Dairy Ingredients for Food Processing

124 Chapter 5

vacuum pan method for manufacturing evap-

orated milk in England in 1835. In 1856, Gail

Borden received patents in the United States

and England for preserving milk in a semi -

fl uid state after evaporation in a vacuum,

leading to sweetened condensed milk in her-

matically sealed cans. In 1857 an English

patent was granted to Joseph House for pre-

serving unsweetened condensed milk.

However, the fi rst known commercial evapo-

rated milk was produced in 1885 in the

United States by the Helvetica Condensing

Milk Company in Highland, Illinois.

The application of homogenization in the

production of evaporated milk was intro-

duced in 1909 to stabilize the emulsion

and reduce fat separation. The continuous

system for sterilizing evaporated milk was

developed in 1922, and in 1923, the U.S.

Department of Agriculture promulgated an

advisory standard for condensed milk, evap-

orated milk, and concentrated milk. For more

on the historical developments and perspec-

tives, see Parfi tt (1956) and Bell (1962).

Types of Evaporated and

Sweetened Condensed Milks

Unsweetened and sweetened condensed milk

can be made from fresh milk or recombined

milk (nonfat dry milk, fat, and water). When

the source of fat is other than butterfat, the

resultant milk is called fi lled milk. The U.S.

Code of Federal Regulations (21CFR131 : 115)

defi nes concentrated, evaporated, and sweet-

ened condensed milk as follows:

“ Concentrated milk, also called condensed

milk, by defi nition is product obtained by

partial removal of water from milk. It con-

tains not less than 7.5% milk fat and not less

than 25.5% total milk solids. It is pasteurized

but not processed by heat to prevent spoilage

and it may be homogenized. Vitamin addition

is optional. If added, the quantity of Vitamin

D in each fl uid ounce is 25 IU. ”

Evaporated milk, also called unsweetened

evaporated milk, is about 2 times concen-

2. Increase in hygroscopicity.


3. Changes in salt equilibrium in milk
   (mainly due to increased Ca^2 +^ ion activ-
   ity leading to undissolved calcium phos-
   phate. Consequently, pH of concentrated
   milk decreases by 0.3 to 0.5 unit.


4. Conformational changes in proteins due
   to increased protein association and
   compaction.


5. Changes in physicochemical properties
   (i.e., osmotic pressure; freezing point
   depression; boiling point elevation;
   increase in electrical conductivity,
   density, and refractive index; and
   decrease in heat conductivity).


6. Increased viscosity, which is tempera-
   ture dependent.


7. Decrease in diffusion coeffi cient with
   moisture content.

Historical Perspective for

Evaporated and Condensed Milks

In the late 1700s Nicolas Appert was the fi rst
to develop the process to evaporate and pre-
serve milk in a sealed container in France to
meet the required need for the French army
to preserve food. Appert was awarded a
patent on January 30, 1810, for developing a
process for keeping milk for an extended
period. His process included boiling milk in
an open kettle to one - third of its original
volume, sealing it in an airtight bottle, and
reheating the sealed container and its con-
tents in a hot water bath. The reason behind
the preservation that resulted from Appert ’ s
method was later explained by the work of
Louis Pasteur, who demonstrated the nature
and behavior of microscopic organisms
during heat processing.
Further development by was reported in
an English patent awarded in 1813 to Edward
Howard, who described a vacuum pan
method for boiling milk vigorously at a low
temperature (54.4 ° C or 130 ° F) and removing
50% of its water content. This led to the