Browsing by Author "Landoulsi, Fedi"
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- Impact of rancidity on the olive oil quality, antioxidant activity, and sensory profilePublication . Landoulsi, Fedi; Rodrigues, Nuno; Pereira, J.A.; Khemakhem, MaissaOlive oil is one of the most appreciated fats, especially in the Mediterranean region. However, as it is an oil, it deteriorates relatively quickly, resulting in the development of rancidity. In view of this, the present study aims to evaluate the minimum sensitivity in detecting this defect. To this end, different batches of extra virgin olive oil with medium and intense green fruitiness were prepared, to which different percentages of extremely rancid olive oil were added in order to determine the detection limit of rancidity. Quality parameters were evaluated such as free acidity, peroxide value, and specific extinction coefficients (K232, K268) to measure oxidation levels. Additionally, antioxidant activity and total phenolic content were examined. Sensory properties were also evaluated through trained tasting panels and the use of E-nose technology for more advanced detection of adulteration. The results demonstrated that even small amounts (from 4%) of rancid olive oil significantly deteriorated the quality of both medium and intense fruitiness olive oils. Free acidity increased significantly however, all samples except the one containing 100% rancid oil remained within the classification of extra virgin olive oil (EVOO). Regarding peroxide values, a significant decrease was observed in both types of olive oil, though the values remained below the legal limit. For the specific extinction coefficients K232 and K268, significant increases were recorded in both oil types. Rancidity was detectable from 16% adulteration in the medium fruitiness oil and from 32% in the intense fruitiness oil for K232, and from 16% in both oil types for K268. Sensory analysis revealed a decline in desirable attributes such as green fruitiness, apple, tomato, and fresh herbs, alongside an increase in the negative attribute of rancid flavor, which became perceptible from as low as 4% rancid oil addition in both types. For the antioxidant activity, a significant decrease was observed in DPPH value and total phenols content with the addition of rancid olive oil, especially in the case of intense fruitiness. The E-nose analysis also confirmed the presence of rancidity and enabled the classification of olive oils into categories such as extra virgin olive oil (EVOO) (for 0% and 2% added rancid olive oil), VOO (for 4% and 8% added rancid olive oil), and lampante olive oil (LOO) for other percentages such as 16% and 32%, thus providing an effective non-invasive tool for detecting adulteration. These results from the E-nose are almost similar to those from the tasting panel. This research highlights the urgent need for reliable analytical methods to ensure olive oil authenticity and protect consumer trust in a market increasingly threatened by fraudulent practices.