From Milk to Dairy Products 5
1.1.1.1.
Composition and characteristics of milk fat
Table 1.1 shows the average lipid composition of cow’s milk.
Triacylglycerols represent approximately 97.5% of the total lipids.
Diacylglycerols, monoacylglycerols and free fatty acids are naturally present
in small amounts but their proportion can increase with lipolysis. The many
other compounds (cholesterol,
steroid hormones, vitamins, flavorings and
flavor substrates, etc.), even though low in number, play a crucial nutritional
and sensory role.
Class of lipids
Percentage of total lipids (w/w)
Triacylglycerols
97.5
Diacylglycerols
0.36
Monoacylglycerols
0.027
Free
fatty acids
0.1
Cholesterol
0.31
Hydrocarbons
Traces
Carotenoids
0.008
Phospholipids
0.6
Table 1.1.
Average lipid composition
of cow’s milk (Source: [CHR 95])
Milk triacylglycerols are made up of more than 400
different fatty acids,
which makes milk fat a very complex lipid source, as each fatty acid can be
esterified to one of the three hydroxyl groups of glycerol (Table 1.2).
However, only 12 fatty acids are present in quantities of more than 1%
(mol/mol). Fatty acids are either synthesized in the secretory cells in the udder
or taken from the bloodstream (body fat or food origin). Thus, milk fat varies
depending on the season, the cow’s diet and the
energy level of the food
intake, which could determine the ratio of
de novo
synthesis
with regard to
plasma uptake.
6 Handbook of Food Science and Technology 3
Fatty acids Symbol % mol
Distribution on the glycerol sites (% mol)
Melting point (°C)
Sn1 Sn2 Sn3
Butyric
4:0
4.8
-
-
35.4
-7.9
Caproic
6:0
2.2
-
0.9
12.9
-1.5
Caprylic
8:0
1.3
1.4
0.7
3.6
+16.5
Capric
10:0
2.9
1.9
3.0
6.2
+31.4
Lauric
12:0
3.3
4.9
6.2
0.6
+43.6
Myristic
14:0
10.8
9.7
17.5
6.4
+53.8
Palmitic
16:0
26.1
34.0
32.3
5.4
+62.6
Palmitoleic 16:1
1.4
2.8
3.6
1.4
-0.5
Stearic
18:0
10.8
10.3
9.5
1.2
+69.3
Oleic
18:1
24.1
30.0
18.9
23.1
+14.0
Linoleic
18:2
2.4
1.7
2.5
2.3
-5.0
Linolenic
18:3
1.1
-
-
-
-11.0
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