Principles of Cheese Technology 233The composition of a cheese variety deter-
mines whether milk should be adjusted for
the protein:fat ratio. Predominantly, the
casein:fat ratio of the starting milk deter-
mines the fat:protein ratio of cheese. A
fat:casein ratio of 1.47 is generally consid-
ered optimum for cheddar cheese. Assuming
a casein level at 2.2%, an optimal fat level of
3.2% in milk is desirable for making cheddar
cheese. Different ratios are needed for other
cheese varieties. For example, for mozzarella
cheese, milk must be standardized to 1% to
3% fat, depending on the type of mozzarella.
Part - skim mozzarella is made from 1% to 2%
fat (0.37 : 0.75 fat : casein ratio), whereas
regular mozzarella is made from 3% milk
(fat:casein ratio of 1.11).
It is essential to standardize cheese
milk to a specifi c fat content to achieve a
specifi c fat:casein ratio in cheese. Various
automated milk standardization instruments
are being used in the cheese industry. Milk
analyzers based on near infrared technology
are among the techniques gaining popu-
larity. These techniques improve production
effi ciency as well as the quality and consis-
tency of the fi nal product (Barbano and
Lynch, 2006 ). Cheese milk can be standard-
ized by one of the following methods dis-
cussed below.Separator
Fat content in raw milk may be reduced
and standardized by running milk through a
separator, which partially or totally removes
fat to achieve a desired level for a spe-
cifi c cheese. For example, partial removal
of fat is required for part - skim mozzarella,
and skim milk is needed for cottage cheese
manufacture.Addition of Skim Milk
The amount of skim milk to be added for
reducing fat content of cheese milk is calcu-
lated as follows:cow ’ s milk, which makes it coagulate more
easily. Because the fat in goat ’ s milk contains
smaller fat globules, the fat breakdown by
lipases is accelerated. Fat recovery is higher
and the curd possesses a smoother texture.
Milk for cottage cheese manufacture must
conform to Grade A requirements (USDHHS,
FDA 2003 ). In general, all milk supplied for
cheese making should be of excellent micro-
biological quality. Due to bacterial growth,
protein in milk may be degraded to soluble
end products, thereby reducing the protein
available for retention in cheese. Furthermore,
microbial activity generates various off
fl avors in milk, which are carried into cheese
and affect its quality. Most of the cheese
made in the United States originates from
pasteurized milk. It is generally accepted that
cheese made from raw milk must be aged for
at least 60 days to ensure safety from patho-
genic infection.
Treatment and Standardization
of Milk
Several approaches are used to remove the
extraneous particles of raw milk. Raw milk
may be passed through cloth fi lters or run
through clarifi ers to remove denser particles.
If milk is run through a separator to remove
part or all of the fat, heavier particles are
collected in the bowl as sludge, while cream
and skim milk streams fl ow out of the separa-
tor. Bactofugation is a high - speed centrifugal
process that removes all bacterial cells and
95% of spores. It drastically reduces late gas
defects in cheese caused by Clostridium tyro-
butyricum. This process fractionates heavy
casein particles, leucocytes, somatic cells,
bacterial cells, and spores in 1% to 2% of the
starting milk. For recovery, this fraction is
sterilized by ultra - high - heat treatment and is
subsequently added back to cheese milk. Some
plants use microfi ltration, which removes
99% of spores but can be used only for skim
milk. Microfi ltration membranes retain fat
globules along with bacteria and spores.