2009_Book_FoodChemistry

234 3 Lipids
Fig. 3.45. Tocopherols and tocotrienols present in food
3.8.3.2 Analysis
Isolation of tocopherols is accompanied by losses
due to oxidation. Therefore, the edible oil is
dissolved in acetone at 20–25 ◦ C in the presence
of ascorbyl palmitate as an antioxidant. The
major portion of triacylglycerols is separated by
crystallization at −80 ◦ C. Tocopherols remaining
in solution are then analyzed by thin layer or gas
chromatography (after silylation of the phenolic
HO-group) or by HPLC (cf. Fig. 3.46). UV spectrophotometry
is also possible. However, the
fluorometric method based on an older colorimet-
ric procedure developed by Emmerie and Engel
is even more sensitive. It involves reduction of
the Fe (III) ion to Fe (II) by tocopherols and the
reaction of the reduced iron with 2,2 ′ -bipyridyl
to form an intensive red colored complex.
3.8.4 Carotenoids
Carotenoids are polyene hydrocarbons biosynthesized
from eight isoprene units (tetraterpenes)
and, correspondingly, have a 40-C skeleton.
Table 3.54. Tocopherols and Tocotrienols in plant oil a
Oil α-T α-T-3 β-T β-T-3 γ-T γ- T-3 ∂ -T ∂ -T-3
Sunflower 56.4 < 0.02 2.45 0.2 0.4 0.02 0.09
Peanut 14.1 < 0.02 0.4 0.4 13.1 0.03 0.92
Soya 17.9 < 0.02 2.8 0.4 60.4 0.08 37.1
Cottonseed 40.3 < 0.02 0.2 0.9 38.3 0.09 0.5
Corn 27.2 5.4 0.2 1.1 56.6 6.2 2.5
Olive 9.0 < 0.02 0.2 0.4 0.5 0.03 0.04
Palm (raw) 20.6 39.2 < 0.1 2.5 < 0.1 42.6 2.6 10.1
Wheat germ 133.0 < 2.6 71.0 18.1 26.0 27.1
Almond 20.7 0.3 0.9
Apricot kernel 0.5 22.4 0.3
Peach kernel 6.4 1.3 1.0
Cocoa butter 0.3 < 0.1 5.3 < 0.1
Palm oil, middle
fraction < 0.1 < 0.1 0.43 < 0.1
Shea fat stearin < 0.1 < 0.1 0.43 < 0.1
a Average composition; indicated in mg/100 g.