Regulation (EC) No. 2568/91 describes several analytical tests to be

used to check the quality of these oils. Among these is the gas chromato-
graphic determination of stigmastadiene (ethylcholestadiene) which is

an important indicator of the presence of refined oils in virgin oils. Many

vegetable oils are refined by steps including bleaching and deodoriza-
tion, which include treatment with acid bleaching earths and steam

treatment at high temperature. These processes dehydrate the ste-
rols present in the oil to form a series of steroidal hydrocarbons or

sterenes (Cert, Lanzón, Carelli, Albi, & Amelotti, 1994). The major

plant sterol is the β-sitosterol from principally 24-ethylcholesta-

3,5-diene (stigmasta-3,5-diene; Fig. 1) and lesser quantities of positional

isomers. Other sterols form similar compounds, 24-methylcholesta-

3,5-diene (campesta-3,5-diene) is formed from campesterol and

24-ethylcholesta-3,5,22-triene (stigmasta-3,5,22-triene) is formed

from stigmasterol.

The Regulation defines EVOO as having less than 0.15 mg kg−1 of

‘stigmastadiene’, which comprises the sum of stigmasta-3,5-diene and

an un-named isomer that elutes close to the -3,5-diene using the spec-
ified chromatographic conditions.



搶先評價 “stigmasta-3,5-diene”

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