UNSWEETENED CONDENSED Mink Directs 255 
known fact, established by practical experience in processing. 
and by analyses of different brands of evaporated milk, that in 
some European countries, milk can be condensed to a much 
higher degree of concentration than in most seetions of this 
country, without becoming permanently curdy. 
Effect of Forewarming or Preheating on Curdling.—As ex- 
plained in Chapter XI on “Sterilizing.” under “Factors that 
Decrease Viscosity of Evaporated Milk. the readiness with 
which milk coagulates in the sterilizer is diminished by lengthen- 
ing the period of preheating in the forewarmer, or by raising the 
temperature of preheating, or both. And vice versa, the shorter 
he temperature (below 
the period of preheating and the lower t 
216 degrees F°.) to which the milk is forewarmed, other conditions 
being the same, the greater the danger of curdling in the steril- 
IZer. 
It is not improbable that here again the modification of the 
balance of the calcium and magnesium with the phosphates and 
citrates, may be the tundamental cause of these phenomena. 
In this case the longer exposure to the forewarming heat, or the 
higher temperature of forewarming, or both, may have the effect 
of lowering the soluble calcium content by precipitating part of 
it as insoluble calcium phosphate. Tf coagulation is due to an 
excess of calcium or magnesium, as it usually is, then this lower- 
ing of the calcium content, as the result of preheating, will mini- 
mize the danger of coagulation in the sterilizer. 
Effect of Addition of Water on Curdling.—Addition of ex- 
traneous water to the evaporated milk lessens the intensity of 
coagulation in the sterilizer. ‘This is a matter pretty generally 
understood by the experienced operator, as pointed out in Chapter 
XI on “Sterilizing” under “Factors which Decrease Viscosity 
and Tendency to Curdle.” It is due to the dilution of both the 
casein and the serum in milk. 
Effect of Concentration.—The more concentrated the evap- 
orated milk, the greater the danger of lumpiness. All the con- 
ditions causing lumpiness are intensified by the degree of con- 
eentration.!. The manufacturer must, therefore, study the be- 
: 1¥For detailed discussion of relation of quality of fresh milk to curdiness 
of evaporated milk see Chapter VIII on ‘Manufacture of Evaporated Milk," 
“Quality of Fresh Milk.” 
