Antioxidant components and antioxidant capacity analysis
Tocopherol analysis was performed by HPLC as described previously using
Hitachi instruments equipped (Hitachi, Japan) with a C18–Varian column
(25 cm×4 mm; Kanto Chemical Co., Inc., Japan), and detection was applied
using a UV detector at 298 nm (Yang et al., 2017). The calibration
curves of each standard were initiated by plotting peak area versus the
corresponding concentration, respectively. Phytosterol analysis was
performed by GC/MS as described previously using Agilent instruments
equipped with a DB–1 column (60 m×0.25 mm i.d.; Agilent, Palo Alto, CA,
USA). The 5α–cholesterol was taken as an internal standard, and the
ratio of the peak area of the analyte and internal standard was used as
an analytical signal (Jun–Hua et al., 2008).
The total phenolic and total flavonoid contents were analyzed using the
method mentioned in previous literature (Yang et al., 2018). Each oil
sample (5g) was mixed with acetone/methanol (2:8) to 50 ml. The total
phenolic content and total flavonoid content of oil samples were
evaluated by methods described inprevious literature (Yang et al.,
2018). The antioxidant activity of each peanut oil sample was evaluated
using, the biochemical methods of DPPH and Ferric ion reducing
antioxidant power (FRAP) assays. The DPPH radical–clearing capacity was
measured following to previous research (Lin et al., 2019). Each oil
sample was diluted with acetone/methanol (2:8) to concentrations of 1
mg/mL, and then mixed together with DPPH radicals (0.2mM) of methanol
solution. After vigorously shake, the mixture was incubated at room
temperature for 30 min, and then measured absorbance at 517 nm. The FRAP
was measured following to the method used in previous research
(Fernández–Arroyo et al., 2011). Each oil sample was diluted with
acetone/methanol (2:8) to concentrations of 2 mg/mL, and then mixed with
FRAP reagent (acetate buffer, FeCl3 solution, and TPTZ;
10:1:1). After vigorously shake, the mixture incubated at room
temperature for 10 min, and next, measured absorbance at 595 nm. Trolox
was used as the positive control.