Chemical composition and sensory profiling of coffees treated with asparaginase to decrease acrylamide formation during roasting.

Acrylamide is an amide formed in the Maillard reaction, with asparagine as the primary amino acid precursor. The intake of large amounts of acrylamide has induced genotoxic and carcinogenic effects in hormone-sensitive tissues of animals. The enzime asparaginase is one of the most effective methods for lowering the formation of acrylamide in foods such as potatoes. However, the reported sensory outcomes for coffee have been unsatisfactory so far. This study aimed to produce coffees with reduced levels of acrylamide by treating them with asparaginase while retaining their original sensory and bioactive profiles. Three raw samples of Coffea arabica, including two specialty coffees, and one of Coffea canephora were treated with 1000, 2000, and 3000 ASNU of the enzyme. Asparagine and bioactive compounds (chlorogenic acids-CGA, caffeine, and trigonelline) were quantified in raw and roasted beans by HPLC and LC-MS, while the determination of acrylamide and volatile organic compounds was performed in roasted beans by CG-MS. Soluble solids, titratable acidity, and pH were also determined. Professional cupping by Q-graders and consumer sensory tests were also conducted. Results were analyzed by ANOVA-Fisher, MFA, PCA and Cluster analyses, with significance levels set at p ≤ 0.05. Steam treatment alone decreased acrylamide content by 18.4%, on average, and 6.1% in medium roasted arabica and canefora coffees. Average reductions of 32.5-56.0% in acrylamide formation were observed in medium roasted arabica beans when 1000-3000 ASNU were applied. In the canefora sample, 59.4-60.7% reductions were observed. However, steam treatment primarily caused 17.1-26.7% reduction of total CGA and lactones in medium roasted arabica samples and 13.9-22.0% in canefora sample, while changes in trigonelline, caffeine, and other evaluated chemical parameters, including the volatile profiles were minimal. Increasing enzyme loads slightly elevated acidity. The only sensory changes observed by Q-graders and or consumers in treated samples were a modest increase in acidity when 3000 ASNU was used in the sample with lower acidity, loss of mild off-notes in control samples, and increased perception of sensory descriptors. The former was selected given the similarity in chemical outcomes among beans treated with 2000 and 3000 ASNU loads.

Evaluating the human neurotoxicity and toxicological interactions impact of co-occurring regulated and emerging mycotoxins.

Mycotoxins can inflict harmful effects on diverse organs, and mounting evidence indicates their potential involvement in human neurodegenerative diseases. Given the common occurrence of these toxins in food, there is an increasing demand for a comprehensive assessment of their combined toxicity to enhance our understanding of their potential hazards. This research investigates mycotoxin exposure from widely consumed cereal-based products, including enniatin B (ENNB), sterigmatocystin (STG), aflatoxin B1 (AFB1), cyclopiazonic acid (CPZ), citrinin (CIT), and ochratoxin A (OTA). Employing the median-effect equation based on Chou and Talalay's mass-action law, we assessed their cytotoxicity in human SH-SY5Y neuronal cells. Notably, ENNB displayed the highest neurotoxicity (IC50 = 3.72 µM), followed by OTA (9.10 µM) and STG (9.99 µM). The combination of OTA + STG exhibited the highest toxicity (IC50 = 3.77 µM), while CPZ + CIT showed the least detrimental effect. Approximately 70 % of tested binary combinations displayed synergistic or additive effects, except for ENNB + STG, ENNB + AFB1, and CPZ + CIT, which showed antagonistic interactions. Intriguingly, the senary combination displayed moderate antagonism at the lowest exposure and moderate synergism at higher doses. OTA exhibited predominantly synergistic interactions, comprising approximately 90 %, a noteworthy finding considering its prevalence in food. Conversely, ENNB interactions tended to be antagonistic. The most remarkable synergy occurred in the STG and CIT combination, enabling a 50-fold reduction in CIT dosage for an equivalent toxic effect. These findings highlight the biological relevance of robust synergistic interactions, emphasizing the need to assess human exposure hazards accurately, particularly considering frequent mycotoxin co-occurrence in environmental and food settings.

