Dairy Ingredients for Food Processing

Processing Principles of Dairy Ingredients 117

droplet. If this step does not occur, the fat

droplets could recombine to form a larger

globule. The adsorption time has been esti-

mated to be around 0.25 μ , the encounter time

between the protein and fat is estimated to be

015 μ , and the deformation time is around

0.3 μ for 4% fat milk being homogenized at

The results of homogenization are smaller
fat globule size (prevention of creaming),
whiter and more appetizing color, reduced
sensitivity to fat oxidation, and a fuller
bodied fl avor and mouth feel. In cultured
milk products a better stability is also
achieved. Homogenizers are high - pressure
machines in which reciprocating pistons
create the pressure. Pressurized milk is
passed through a narrow aperture. When the
pressurized milk exits into atmospheric pres-
sure, cavitation is created which results in
large fat globules being reduced to smaller
ones. The narrow aperture is called the
homogenizer valve. There are many designs
for the homogenizer valve, all of which have
a similar effect on the fat globule (Figure
4.15 ).
When a large fat globule is disintegrated
to a number of small droplets, a tremendous
increase in surface area of the fat occurs.
Onto the surfaces of these newly created
droplets casein adsorbs and stabilizes the

Figure 4.14. The homogenizer is a large, high - pressure pump with a homogenizing device. 1, main drive
motor; 2, V - belt transmission; 3, gear box; 4, damper; 5, hydraulic pressure setting system; 6, homogenizing
device 2nd stage; 7, homogenizing device 1st stage; 8, solid stainless steel pump block; 9, pistons; 10, crank-
case. Reproduced with permission from Tetra Pak.

1 2 3 4 5 6 7

8

9

10

Figure 4.15. The milk is forced through a narrow

gap which results in the fat globules splitting into

smaller sized droplets. Reproduced with permission

from Tetra Pak

Forcer

Homogenized Seat

product

Homogenized

product

Gap ≈ 0.1 mm