New Spectroscopy Method Shows Promise for Detecting Olive Oil Fraud

With extra virgin olive oil prices at record highs, fraud prevention in the olive oil industry has become critical. Recognizing this, researchers from the University of Cordoba, María-del-Mar Garrido-Cuevas, Ana-María Garrido-Varo, Paolo Oliveri, María-Teresa Sánchez, and Dolores Pérez-Marín, conducted an in-depth study to validate visible and near-infrared spectroscopy (vis -NIR or vis-NIRS) as a screening method to distinguish between high-grade extra virgin olive oil (EVOO) and virgin olive oil (VOO). Published in the journal Food Research International, their research highlights the potential of vis + NIR for quick and affordable categorization, bolstering quality control in olive oil distribution (1).

The Challenge in Olive Oil Authentication

Traditional olive oil grading methods rely on the panel test, where trained tasters evaluate sensory characteristics to classify oils. However, this process is costly, time-consuming, and subjective. According to the researchers, panel tests are limited by daily sample capacity and have significant variability among tasting panels, especially with borderline samples like EVOO and VOO. This poses a challenge for regulators who aim to prevent fraud and protect consumers. Consequently, the olive oil industry is seeking instrumental methods to supplement panel tests and reduce reliance on human assessors (1–2).

Spectroscopy as a Solution

The research team at Cordoba’s Faculty of Agriculture and Forestry Engineering explored vis-NIR as a potential non-targeted method (NTM) to aid in olive oil authentication. Unlike conventional methods, which often focus on detecting specific chemical markers, NTMs like vis-NIR analyze a broader "fingerprint" of the sample, making them effective for distinguishing categories without requiring predetermined indicators. This study is part of an increasing trend in food quality research where spectroscopy, particularly NIR, is leveraged for its speed, affordability, and non-destructive measurement capabilities (1).

Methodology and Findings

In their study, the team analyzed 161 olive oil samples using a vis-NIR monochromator. They employed a partial least squares (PLS) density model to initially classify samples, and further discriminant models, including PLS-discriminant analysis (PLS-DA), were tested to optimize categorization accuracy (1).

The results were promising: after extensive data pre-treatment and model refinement, the researchers achieved a correct classification rate (CCR) of 82.35% for EVOO and 66.67% for VOO in external validations. These rates demonstrate the potential of vis-NIR as a reliable first-level screening tool that can identify suspect samples for further analysis using official methods (1).

Implications for the Industry

The findings present significant implications for olive oil regulation and commerce. The ability to use vis-NIR as an NTM means that large volumes of oil could be screened rapidly and cost-effectively, ensuring more extensive monitoring of olive oil quality. According to the authors, such technology could support the traditional panel test, providing initial screenings that reduce the panel’s workload and increase efficiency. The study’s results, however, are preliminary, and further validation, including international protocols and inter-laboratory tests, will be required before widespread adoption (1–2).

Future Directions

The researchers acknowledge that their work represents only a part of the larger goal of incorporating vis-NIR in regular olive oil testing. Ongoing research, funded by national projects, aims to validate these methods for broader application and test portable vis-NIR devices for in-situ testing. In the meantime, the team hopes that their findings will encourage international organizations like the International Olive Council (IOC) to consider NIR-based methods in the ongoing development of fraud detection protocols (1–2).

In the view of María-del-Mar Garrido-Cuevas and her colleagues, vis-NIR could become a standard in fraud detection if further studies confirm its effectiveness. The team sees great potential for vis-NIR to be incorporated as a first-line screening tool in compliance with IOC regulations, giving producers, distributors, and regulators alike an additional layer of assurance for olive oil quality and authenticity (1).

References

(1) Garrido-Varo, A. M.; Oliveri, P.; Sánchez, M. T.; Pérez-Marín, D. In-House Validation of a Visible and Near Infrared Spectroscopy Non-Targeted Method to Support Panel Test of Virgin Olive Oils. Food Res Int. 2024, 192, 114799. DOI: 10.1016/j.foodres.2024.114799

(2) Hashempour-baltork, F.; Zade, S. V.; Mazaheri, Y.; Alizadeh, A. M.; Rastegar, H.; Abdian, Z.; Torbati, M.; Damirchi, S. A. Recent Methods in Detection of Olive Oil Adulteration: State-of-the-Art. J. Agric. Food Res. 2024, 16, 101123. DOI: 10.1016/j.jafr.2024.101123