Determination of Edible Vegetable Oil Adulterants in Sesame Oil Using ¹H Nuclear Magnetic Resonance Spectroscopy

Abstract

An NMR method is reported for the determination of sesamin to verify the authenticity of sesame oil. The intensity of the well-resolved H2′ sesamin signal resonating at approximately 5.95 ppm is strongly correlated with the amounts of other types of vegetable oils present in the adulterated sesame oil using the relationship, y = 4.020x + 1.516 (r ²  = 0.9967). The H2′ peak intensity of sesamin was measured for sesame oil extracted directly from the mill-sourced sesame seeds because the sesame oils purchased from local markets could be adulterated. Additionally, the oils used were obtained from the seeds native to China and the Republic of Korea, because the sesamin concentrations may vary from region to region. The proposed ¹H NMR method allows for the simple identification and determination of cheaper vegetable oils used as adulterants in sesame oil. High-performance liquid chromatography was used to confirm the validity of the results obtained by NMR.

Keywords:

• ¹H NMR
• Authenticity of sesame oil
• Edible vegetable oil
• Sesame oil
• Sesamin

Notes

^a Unadulterated genuine sesame oil extracted directly from mill-sourced Korean sesame seeds.

^b Unadulterated genuine sesame oil extracted directly from mill-sourced Chinese sesame seeds. The amounts of sesamin in Chinese products were measured relatively with respect to that contained in Chinese sesame seeds.

^c The average sesamin H2′ NMR peak intensity in six genuine sesame oil samples produced in Korea was set to 1.

^d The sesamin content in six genuine sesame oil samples was measured using HPLC(5.96 ± 0.34 mg/g), and the average was set to 1.

^e The average sesamin H2′ NMR peak intensity in five genuine sesame oil samples produced in China was set to 1.

^f The sesamin content in five genuine sesame oil samples produced in China were measured using HPLC(5.61 ± 0.38 mg/g), and the average was set to 1.