milk processing clarification pasteurization homogenization

1. B.AmeenaBeebi
Assistant ProfessorofHomeScience
VVVanniaperumalCollegeforWomen
Virudhunagar

2.  Processing helps to produce milk that has
initial low bacterial count,good flavour and
satisfactory keeping qualities.
 There are three operations of milk processing
and they are clarification , pasteurisation and
homogenation.

3.  Milk is passed through a centrifugal clarifier.
 The speed is adjusted in such way that cream is
not separated but dirt, filth and cells from the
udder and some bacteria are removed.
 The clarified milk is ready for pasteurisation.

4.  Pasteurisation derives its name from the French
scientist Louis Pasteur.
 Heating of certain liquids to a high temperature
which improved their keeping quality.
 Pasteurisation is the heating of milk to a
temperature which destroys organisms responsible
for tuberculosis and fever and other microbes
present in the product without affecting the
composition and properties of product.
 It also inactivates some of the natural enzymes like
lipase.

5.  Holding or Batch system
 High Temperature Short Time Method
(HTST)or the continuous system
 Ulta High Temperature System (UHTS).

6.  The holding system consists in bringing the milk
or cream to a temperature usually
65◦c and holding at that point for at least 30
minutes followed by rapid cooling.
 A higher temperature is sometimes used in which
case the time of holding may be shortened.
 In most recent years it is found that the organisms
causing Q fever, coxiella burnetti is more resistant
than tuberculosis organism and required a
treatment of 63◦c for 30 minutes to ensure its
destruction.

7.  The machine used are so constructed as to
make possible continuous operation and for
this reason of the system is called as flash
pasteuriser.
 This system depends upon the raising of the
temperature of the milk atleast 72◦c for 15
minutes as it passes through machine and
quick cooling.
 This does not impart cooking flavour and
cream line is not affected.

8.  This UHTSsystem results in a complete
pasteurisation of milk.
 In this method the milk is held for 3 seconds at
93.4◦c or for one second at 149.5◦c.
 After pasteurisation the milk is cooled rapidly
to 7◦c or lower.
 Pasteurised milk is not sterile. It must be
quickly cooled following pasteurisation to
prevent multiplication of surviving bacteria.

9.  The process of making a stable emulsion of
milk fat and milk serum by mechanical
treatment and rendering the mixture
homogeneous is homogenisation.
 Milk and cream have fat globules vary from 0.1
to 20µm in diameter. Homogenised milk fat
globules size is 2µm.
 The fat globules have a tendency to gather into
clumps.
 Homogenisation is done before pasteurisation.