Development of a fingerprinting approach to determine the geographical origin of vegetable oils: A case study for rapeseed oil from Hesse (Germany)

Vegetable oils play crucial roles as both a food source and a renewable energy resource. Determining their geographical origin is essential for ensuring food safety, health, and energy sustainability. While stable isotopic analysis of light elements combined with chemometric techniques has been effective in tracing the geographical origin of vegetable oils, the potential of stable hydrogen isotopic composition (δ2H) of fatty acids (FAs) as analytical markers and the associated fingerprinting approach remains underexplored, particularly for rapeseed oil, which is the third-largest vegetable oil globally. This dissertation aimed to develop a fingerprinting approach for determining the geographical origin of vegetable oils, using rapeseed oil as a case study. The research objectives are threefold: (1) to optimize the sample preparation method for efficient and high-throughput measurement of δ2H of FAs in rapeseed; (2) to analyze the spatial distribution of δ2H of FAs in rapeseeds from different regions and assess its correlation with climatic and soil factors; (3) to establish classification models using δ2H of FAs and elemental composition of rapeseed to differentiate geographical origins, including distinguishing between Hesse and other regions, as well as various regions within Hesse. A rapid and straightforward sample preparation method by Garcés & Mancha (1993) enables the direct conversion of rapeseed into fatty acid methyl esters (FAMEs). The addition of 2,2-dimethoxypropane (DMP) for effective conversion was evaluated through control experiments to assess its impact on the isotopic composition of individual FAMEs using gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-Py-IRMS). For the second and third objectives, a total of 121 rapeseed and soil samples were collected from Hesse, Germany, during 2017-2020, and 28 rapeseed samples from Jianhu County, Jiangsu Province, China, in 2019. The δ2H of major FAs (C18:1, C18:2, C18:3, C16:0) in rapeseed were determined by GC-Py-IRMS, while the ...