Storage experiments
OOE (0.1 wt.%), mixed tocopherols
(Toco, 0.1% wt.%), BHT (0.02 wt.%), or rosemary extract (RE, 0.1
wt.%) was weighed in an Erlenmeyer flask. Concentrations of OOE and
Toco were based on the content of osajin and pomiferin (72.9%) and the
content of total tocopherols (74.0%), respectively.
Since RE was a commercial product
containing other ingredients than antioxidants, the concentration of
active components was not known. The concentration of RE recommended by
the manufacturer was 0.02-0.1 wt.% in oil, and the maximum recommended
concentration (0.1%) was used in this study. Stripped SBO or FO was
added in the Erlenmeyer flask containing an antioxidant and stirred
under argon until the antioxidant dissolved. Oil (3.0 g) was transferred
to three vials (60 mm height, 26.2 mm i.d.) per treatment and per each
time point. For OOE, which was not completely dissolved, 3.0 g of
suspension of OOE in oil was transferred to vials while being stirred
with a magnetic bar under argon. This is an accelerated storage test due
to the relatively high surface area to volume ratio (1.65
cm2/cm3). Oil samples were stored at
25 ℃ and 40 ℃, removed at each time point, transferred to smaller vials
(45 mm height, 12 mm i.d.), and kept in a freezer (-20 ℃). PV was
measured within 24 h, and then other values were determined after PV.