Food Chemistry

232 3 Lipids

Gas chromatographic-mass spectrometric
studies have also revealed the presence of 4,4-
dimethylsterols in the steroid fraction of many
plant oils:

α-Amyrine (3.113a)

β-Amyrine (3.113b)

Cycloartenol (3.114)

Oleanolic acid (3.115)

Lup-20(29)-en-3β-ol (Lupeol) (3.116)

Fig. 3.43.Sterol detection according toLieberman–

Burchard.Reactions involved in color development

Oleanolic acid has long been known as a con-

stituent of olive oil. Methyl- and dimethylsterols

are important in identifying fats and oils

(cf. Fig. 3.44).

3.8.2.4 Analysis...............................................

Qualitative determination of sterols is conducted

using the Liebermann–Burchard reaction, in

which a mixture of glacial acetic and concen-

trated sulfuric acids reacts directly with the fat

or oil or the unsaponifiable fraction. Several

modifications of this basic assay have been

developed which, depending on the steroid

and the oxidizing agent used, result in the

production of a green or red color. The reaction

is more sensitive when the SO 3 oxidizing agent

is replaced by the Fe^3 + ion. The conversion

of sterols into a chromophore is based on the