Investigating the individual and mixture cytotoxicity of co-occurring aflatoxin B1, enniatin B, and sterigmatocystin on gastric, intestinal, hepatic, and renal cellular models.

This study investigates the individual and combined effects of the mycotoxins, Aflatoxin B1 (AFB1), Enniatin B (ENNB) and Sterigmatocystin (STG), on the cellular viability of gastric (NCI-N87), intestinal (Caco-2), hepatic (Hep-G2) and renal (Hek-293) cells, shedding light on synergistic or antagonistic effects using a constant ratio combination design proposed by Chou-Talalay. These toxins are prevalent in cereal-based foods, frequently consumed by children which raises concerns about their exposure to these mycotoxins. This population is particularly vulnerable to the effects of these toxins due to their underdeveloped organs and incompletely structured physiological processes. Results showed that ENB was the most toxic of the three mycotoxins across all cell lines, while STG and AFB1 showed lower toxicity. The combination of ENNB + STG was found to be the most potent in terms of binary mixtures. In regard to ternary combinations, Caco-2 cells are more sensitive to the tested mycotoxins, whereas NCI-N87 cells show lower levels of cell damage. Worrying dose reduction values (>10-fold) were found for ENNB in binary and ternary combinations at low exposure levels. These findings are significant for establishing initial reference values, which play a pivotal role in estimating reference doses that are subsequently incorporated into the broader risk assessment process.

Effects of Green Tea Marinade in the Bioaccessibility of Tonalide and Benzophenone 3 in Cooked European Seabass.

Fish consumption is an indicator of human exposure to personal care products (PCP) such as tonalide (AHTN) and benzophenone 3 (BP3). Although most fish consumed is cooked, the impact of cooking procedures on PCP levels is difficult to evaluate. Hence, the aim of this work was to provide thorough information on the stability and bioaccessibility of AHTN and BP3 upon cooking and in vitro digestion. A green tea (Camellia sinensis) marinade, rich in polyphenol, was used as mitigating strategy to reduce these contaminants. Roasting and frying reduced AHTN and BP3 levels in European seabass (Dicentrarchus labrax) spiked samples. Additionally, the green tea marinade promoted a reduction of up to 47% AHTN and 35% BP3. Bioaccessibility of AHTN was higher (up to 45%), and increased with the use of green tea marinades. BP3 showed a bioaccessibility below 19% in all cooked samples. Overall, a decrease in PCP levels was observed after cooking; this decrease was even more pronounced when marination was previously used. However, this decrease is cancelled out by the fact that the bioaccessible fraction of the contaminants increases in an inverse way; therefore, none of these processes can be considered a mitigating alternative.

Occurrence and seasonal variation of several endocrine disruptor compounds (pesticides, bisphenols, musks and UV-filters) in water and sediments from the estuaries of Tagus and Douro Rivers (NE Atlantic Ocean coast).

Exposure of aquatic environments to emerging contaminants is a global issue, special relevant in many estuaries due to impacts from anthropogenic activity. The aim of this work was to evaluate thirty-seven endocrine disruptor chemicals (EDCs) from four different classes (pesticides, bisphenols, polycyclic musks and UV-filters) in water and sediment samples collected during one-year in the estuaries of Tagus and Douro Rivers located into the NE Atlantic Ocean coast. EDCs analysis was achieved afterward validation of a gas-chromatography mass spectrometry (GC-MS) method using Dispersive Liquid-Liquid Microextraction (DLLME) as extraction procedure for water samples, and Quick, Easy, Cheap, Efficient, Rugged and Safe (QuEChERS) combined with DLLME for sediments. Tagus estuary presented higher levels of contamination with pesticide residues and bisphenols (BPs) than the Douro estuary in both water and sediment samples. Contrariwise, levels and frequency of polycyclic musks (PCMs) and UV-filters (UVF) were slightly higher in Douro estuary. Levels of pesticide residues in both sediment and water samples, and levels of PCMs and UVF in water samples were higher in warmer seasons (summer and spring) than in colder ones (winter and autumn). The opposite was found in what respect levels of BPs in water and sediment samples, and PCMs and UVF levels in sediment samples. Although the levels found for each contaminant are low, usually in the order of a few ng/mL(g), the presence of a high number of toxic compounds is a source of concern and requires constant monitoring.

