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.