Dairy Processing - November/December 2022 - 57

EQUIPMENT
Working with
gravity
by Michael Gordon | dairyprocessing@sosland.com
A
milk and cream separator is an important piece of
industrial equipment that uses centrifugal force to
remove cream from whole milk.
Today's milk centrifugation technology helps companies
produce the cleanest creams, milks, cheeses and powders,
all while increasing production, improving consistency and
reducing waste. Such separation is possible because milk and
cream naturally like to separate.
WHERE IT STARTED
In the big picture, the centrifugal separator is a recent invention.
For centuries, the technique for separating one substance from
another was the natural process of sedimentation by gravity.
Sedimentation by gravity was also the original technique
used in dairying to separate fat from milk. Milk fresh from the
cow was left in a vessel and after some time the fat globules
aggregated and floated to the surface where they formed a
layer of cream on top of the milk that was then skimmed off
by hand.
Just as gravity acts to naturally separate the milk and the
cream, cream separators do the same thing - but much more
quickly. Cream separators utilize centrifugal force by feeding the
raw milk into a central spinning chamber.
Within this chamber are conical disk stacks that rotate in
a drum, creating centrifugal force thousands of times stronger
than gravity. The fat within the milk stays within the center of the
drum, and the heavier skimmed milk is pushed to the edges.
Cream separators guarantee milk fat consistency and can
also be modified to assist with clarification and the removal of
foreign objects and pathogens.
MILK CLARIFICATION
Clarification of raw milk and whey as they arrive at the dairy
removes biological impurities such as cells and blood from
milk, strips out any remaining cheese fines from whey, and
56 NOV-DEC 2022 | DAIRYPROCESSING.COM
clears liquid ingredients of any dirt and dust from the dairy or
transportation.
In many cases, milk must be clarified on reception of the
dairy to remove particles of dirt and somatic cells such as
Leucocyte. This will reduce the presence of listeria which is
trapped inside the leucocyte. While the milk clarifier can operate
with cold or warm milk, clarification efficiency improves at
higher temperatures. Centrifuges for milk separation - or
skimming -- also perform clarification, but their efficiency is low
compared with milk clarifiers.
High-speed disc stack centrifuges play three key roles in
standardized milk production including clarification to remove
foreign matter such as hair, stray cow cells and dirt. They also
aid in purification, pulling the butterfat from the raw milk in
order to produce skim milk and cream, and standardization,
which regulates the fat content of finished milk by blending some
cream back in, producing 1% milk, 2% milk or half-and-half.
These centrifugal separation operations give milk producers
a lot of control, allowing them to ensure the safety of their
products while increasing yields and controlling the quality.
WARM VS. COLD MILK SKIMMING
Raw milk and whey undergo both pasteurization and cream
separation prior to use as the basis for milk powder products.
Separating the cream to generate non-fat milk can be carried
out using either a warm milk separation process or a cold
milk process. Using the cold process makes it possible for the
resulting skim milk to be used as the basis for products such as
low heat formulas.
Milk skimming during pasteurization is the most common
centrifugal separator application in dairies. The product
temperature should normally be kept between 113°F and 131°F,
in order to ensure optimal skimming efficiency.
Cold milk separation at greater than 39.2 °F takes place
in a number of processes including cheese making using
Separators guarantee milk fat consistency and
can assist with removal of foreign objects.
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Dairy Processing - November/December 2022

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