Detection of Corn Oil in Adulterated Sesame Oil by Chromatography and Carbon Isotope Analysis

This study was performed to the development of methods for the identification and detection of corn oil in adulterated sesame oil. The fatty acids composition and carbon isotope ratio of authentic sesame oil and adulterated sesame oil with corn oil were studied by using GC-FID and IRMS. The content of palmitic (P), linoleic (L), and linolenic (Ln) acids increased gradually as the mixed rate of corn oil was increased, whereas the content of stearic (S) and oleic (O) acids decreased. On increasing the mixing ratio of corn oil, the stearic acid contents and the (L × L)/O ratio showed significant differences between authentic and adulterated sesame oils (p < 0.05). The δ¹³C‰ value for authentic sesame oil and corn oil fell into the range of −27.68 to −29.26‰ and −16.51 to −17.27‰. The adulterant had more carbon-13 compared with those of authentic sesame oil and the δ¹³C‰ value was increased linearly (r ² = 0.996). Therefore, the combination of the stearic acid% (56.1) and the carbon isotope ratio (> −27.0‰) turned out to be a good tool for detecting the adulteration of sesame oil with the cheaper corn oil, up to the 10% level.