Sebastián Sánchez

Olive oils are globally valued for their nutritional properties and health benefits; however, pesticide residues represent an increasing concern for product safety and consumer trust. This study examined pesticide contamination in olive oils from three distinct sources: an experimental farm, olive groves adjacent to highways, and commercial oils available on the market. Gas and liquid chromatography coupled with mass spectrometry identified eleven active substances, oxyfluorfen, azoxystrobin, difenoconazole, diflufenican, phosmet, lambda-cyhalothrin, cyfluthrin, deltamethrin, cypermethrin, trifloxystrobin and tebuconazole. Most residues in olive oil samples were below European Union Maximum Residue Limits (MRLs), except azoxystrobin, detected at 0.02 mg/kg, exceeding the legal limit of 0.01 mg/kg. The persistence of oxyfluorfen despite no recent applications, suggests cross-contamination or soil accumulation from historical use in the experimental farm. Notably, phosmet, an organophosphate insecticide banned in the EU (Regulation 2022/94, Nov 2022), was detected in commercial virgin olive oils from both sampling campaigns (0.001 and 0.011 mg/kg), suggesting potential illegal use, environmental persistence, or blending with imported non-EU oils. No glyphosate residues were detected, consistent with its low octanol–water partition coefficient and high-water solubility, which limit its partitioning into lipid matrices. The presence of multiple pesticides in olive pomace oils with total concentrations up to 0.098 mg/kg, suggests deficiencies in the refining process. These findings highlight critical control points throughout the production chain, from cultivation practices to processing methods, with implications for monitoring strategies and food safety protocols to protect consumers.

Lipid recovery efficiency from microalgal biomass is a critical factor in the commercial viability of biodiesel. Scenedesmus sp. presents a robust cell wall that necessitates the evaluation of specialised disruption techniques to enhance intracellular lipid release and subsequent fuel quality. This study investigated the efficacy of five cell disruption methods—microwaves, ultrasonication, lyophilisation, autoclaving, and electroporation—integrated with three distinct extraction procedures: cold extraction, Soxhlet extraction system, and microwave-assisted extraction. The qualitative and quantitative impacts of these treatments were assessed by analysing the fatty acid methyl ester (FAME) profiles via gas chromatography (GC) following transesterification. The highest total lipid yield (88.97%) was achieved through a combination of microwave disruption and Soxhlet extraction. However, the maximal proportion of methyl esters was obtained when ultrasonication was paired with microwave-assisted extraction (97.64%). Surface analysis using scanning electron microscopy (SEM) of samples subjected to different disruption procedures could support the conclusions. Similarly, when the microalgal biomass was lyophilised beforehand, microwave extraction increased the oleic acid content. These results indicate that the choice of disruption and extraction protocols significantly influences both lipid recovery rate and the proportion of fatty acids in the chemical composition of microalgae. Tailoring these processes is essential for optimising the fatty acid profile for high-quality biodiesel production.

In this work, biochars were produced by pyrolysis of exhausted olive pomace and evaluated as low-cost adsorbents for the removal of methylene blue (MB) from aqueous solutions. The biochar obtained at 400 °C for 1 h, which exhibited the best adsorption performance, was characterized by FTIR, N₂ adsorption–desorption isotherms, SEM-EDX, and proximate analysis, revealing a mesoporous structure with a relatively low specific surface area but enriched in surface functional groups, likely due to the partial degradation of lignocellulosic components. Adsorption experiments were conducted to optimize operational parameters such as solid particle size (2–3 mm), agitation speed (75 rpm), and bioadsorbent dosage (1 g per 0.05 L of MB solution), which allowed for dye removal efficiencies close to 100%. Kinetic studies showed that MB adsorption followed a pseudo-second-order model, while equilibrium data at 30 °C were best described by the Langmuir isotherm (R² = 0.999; SE = 4.25%), suggesting monolayer coverage and strong adsorbate–adsorbent affinity. Desorption trials using water, ethanol, and their mixtures resulted in low MB recovery, whereas the addition of 10% acetic acid significantly improved desorption performance. Under optimal conditions, up to 52% of the retained dye was recovered.