Multi-analyte gas chromatography-mass spectrometry method to monitor bisphenols, musk fragrances, ultraviolet filters, and pesticide residues in seafood.

A gas chromatography-mass spectrometry method for the analysis of thirty-six anthropogenic contaminants in the edible portion of four distinct seafood items is reported. Considering the heterogeneous composition of algae, mussels, and lean/fatty fish muscles, a generic sample preparation based on the QuEChERS procedure combined with dispersive liquid-liquid microextraction (DLLME) with in situ acetylation was successfully applied for quantification of pesticide residues, bisphenols, musk fragrances and UV-filters. Matrix effects were influenced by the type of seafood, with the lowest effects being observed with EMR-lipid and graphitized carbon black sorbents in dispersive solid-phase extraction cleanup step. Method performance features were successful evaluated in the different seafood samples - algae, mussel, lean and fatty fish muscles, following the criteria established by SANTE/12682/2019 for analytical methods for pesticide residues analysis. The detection and quantification of bisphenol F, musk fragrances (galaxolide and tonalide), UV-filters (2-ethylhexyl salicylate, 2-ethylhexyl 4-methoxycinnamate, and isoamyl 4-methoxycinnamate), and residues of permethrin in commercial samples of algae, mussel and fish collected in a Portuguese estuary support the suitability of the proposed method for future seafood monitoring by food safety authorities.

Effect of processing smoked salmon on contaminant contents.

The influence of the type of smoking process (natural/liquid; hot/cold) and salt (NaCl or KCl) on the levels of polybrominated diphenyl ethers (PBDEs) and polycyclic aromatic hydrocarbons (PAHs) in smoked salmon was evaluated. One parent compound - BDE 47 - and two methoxylated forms - 2'-MeO-BDE-68 and 6-MeO-BDE-47 - were detected in all the samples. Among the 14 PAHs analysed, naphthalene was the most abundant followed by phenanthrene and fluorene. Only smoked salmon treated with NaCl presented quantifiable levels of chrysene and benzo[b]fluoranthene. Among the four smoking processes evaluated, natural smoke led to higher levels of PAHs. Risk characterization tools, such as hazard index (HI) and incremental lifetime cancer risk (ILCR), showed that the risk of both PBDEs and PAHs to human health through the consumption of smoked salmon was very low.

A novel dispersive liquid-liquid microextraction using a low density deep eutectic solvent-gas chromatography tandem mass spectrometry for the determination of polycyclic aromatic hydrocarbons in soft drinks.

Ready-to-drink teas can provide, if properly packaged, the taste and wellness character of traditional teas. Nevertheless, in tea processing, there may be several contaminations, among which polycyclic aromatic hydrocarbons (PAHs), anthropogenic contaminants that can present carcinogenic and mutagenic properties. In this work, a novel low-density deep eutectic solvent-based dispersive liquid-liquid microextraction (LDDES-DLLME) procedure followed by gas chromatography tandem mass spectrometry (GC-MS/MS) was optimized for analysis of 15 polycyclic aromatic hydrocarbons (PAHs) in ready-to-drink herbal-based beverages. The new deep eutectic solvent (DES) was synthesized with natural compounds (camphor and hexanoic acid). Several parameters of the extraction procedure such as type and volume of extraction solvent, type, volume of dispersive solvent, and time of extraction were evaluated to achieve the highest yield and to attain the lowest detection limits. The validated method showed very low limits of detection (0.01 µg L-1) and quantification (0.2 µg L-1), good inter- and intra-day precisions (RSD<16.87%), and recoveries higher than 69%. The method was applied to 16 type of samples and it was found total PAHs levels ranging from 0.20 to 1.82 µg L-1. The developed LDDES-DLLME showed a reliable and innovative alternative for the extraction of PAHs from beverages, cost-effective and environmentally friendly, and providing a satisfactory throughput.

