L’economic importance of olive oil is evident in trade data, with production tripling over the last 60 years. In fact, it reached a peak of 3,379,000 tonnes in 2017-2018. According to foreign trade statistics of 102 countries, global imports of “Olive oil and its fractions, including refined, but not chemically modified” exceeded $9.74 billion in 2022. However, despite its recognized value health and economic, the problem of adulteration with cheaper vegetable oils or lower quality olive oils remains a significant and ongoing challenge.
The complexity of olive oils, influenced by various factors, represents a challenge in establishing consistent parameters and methods for authentication and traceability. Several procedures have been developed to detect olive oil adulteration, which can be classified into chemical methods, biological methods, sensory methods and other approaches such as designing sensors with suitable sensitivity and overcoupled resonant modes of fiber gratings at long period. However, international regulatory bodies such as the European Union and the International Olive Council have approved several approaches to detect and quantify various compounds in olive oil. Advanced analytical and detection methods, including mass spectrometry (MS), NMR spectroscopy, optical and chromatography methods based on differential scanning calorimetry (DSC) can be employed to detect olive oil adulteration.
Some adulterants present in olive oils can pose health risks to consumers and damage their economic interests. To safeguard public health and economic well-being, it is crucial to develop efficient and accurate analytical approaches to monitor and detect olive oil adulteration.
There is a growing trend towards using chemometric methods and multivariate statistical models to detect olive oil adulteration. Chemometrics and pattern recognition methods play a critical role in olive oil authentication by enabling the classification, discrimination and measurement of different varieties, origins and potential adulterants. These techniques use statistical and mathematical tools to analyze complex data sets generated by spectroscopy and chromatography, among other analytical measurements. By building models based on characteristic parameters and patterns, these methods can effectively distinguish between authentic olive oil and adulterated or lower-quality oils.
Adulteration of extra virgin olive oil: new techniques to detect fraud
Recent studies have successfully improved the detection limit by combining different methods or modifying existing ones. Each technique has its strengths and limitations, making it more suitable for specific types of adulteration.
NMR reveals the chemical composition and structure of oils, while chromatography separates and identifies individual components. DNA-based methods detect genetic material, and the electronic nose detects differences in smell or taste. In practice, a combination of multiple analytical techniques improves the accuracy and reliability of olive oil adulteration detection.
Chemometrics, a mathematical and statistical approach to analyzing large data sets, helps interpret results and identify patterns and trends that may indicate adulteration.
Optical methods have significant advantages in detecting olive oil adulteration, including high sensitivity, nondestructiveness, and rapid analysis. However, researchers and practitioners should consider potential interferences and the resources needed to implement these methods effectively. Chromatography-based methods offer excellent separation capabilities, high selectivity and quantitative analysis. This quantitative analysis is essential to assess the severity of adulteration and ensure compliance with regulatory standards. However, when implementing these methods it is necessary to consider the need for specialized equipment and expertise, complex sample preparation and limitations in the detection of some adulterants. NMR is an advanced detection method with very high sensitivity and can be applied when a solid decision and also confirmation of other methods is needed. Furthermore, NMR requires specialized and expensive instrumentation with a person experienced in processing NMR spectra.
Olive oil authentication has become increasingly important in recent years, leading to the development of various detection strategies to distinguish pure, high-quality olive oil from lower-quality oils or illegal additives, as well as to differentiate olive oils from different regions. Optical and chromatography-based methods, combined with MS, DNA, NMR and other techniques such as dielectric spectroscopy, DSC, TGA and EN, together with chemometric analysis, are favorable for olive oil authentication. However, specific spectroscopic methods for the classification of virgin olive oil are rare and infrared spectroscopy has its limitations. However, when combined with chemometric analysis, infrared spectroscopy has shown the potential to classify or differentiate olive oils based on their quality, particularly for binary models distinguishing defective/non-defective samples or olive oils edible/non-edible.
DNA analysis has also proven to be an effective method for detecting adulterants in extra virgin olive oils. DNA analyzes have a remarkable capacity for discrimination since the unique identity of a species or range is determined primarily genetically. Molecular markers such as single nucleotide polymorphisms (SNPs), simple sequence repeats (SSRs), sequence characterized amplified region (SCAR), and amplified fragment length polymorphism (AFLP) play a crucial role in assessing validity of olive oil providing insights into genetic variations. These markers, consisting of di-, tri-, tetra- and penta-nucleotide sequences, as well as SNPs, have been successfully employed to differentiate the varietal origin of olive oils. The use of SSRs represents a powerful and cost-effective method for genetic traceability. The multi-species DNA sensor can detect a minimum amount of adulterant of less than 5–10% in blended oils. DNA-based methods can be used with particularly good reproducibility and specificity to authenticate the varietal composition of olive oil blends, detect adulterations with oils of different plant origins, and ensure the traceability and authenticity of olive oil products. ‘olive.
