2009_Book_FoodChemistry

174 3 Lipids
Fig. 3.7. Composition of triacylglycerols present in edible fats or oils as determined by HPLC. a Olive oil,
b soybean oil, c sunflower oil, d wheat germ oil. Fatty acids: P palmitic, S stearic, O oleic, L linoleic, Ln linolenic,
Ao eicosanoic
Various hypotheses have been advanced,
supported by results of TG biosynthesis, to
predict the TG composition of a fat or oil
when all the fatty acids occurring in the
sample are known. The values calculated
with the aid of the 1,3-random-2-random
hypothesis agree well with values found experimentally
for plant oil or fat. The hypothesis
starts with two separated fatty acid pools. The
acids in both pools are randomly distributed and
used as such for TG biosynthesis. The primary
HO-groups (positions 1 and 3 of glycerol) from
the first pool are esterified, while the secondary
HO-group is esterified in the second pool. The
proportion of each TG is then determined (as
mole-%):
[ ] [ ] [ ]
mol-% × in mol-%Y in mol-%Z in
β-XYZ(mol-%) = 2 ·
·
·
· 10
1,3-Position 2-Position 1,3-Position
−4
(3.24)
The data required in order to apply the formula
are obtained as follows: after partial hydrolysis
of fat (oil) with pancreatic lipase (cf. 3.7.1.1), the