Reliable Classification of Olive Oil Origin Based on Minor Component Profile Using ¹H‐NMR and Multivariate Analysis

Abstract

Mislabeling of olive oil with respect to its geographical origin is a frequently encountered fraud. Although according to European Regulation (EU) No 29/2012 it is mandatory to declare the geographical origin of an olive oil on the label, no generally accepted analytical method exists to verify this labeling. As Italy, Greece, and Spain are the main producing countries in the Mediterranean Area, the aim is to develop an analytical method that allows classification of these three origins and which can be reliably applied to routine samples. A protocol for the extraction and subsequent 1H‐NMR measurement of the polar fraction of olive oil is developed and applied to a large number of authentic reference samples. A classification model is developed which obtains 96% of correct classification during cross‐validation. The method is being routinely applied for testing commercial off‐the‐shelf olive oils, and its accuracy is continuously verified. Practical Applications: In addition to checking the geographical origin of an olive oil, the developed protocol allows to analyze the polar constituents of an olive oil in great detail with little effort, which should prove useful also for other applications, for example, quantitation of phenols or detection of admixtures with other vegetable oils.

Characterization of Phenolic Compounds Extracted from Cold Pressed Cactus (Opuntia ficus-indica L.) Seed Oil and the Effect of Roasting on Their Composition

“…Especially, expensive oils like cactus seed oil are suspicious to be subjected to different kinds of food fraud. Different types of vegetable oils have very characteristic fingerprints of phenolic compound patterns that can be used to differentiate different oils, mixtures of oils, but also identify the origin of oils [ 30 , 31 ]. Therefore, it is necessary to know more about the composition of phenolic compounds in cactus seed oil.…”

Development of Chemometric Models Based on a LC-qToF-MS Approach to Verify the Geographic Origin of Virgin Olive Oil

“…As a consequence, the National Reference Centre for Authentic Food (NRZ-Authent) in Germany was established in 2017 [ 2 , 3 ]. Moreover, the search for reliable and robust methods for the detection of food fraud is an ongoing story and many research groups dedicate a lot of time to this topic [ 5 , 6 , 7 , 8 , 9 ].…”

“…Recently, several papers on the differentiation of olive oil from different regions using different analytical methods combined with multivariate techniques have been published. Such methods are MS-based techniques [ 16 , 17 ], HPLC [ 18 ], genomics [ 19 ], stable isotope ratio analysis [ 5 , 20 ], NMR [ 9 , 21 , 22 ], NIR [ 7 ] or two-dimensional GC-MS [ 23 ]. Regarding the application of NMR in questions of origin verification there are only few studies available, mostly based on 1H-NMR as the generation of quantitative data is faster and simpler in comparison to 13C-NMR [ 21 ].…”

“…In a recent study an alternative sample preparation was suggested, which allows to focus on the minor components like phenols, aldehydes and ketones without multiple pulse sequencing [ 9 ]. The presented model based on the developed extraction protocol allowed to differentiate olive oils from Italy, Greece and Spain with a correct classification of 96% during cross-validation [ 9 ]. Another analytical technique used for origin determination of olive oils is NIR [ 7 , 24 ].…”

“…This often allows the discrimination of olive oils from different regions whereas the separation of oils from different countries is difficult since the huge variation leads to overlapping between samples from several countries. In a preliminary study with data on the fatty acid profile Winkelmann and Küchler showed a satisfactory differentiation between oils from two distinct regions, but much more overlapping when data from all regions in two countries were considered [ 9 ].…”