Percorrer por autor "Alimi, Siwar"
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- Influence of household conditions on the shelf-life and polyphenolic-related health claim of Cobrançosa extra virgin olive oilPublication . Alimi, Siwar; Rodrigues, Nuno; Veloso, Ana C. A.; Cruz, Rebeca; Khemakhem, Maissa; Pereira, José Alberto; Casal, Susana; Peres, António M.This study examines how typical household conditions after bottle opening affect the physicochemical, sensory, and bioactive properties of cv. Cobrançosa extra virgin olive oil (EVOO), attempting to define kinetic models to predict the shelf-life (SL) during domestic use. For 9 weeks, EVOO amber glass bottles (750 mL), exposed to light (n = 5) or darkness (n = 5), at 18 ± 2 ºC, were opened/shaken daily to simulate household use, with oil removed weekly. In light-exposed samples, the peroxide value (PV) imposed EVOO declassification at week five, with intense rancidity at week eight (≥ 3.5), rendering the oil unsuitable for consumption. On the contrary, light-protected oils had only a downgrade to virgin olive oil due to a K232 rise. Acidity was preserved, as was the health claim supported by tyrosol/hydroxytyrosol polyphenols. Kinetic models (zero-, first-, and second-order) supported on the oxidation indicators (PV, K232, or K268), allowed determining reaction rates by linear regression (correlation coefficients: 0.942 to 0.997). For light-exposed oils, PV was the most reliable indicator of SL, predicting from a second-order TRUL model a preservation of the EVOO grade for 35 ± 2 days, in agreement with the experimental SL (28–35 days). For light-protected oils, K232 was the most accurate SL indicator, predicting a SL of 49 ± 4 days using a zero-order TRUL model, consistent with the experimental SL (49–56 days). The models were validated using SL literature data from cvs. Arbequina, Istarska Bjelica, and Buža olive oils, confirming their applicability to various cultivars and highlighting oxidation’s role, particularly photo-oxidation, in EVOO degradation during domestic use.
- Quality grade evolution and health claim fulfillment of olive oils under simulated domestic consumption: kinetic modelling and shelf life predictionsPublication . Alimi, Siwar; Peres, António M.; Casal, Susana; Khemakhem, MaissaOlive oil has always played a vital role in the Mediterranean diet, well renowned for its nutritional properties and related health benefits. This is largely attributed to its high concentration of monounsaturated fatty acids and bioactive minor compounds, such as polyphenols. This study aimed to assess how typical household consumption conditions influence the physicochemical and sensory properties of extra virgin olive oil (EVOO), as well as its compliance with the European Union (EU) health claim. The results of the analysis of ten bottles stored in darkness and exposed to light under simulated household conditions, demonstrated an increase in PV and extinction coefficients over the 9-week period, with a more pronounced rise in the light-exposed samples. In these samples, PV increased by 81.2%, and at 6 weeks it exceeded the legal EU thresholds for EVOO/VOO classification. In contrast, oils stored in darkness kept all physicochemical parameters within legal limits allowing EVOO or VOO classification, up to or beyond the seventh week, respectively. Also, by the eighth week, sensory analysis revealed the presence of rancid in light-exposed samples, with intensities ranging from 3.6 to 6.1, indicating advanced oxidation and rendering the oil unsuitable for consumption (lampante oil). Kinetic models were developed to predict the shelf life (SL) of commercial grade EVOO under household conditions, applying zero-, first-, and second-order kinetic models for PV, K232, and K268 in both dark and light storage conditions. The models fitted well the experimental data (R-Pearson values ranging from 0.89 to 0.97), with PV emerging as the most sensitive SL indicator under these conditions. The estimated SL was approximately 15 days for light-exposed oils and 63 days for oils stored in darkness. The greatest variation in SL predictions, based on PV, K232, or K268, was observed in the light- exposed samples. Photo-oxidation led to a rapid increase in PV, in contrast to the slower rise in extinction coefficients, which are associated with secondary oxidation products that form when oxygen availability diminishes. Regarding the health claim, the content of hydroxytyrosol and tyrosol derivatives remained relatively stable throughout the 9-week period in both dark- and light-stored oils, ranging from 12 to 13 mg/20 g of oil, significantly exceeding the minimum required by the EU regulation. In conclusion, typical household conditions significantly impact the quality of olive oil. Storing olive oil in darkness can extend its SL by 3 to 4 times, compared to light-exposed conditions, in terms of maintaining its EVOO classification.