All-E-β-carotene was dissolved in acetone and added to corn oil in
order to obtain a concentration of 300 μg/g±0.5 μg. The fortified
sample was sonicated for 1 min and then kept for one hour under
nitrogen in a glass bottle. A sample of 4 g of corn oil was added to the
reaction vessel and oxidized using the Rancimat Metrohm model 679
(Metrohm AG, Switzerland). Other conditions of Rancimat were air
flow of 20 L/h, and temperature of 110 °C. The samples were oxidized
for 1 to 14 h. After the experiment 400 μL of BHT (0.5% in methanol or
acetone) was added to the oxidized samples in order to stop further
possible reactions and to avoid formation of artifacts. A control sample
was also oxidized under similar conditions without β-carotene. The
oxidized samples were stored at −20 °C till analysis. All preparations
were carried out under nitrogen ambient environment and in the day
light.