R. Borquez et al., A RAPID METHOD TO DETERMINE THE OXIDATION-KINETICS OF N-3 FATTY-ACIDSIN FISH-OIL, Lebensmittel-Wissenschaft + Technologie, 30(5), 1997, pp. 502-507
The resistance of unsaturated fatty acids against oxidation was determ
ined by monitoring gas chromatographically changes in three n-3 fatty
acids (octadecatetraenoic (C18:4n-3), eicosapentaenoic (C20:5n-3) and
docosahexaenoic acid (C22:6n-3)) in mackerel oil that had been exposed
to temperatures of 80, 90 and 100 degrees C to accelerate oxidation.
Fatty acids contained in the oils were converted into methylesters by
reaction with trimethylsulfoniumhydroxide taking place immediately in
the injection parr of the gas chromatograph. Results were expressed as
weights fractions of C18:4n-3, C20:5n-3 and C22:6n-3 by comparison to
an internal standard (methyl tricosanoate ester, C23:0). The repeatab
ility values (r) obtained for the GC method used in this study were 2.
90 mg/g oil, 1.49 mg/g oil and 2.31 mg/g oil for C18:4n-3, C20:5n-3 an
d C22:6n-3, respectively. A brief thermal pretreatment of the oil-trim
ethylsulfoniumhydroxide solution, or using a trimethylsulfoniumhydroxi
de/oil fraction above the stoichometric relation did not influence the
results, i.e. the concentration of n-3 fatty acids obtained The oxida
tion reactions kinetics were modelled in terms of the hydroperoxide fo
rmation mechanisms from unsaturated fatty acids.