Concentration effect of OOE in stripped SBO
Higher antioxidant concentrations do not necessarily provide greater antioxidant activity. In some cases, a higher concentration can result in a worse protection of oil. For example, it is well known that α-tocopherol exhibits pro-oxidant activity at highe concentrations (Huang et al., 1994). Another example is that 0.2 g/L and 0.25 g/L ethanol extract of Osage orange fruit did not show stronger antioxidant activity than 0.1 g/L in linoleic acid emulsion when monitored by a β-carotene discoloration method (Budincevic & Vrbaski, 1991). Therefore, a lower (0.05%) and higher (0.2%) concentration of OOE in SBO were compared with 0.1% OOE to determine the most effective concentration range of OOE.
As shown in Table 2, PV slightly lowered by increasing concentration of OOE from 0.05% to 0.2% at 25 ℃. However, CDV slightly increased andp -AV did not show a significant change with increasing concentration of OOE from 0.05 to 0.2%. At 40 ℃, PV slightly increased while CDV slightly decreased with increasing concentration of OOE from 0.05-0.2%. Although p -AV seemed to increase with increasing concentration of OOE, the difference was not statistically significant. Therefore, at both temperatures (25 and 40 ℃), the activity of OOE at 0.05, 0.1 and 0.2% did not seem to be very different. This indicates that the protection of SBO from oxidation at 25 and 40 ℃ can be achieved at a concentration as low as 0.05% OOE.