Materials
SBO (Crisco®, refined), olive
(Bertolli®, cooking oil), canola oil
(Crisco®), avocado oil (Spectrum
Culinary®, refined), and corn oil
(Mazola®) were purchased from a grocery store in
Peoria, IL, USA. High oleic soybean oil
(HO SBO,
Plenish®) was provided by DuPont (Johnston, IA, USA).
Aluminum oxide, amino acids, food grade mixed tocopherols, and
monosodium L-glutamate were obtained from Sigma-Aldrich (St. Louis,
Missouri, USA). According to the certificate of analysis from the
manufacture, the mixed tocopherols contains 13.2% α-, 0.16% β-, 42.9%
γ-, and 16.3% δ-tocopherols in weight (74.0% total).
Considering the purity (74.0%),
the factor 1.35 was used to obtain an accurate concentration of mixed
tocopherols in oil. L-Proline sodium salt was purchased from
Combi-Blocks (San Diego, CA, USA). TBHQ, sodium hydroxide (NaOH), and
potassium hydroxide (KOH) were purchased from Fluka (Deisenhofen,
Germany). Tetrahydrofuran (THF), dichloromethane, ethanol, and hexane
were obtained from Fisher Scientific (Fair Lawn, NJ, USA).