From Milk to Dairy Products 41
1.3.4.1.
Physicochemical and biological standardization of milk
The quality of milk for cheese production can be defined by its suitability
to form a coagulum resulting, after draining
and eventually ripening, in a
cheese with defined physicochemical properties and a satisfactory yield. Milk
has a varied composition depending on the animal species, breed, individual,
lactation stage and number, method and time of milking, season, climate, diet
and so forth. Not all milk has the same suitability for cheese production since
it differs in some characteristics such as casein content and composition, salt
balance, lactose content, hygienic quality, pH and so on. These characteristics
affect their ability to coagulate, which is necessary to pass from the liquid to
the solid state, as well as the properties of the coagulum.
In order to avoid variations in the protein content of milk and improve
coagulation
properties, which affect cheese yield and quality,
manufacturers
are able to adjust the milk protein level to between about 30 and 42 g L
-1
using
various techniques: removal of water by evaporation or reverse osmosis,
concentration by nanofiltration, ultrafiltration (most common), microfiltration
or the addition of caseinates.
In order to adjust the “fat/dry matter” ratio that is specific to each type of
cheese, manufacturers standardize the milk fat while
taking into account the
milk protein composition. Using a weight of standardized milk (w
SM
) in terms
of fat (F
SM
) and protein (P
SM
), and knowing the cheese yield and recovery
coefficients of these constituents in the cheese (see section 1.3.5.3), it is
possible to
obtain a weight of cheese w
C
with the desired characteristics
(fat content F
C
,
protein content P
C
; Figure 1.19).
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