Authentication of vegetable oils using isotope mass spectrometry

Abstract

Vegetable oils play an important role in the human diet. Both the physiological value of the product and its cost largely depend on the type of processed raw materials. In this regard, the establishment of the type of vegetable raw materials used for the production of vegetable oils is an important area of research in the identification of this product type. To date, one of the most informative methods for assessing the authenticity of plant raw materials is the method of isotope mass spectrometry. Thirty samples of vegetable oils produced from various raw materials and places of origin (Italy, Greece, Spain, Turkey, Armenia, Russia, Slovenia) were studied. The isotopic ratios of carbon, oxygen and hydrogen were measured in the samples. It is shown that the samples of corn oil (C4 type of photosynthesis) are characterized by the highest values of the indicator δ13C, from –17.00‰ to –17.73‰. The rest of the studied samples of vegetable oils were produced from C3 plants (grape seed oil, olive, linseed, sesame, pumpkin, mustard, sunflower, etc.). For them, the values of δ13C lie in the range from –26.60‰ to –31.14‰. Thus, the method of isotope mass spectrometry makes it possible to detect the introduction of corn oil into a product produced from plants with C3 type of photosynthesis, even in small quantities. In addition, this method enables establishing the introduction of cheap oils into corn oil. The values of the indicators δ18O and δ2H largely depend on the year of harvest and the climatic characteristics of the region where the raw materials grow. Thus, the values of the isotopic characteristics of the δ18O structural components of the oil samples from grape seeds produced in Turkey, Armenia and Italy have significant differences (19.40± 0.77‰, 16.55± 0.66‰ and 23.29± 0.93‰, respectively). The values of the isotopic characteristics of hydrogen δ2H of the sample from Armenia differed from the values of the samples from Turkey and Italy in the direction of a higher content of “light” isotopes (–189.86± 1.13‰, —163.17 ± 0.97‰ and –160.72± 0.97‰, respectively). The annual monitoring of these values, the creation of a database, as well as the use of statistical analysis methods will allow in the future identifying vegetable oils by their geographical origin with a high degree of reliability.

Keywords

• vegetable oils
• isotope mass spectrometry
• carbon isotopes
• oxygen
• hydrogen
• identification
• place of origin
• falsification