44 Chapter 2
affects the safety of milk. Mastitis (severe
infl ammation of the udder due to pathogenic
microorganisms) is the primary disease that
contributes to variations in milk composition
and milk yield. Consequently, dramatic
losses in milk yield and very high counts of
lymphocytes occur.Processing
The processing of milk includes agitation,
mixing, and cooling at the farm; clarifi cation,
separation, and standardization; pasteuriza-
tion; homogenization; packaging and distri-
bution; followed by sanitation of the
processing area. Clarifi cation involves cen-
trifugation to remove somatic cells, bacteria,
and sediment from the milk. Next, cream is
separated from skim milk via centrifugation
followed by pasteurization (usually 72 ° C for
15 seconds), which destroys pathogens and
other microorganisms. Homogenization is
the mechanical process of shearing fat glob-
ules via pressure reducing the size of the fat
globules and reducing the separation of the
cream portion of the product.
The many factors that infl uence milk com-
position are eliminated by standardization,
which is a processing requirement.
The composition of organic milk may
vary from conventional milk because organic
processing avoids the use of synthetic fertil-
izers, pesticides, growth promoters, or addi-
tives. Furthermore, organically certifi ed milk
does not use any ingredients, additives, or
processing aids derived from genetically
modifi ed organisms (GMOs). The organic
industry strictly forbids the use of ammo-
nium, bleach, and hypochlorite products
for the cleaning of processing areas and
equipment. The products used should be
biodegradable, have low toxicity, and not
contaminate the environment. Several studies
comparing organic and conventional milk
have shown that lipid composition of organic
and conventional milk are signifi cantly dif-
ferent. The conjugated linoleic acids and
omega - 3 fatty acids, in particular, were sig-milk. Overall, the infl uence of diet on protein
and lactose content in the milk has been
minimal. Seasonal and regional changes have
been shown to infl uence changes in diet,
especially severe heat. However, generally
slight but well - defi ned variations are present
in both the fat and solids - not - fat components
of milk over the course of a year.
Comparisons between concentrate - fed
and pasture - fed milk animals, including goats
and sheep, showed that different feeds
affected the composition. Higher levels of
conjugated linoleic acids (CLAs) and poly-
unsaturated fatty acids (PUFAs) were present
in the milk of pasture - fed cows, goats, and
sheep (Morand - Fehr et al., 2007 ).
Stage of Lactation
The lactation stage of the cow infl uences the
milk yield and the concentrations of lactose,
fat, and protein in milk. Lactose and fat con-
centrations increase as lactation progresses.
Milking Frequency
The frequency and completeness of milking
affects milk yield and milk composition.
Shorter times between milking have resulted
in poor milk yield and higher fat content.
Location
The composition of milk is affected by the
location of cows. In particular, farming man-
agement practices infl uence the composition
of milk. For example, comparisons between
conventional and organically farmed cow ’ s
milk have shown signifi cant differences in
the compositions of fatty acids (Bloskma
et al. 2008 ). The location also infl uences the
feed given to the cows, and this affects the
overall composition of milk.
Disease Status
The disease status of the animal contributes
greatly to a variable composition, and also