperature of the milk from 80° F. to 35° F. A+ this point it should be 
noted that milk reduced by heat under vacuum conditions in the proportion of 
four parts of milk to one part of condensed milk will have a viscosity somewhat 
proportionate to the heat used in the process. In other words, heatin 
thickens the albuminoids of the milk very much as egg albumen is thickene 
by heating. ' 
In the cold process of condensing, there is no thickening or chemical 
change in the albuminoids, the density varying proportionately to the water. 
content, so that four parts of milk condensed by cold process does not haye the 
density or the quality of thickness as seen in commercial brands of unsweetened 
condensed milk. A condensation of five and one-half gallons to one gallon is 
required to produce a product with the desired consistence or thickness, which 
is an increase of over one-third in the fat-free milk solids as compared with a 
standard of four to one. Economically considered, this is unobjectionable, as the 
skim or fat-free milk has but little cash value, and the preparation has increased 
nutritive value in its nitrogenous constituents. 
