Effects of Roasting Conditions on the Changes of Stable Carbon Isotope Ratios (δ13C) in Sesame Oil and Usefulness of δ13C to Differentiate Blended Sesame Oil from Corn Oil

Differentiating blended sesame oils from authentic sesame oil (SO) is a critical step in protecting consumer rights. Stable carbon isotope ratios (delta C-13), color, fluorescence intensity, and fatty acid profiles were analyzed in SO prepared from sesame seeds with different roasting conditions and in corn oil blended with SO. Sesame seeds were roasted at 175, 200, 225, or 250 degrees C for 15 or 30 min at each temperature. SO was mixed with corn oil at varying ratios. Roasting conditions ranging from 175 to 250 degrees C at the 30 min time point did not result in significant changes in delta C-13 (P > 0.05). Values of delta C-13 in corn oil and SO from sesame seeds roasted at 250 degrees C for 15 min were -17.55 and -32.13 parts per thousand, respectively. Fatty acid ratios, including (O + L)/(P x Ln) and (L x L)/O, where O, L, P, and Ln were oleic, linoleic, palmitic, and linolenic acids, respectively, showed good discriminating abilities among the SO blended with corn oil. Therefore, using different combinations of stable carbon isotope ratios and some fatty acid ratios can allow successful differentiation of authentic SO from SO blended with corn oil.