Assessment and quantification of extra virgin olive oil adulteration
TRICLOPS spectrometer offers a powerful, non-destructive method for detecting and quantifying olive oil adulteration.
TRICLOPS spectrometer is suitable for the characterization of liquid samples by their absorbance spectra.
We analyzed the capacity of the spectrometer in recognizing pure extra virgin olive oil (EVOO), detecting and quantifying adulterations with sunflower oil.
Here we show the absorbance spectra of EVOO at different levels of adulteration.
Distinctive absorption features are noticeable, especially in the MIR region ~ 2.5 – 3 μm, characterizing the presence and the concentrations of extra virgin olive oil and adulterants.
These measurements were used to train a regression model.
The accuracy of this regression model implies that TRICLOPS is able to rapidly identify adulterated EVOO samples, and quantify their purity.
Introduction
Adulteration of EVOO, a high value product known for its culinary quality, is a significant concern in the food industry. It can occur at various stages of production and distribution, making it challenging to detect using traditional methods.
Mixing EVOO with lower-cost oils such as sunflower oil not only deceives consumers but also compromises the nutritional and sensory properties of the product. For these reasons ensuring the authenticity of EVOO is crucial for protecting both consumers and reputable producers.
TRICLOPS ultrabroadband spectrometer offers a powerful, non-destructive method for detecting and quantifying such adulteration.
Measurements
An experimental analysis was conducted mixing EVOO with different amounts of sunflower oil. We tested 23 level of adulteration, from 0% (pure EVOO) to 100% (pure sunflower oil). The measurements were done in transmission mode, using a cuvette of 1 mm thickness and a halogen light for illumination.
Figure 1
Experimental results
The spectra were obtained using TRICLOPS in full detection range (400–4500 nm) with fine (10 cm-1) resolution averaging 20 scans (10 seconds total collection time), the corresponding intensity spectra for the different fat contents are shown in Figure 2 a).
The light from the illuminating halogen lamp in absence of the sample was used to calculate the absorbance spectra. Furthermore, a pre-processing pipeline (wavelength set reduction → normalization → baseline correction) was applied to reduce the variability caused by external parameters (e.g. different alignment, presence of air bubbles in the cuvette etc.).
The resulting pre-processed spectra, in Figure 2 b), show distinctive absorption peaks of the extra virgin olive oil and the adulterant sunflower oil in the NIR and MIR spectral regions. These peaks allow us to distinguish the two liquids and allow to determine their relative concentrations.
Figure 2: a) Raw spectra from TRICLOPS b) Pre-processed spectra
Data analysis
A predictive model was calibrated using a Partial Least Squares algorithm, validated by leave-one-out cross validation. An additional analysis on the contribution of the single wavelengths was performed to reduce the predictors set, maximizing the model performances.
The considered figures of merit are the root mean squared error of calibration and cross validation (RMSEC, RMSECV), the mean average error of cross validation (MAECV) and the coefficient of determination (R^2). The results are shown in the table and figures 3 and 4.
Figure 3 (on the left): Fitted vs Labeled EVOO content
Figure 4 (on the right): Predicted vs Labeled EVOO content
Conclusion
In this application note the effectiveness of TRICLOPS for the detection and quantification of EVOO adulteration with sunflower oil was demonstrated, ensuring a mean average error in the CV predicted values of 1.79% in the adulterant content.
TRICLOPS guarantees a fast, reliable, and non-disruptive instrument with a unique spectral range useful for assessing quality in olive oil industry and more generally in whole food industry.
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