MILK FATS
Milk fats of mammals generally differ radically from the fat depots. The
greatest differences are seen at the level of the short and medium chain fatty
acids (from 4 to 12 carbon atoms) and about 3% butyric acid (C4:0).
If the fat content of milk is not very high (1.3% in horse, about 4% in cow,
goat, camel or human, 7.5% in sheep), fats account for approximately one third
of the dry matter.
In total, roughly 20 million tons of milk fats are produced per year, 85% being
from cows leading to about 6.5 million tons of butter (2004-05).
Milk fats are the most complex dietary fats. It was reported that dairy fat
contains about 40 major fatty acids but a total of about 400 minor ones have
been detected (Jensen R G, J Dairy Sci 2002, 85, 295). A unique feature
of dairy fat is the occurrence of trans fatty acids (vaccenic
and rumenic acids). The archaeological
presence of milk in preserved sites may be asserted in determining the stable
carbon isotope (d13C)
compositions of individual fatty acids siince milk and adipose fat from animals
raised on similar pastures have distinct isotopic signatures (Evershed RP et
al., Acc Chem Res 2002, 35, 660).
The average fatty acid compositions (weight percent) of six important milk
fats are given in the table below:
| Cow | Ewe | Goat | Donkey | Horse | Human | |
| 4:0 | 2.9 | 10.3 | 2.2 | 2.1 | 0.6 | 0.6 |
| 6:0 | 0 | 3.4 | 2.5 | 0.5 | 0.5 | 0.1 |
| 8:0 | 0.6 | 2.5 | 2.8 | 4.1 | 2.1 | 0.1 |
| 10:0 | 2.1 | 6.1 | 10 | 9.5 | 5 | 0.6 |
| 12:0 | 2.6 | 3 | 4.7 | 8.9 | 5 | 4.1 |
| 14:0 | 9.4 | 7 | 11.7 | 7.5 | 6.5 | 7.3 |
| 16:0 | 24.1 | 19.8 | 28.8 | 20.9 | 15.3 | 25.6 |
| 16:1 | 2.6 | 0.7 | - | 5.4 | 6.8 | 0.1 |
| 18:0 | 10.9 | 11.8 | 7.5 | 1.5 | 2.5 | 7.9 |
| 18:1 | 28.2 | 22.8 | 17.1 | 19.8 | 18.2 | 26.8 |
| 18:2 | 2.1 | 2.7 | 3 | 9 | 6.5 | 10.9 |
| 18:3 | 0 | 0.8 | 0.3 | 5.1 | 15.9 | 0.5 |
It must be noticed that milk from
ruminant animals (cow, buffalo, goat, ewe,
camel...)
contains butyric acid (4:0), in contrast to others (man, horse, donkey) which lack this
fatty acid produced by the bacterial hydrogenation in stomach.
The fatty acid composition of milk fats is under the influence of the diet but
the positional distribution of fatty acids is not. The location of the short
chain acids appears restricted to the position 3 and only one short chain can
occur per molecule.
Human milkfat substitute has been developed from vegetable oils (Betapol
from Loders Croklaan). The product has a structure similar to human milkfat,
matching its fatty acid composition and fatty acid distribution (about 70% of
palmitic acid at the sn-2 position). Betapol production involves
position-targeted reactions catalyzed by 1,3-specific lipases.
Specific distribution and association
of the fatty acids can be deduced from the table given below:
|
sn |
4:0 |
6:0 |
8:0 |
10:0 |
12:0 |
14:0 |
16:0 |
16:1 |
18:0 |
18:1 |
18:2 |
18:3 |
20:1 |
20:4 |
|
Man |
1 2 3 |
0.2 0.2 1.8 |
1.3 2.1 6.1 |
3.2 7.3 7.1 |
16.1 58.2 6.2 |
3.6 4.7 7.3 |
15.0 3.3 2.0 |
46.1 12.7 49.7 |
11.0 7.3 2.0 |
0.4 0.6 1.6 |
1.5 0.7 0.5 |
0.9 0.3 |
|||
Ewe |
1 2 3 |
1.9 0.3 31.7 |
0.3 2.6 8.4 |
0.9 0.2 7 |
3.1 2.7 14.2 |
2.8 3.9 3.2 |
8 11.6 3.4 |
35.5 27.2 2.6 |
0.9 1.3 0.4 |
17.3 14.6 7 |
25.7 30.9 18.8 |
2.6 4.0 2.4 |
1 0.8 0.9 |
||
| Donkey | 1 2 3 |
1 0.6 2.5 |
0.3 0.4 1 |
0.9 0.9 9.2 |
3.6 2.7 28.5 |
6.1 8.2 8.3 |
8 13.4 6.2 |
23.2 26.9 2.1 |
10.7 11.3 3.9 |
3 2.3 1.6 |
19.2 14.4 13.2 |
13.7 9.7 10 |
6.8 4.2 4.1 |
||
|
|
1 2 3 |
1.4 0.2 15.9 |
0.4 0.7 8.6 |
0.7 0.1 10.6 |
4.9 2.2 30.2 |
3.3 5.9 3.4 |
9 9 18.6 |
38.4 35.7 1.4 |
0.5 0.8 0.2 |
17.6 12 7.1 |
21.7 21.1 19.2 |
0.7 2.2 1.6 |
0.5 0.4 0.6 |
||
Cow |
1 2 3 |
5.0 2.9 43.3 |
3.0 4.8 10.8 |
0.9 2.3 2.2 |
2.5 6.1 3.6 |
3.1 6.0 3.5 |
10.5 20.4 7.1 |
35.9 32.8 10.1 |
2.9 2.1 0.9 |
14.7 6.4 4.0 |
20.6 13.7 14.9 |
1.2 2.5 0.5 |
(Data for ewe, goat and donkey are from Blasi F et al., J Food Comp
Anal 2008, 21, 1)