The goal of this study was to determine the composition of olive oils from four North Moroccan provinces (Larache, Chefchaouen, Ouazzane and Tetouan), one of the main productive zones nationwide. For this purpose, we evaluate the quality parameters, phenolic compounds, oxidative stability, fatty acids, sterols, uvaol + erytrodiol, carotenoids and chlorophylls of three varieties (‘Picholine marocaine’, ‘Haouzia’ and ‘Menara’) in three campaigns (2019/2020 to 2021/2022) and in three harvesting periods. Another aim was to research the effect of natural microtalc (NMT) on the compounds of olive oils, and to evaluate whether the addition of microtalc to olive pastes during the malaxation stage influences in the quality of olive oils. From the results, it was observed that industrial yields increase when natural microtalcs were used during the oil production. Considering the quality parameters, the olive oils produced with NMT showed lower values when compared with those obtained without any addition. Also, oils produced with NMT showed a higher content in phenolic compounds as well as a greater oxidative stability. It is worth highlighting that the maximum content in phenolic compounds, adding NMT during the extraction process, was determined in oils obtained from the ‘Picholine marocaine’ variety from Chefchaouen, harvested in the 2019/2020 campaign, with 848.71 mg/kg oil, with a value of oxidative stability of 78.68 h.

This work aims to enhance the food safety of olive oils by detecting critical points where contamination can be generated by heavy metals and phthalic acid esters (PAEs). Samples of commercial oils were collected from the Spanish market during the 2021/2022 and 2022/2023 campaigns and stored in different packagings (glass, polyethylene terephthalate, tin can, porcelain, aluminum and cardboard). This was performed to establish the possible influence of the packaging material on the presence of contaminating compounds, concretely PAEs and heavy metals. Oils from different categories (extra virgin, virgin, olive oil, and olive pomace oil) were also acquired. Determination of PAEs contents revealed the presence of Di(2-ethylhexyl) phthalate (DEHP), Di-isobutyl phthalate and Di-isononyl phthalate. DEHP was detected in 6 out of 18 samples, with concentrations ranging from 0.1 to 0.23 mg/kg. Phthalates, particularly DEHP were most commonly found in PET, but also in glass, porcelain, and cardboard containers. In relation to heavy metals, copper was detected in all tested samples, exceeding the standard in samples of extra virgin in glass and porcelain containers, as well as in olive pomace oil (in PET), with concentrations varying from 0.04 to 0.18 mg/kg oil. Notably, antimony ions were absent in all the tested containers.

A sequential valorization process of sunflower stalks was carried out using nitric acid (0.1–2 mol dm⁻³) as a hydrolytic agent and fermenting the hydrolysate of higher sugar concentration in the presence of the non-conventional yeast Hansenula polymorpha. Values reached for ethanol yield (0.25 g g⁻¹) and xylitol yield (0.14 g g⁻¹) were higher than those achieved after pretreatment with other acids in previous studies. The effect of acid treatment with nitric, phosphoric, and sulfuric acids on the separated solid fractions was evaluated to determine its potential use as solid biofuel by FTIR and SEM determinations. A significant loss of lignin and hemicellulose was found in the solid treated with nitric acid, while a higher HHV was obtained when pretreated with phosphoric acid (19.16 MJ kg⁻¹) and sulfuric acid (19.12 MJ kg⁻¹). A subsequent enzymatic hydrolysis of acid-pretreated solids showed that the nitric acid pretreatment increased the availability of glucose from the cellulose fraction to a greater extent than the other two acids, by reducing the hemicellulose fraction to 0.7% and the lignin fraction to 2.5%. This study shows that pretreatment of biomass with nitric acid leads to better fermentation results to obtain biofuels such as ethanol, which could be further increased by additional enzymatic hydrolysis, while pretreatment with the other two acids generates better solid fuels.

Vibrational spectroscopic techniques have gained significant attention in recent years for their potential in the rapid and efficient analysis of virgin olive oils, offering a distinct advantage over traditional methods. These techniques are particularly valuable for detecting and quantifying bio-active compounds that contribute to the nutritional and health benefits of virgin olive oils. This comprehensive review explores the latest advancements in vibrational spectroscopic techniques applied to virgin olive oils, focusing on the detection and measurement of key bio-active compounds such as unsaturated fatty acids, phenolic compounds, and other antioxidant compounds. The review highlights the improvements in vibrational spectroscopy, data processing, and chemometric techniques that have significantly enhanced the ability to accurately identify these compounds compared to conventional analytical methods. Additionally, it addresses current challenges, including the need for standardized methodologies and the potential for integrating vibrational spectroscopy with other analytical techniques to improve accuracy and reliability. Finally, findings over the last two decades, in which vibrational spectroscopy techniques were effectively used for the detailed characterization of bio-active compounds in virgin olive oils, are discussed.

The olive oil industry, one of the largest industries in the Mediterranean basin and in other countries around the world, is fundamentally composed of olive groves, olive oil mills, pomace oil extraction plants, and oil refineries