Effect of the sodium reduction and smoking system on quality and safety of smoked salmon (Salmo salar).

Excessive sodium (Na) intake has been associated with high blood pressure and cardiovascular diseases. Therefore, sodium reduction is a public health challenge worldwide. The aim of this study was to develop smoked salmon with a reduced Na content. Sodium chloride (NaCl) was replaced by potassium chloride (KCl) at 25% and 50% (molar replacement) and studied in combination with two smoking procedures (natural wood and liquid smoke) as well as two smoking temperatures (18-19 °C or 56 °C). Smoked salmon samples were characterized by physicochemical, sensory and microbiological analyses. No major differences were observed regarding physicochemical properties in the studied treatments. Smoked samples with 50% of NaCl replaced by KCl were slightly more bitter than those with 25% whereas samples with 25% of replacement did not show differences to those with non-reduced Na content (5 g of added NaCl per 100 g of salmon). Molar Na:K ratio decreased from 4,3 in controls to 1,4 and 0,6 in samples with a NaCl reduction level of 25% and 50% respectively. Microbiological assessment indicates that 2-week shelf-life would be appropriate and safe in terms of accomplishment of the EU regulation, taking into account foreseeable storage temperatures (up to 8 °C). Thus, it is possible to achieve a reduction of 25-50% of NaCl in smoked salmon by replacing NaCl by KCl and considerer this product as a "source" of K.

A novel GC-MS methodology to evaluate aromatase activity in human placental microsomes: a comparative study with the standard radiometric assay.

Estrogens are key factors in the development of the estrogen receptor-positive (ER+) breast cancer. Estrogens, estrone (E1), and estradiol (E2) production is achieved by aromatase, a cytochrome P450 enzyme that has androgens, androstenedione (AD), and testosterone (T) as substrates. Nowadays, third-generation aromatase inhibitors (AIs) are considered the gold-standard treatment for ER+ breast cancer in postmenopausal women as well as in premenopausal women with ovary ablation. Aromatase activity assessment still relies on radiometric assays that are expensive, hazardous, and non-environmentally friendly. Thus, in order to overcome these disadvantages, a new methodology was developed to evaluate aromatase activity, based on dispersive liquid-liquid microextraction (DLLME) followed by gas chromatography-mass spectrometry (GC-MS). The enzymatic reaction was carried out in human placental microsomes, using AD as substrate, and the anti-aromatase activity was measured by determining the conversion percentage of AD into E1 (ratio E1/AD) using isotopic analogues as internal standards. The method showed good linearity (r2 = 0.9908 for AD and 0.9944 for E1), high accuracy (more than 74% for AD and more than 66% for E1), high extraction efficiency, and good intra-day and inter-day precision (below 14%, 4 levels). In this work, the IC50 values of the third-generation AIs, anastrozole, letrozole, and exemestane, obtained from the radiometric assay are also compared, and similar IC50 values are described. This method is a good alternative to the current radiometric assay, being fast and sensitive with a good extraction efficiency, accuracy, and recovery. In addition, it may be applied for the evaluation of the anti-aromatase activity of new potential AIs. Graphical abstract.

Green determination of brominated flame retardants and organochloride pollutants in fish oils by vortex assisted liquid-liquid microextraction and gas chromatography-tandem mass spectrometry.

A "green", simple, and low-cost sample extraction procedure involving the use of a deep eutectic solvent (DES) in a vortex assisted liquid-liquid microextraction (VALLME) technique followed by gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis was developed for the simultaneous determination of different PBDEs congeners and OCPs residues in fish oils. After evaluation of different eutectic mixtures, the extraction parameters (volume of DES, amount of oil sample and extraction time) were optimized by means of experimental design in order to maximise extraction efficiency. The developed method was validated in terms of linearity, accuracy and precision, presenting limits of detection in the low ng g-1 level. Its application in the analysis of five fish oil samples, allowed the detection of all the target analytes at levels up 21.5 ng g-1. Fish oils used in animal feed showed to be more contaminated than fish oils for human consumption.

Effects of steaming on contaminants of emerging concern levels in seafood.

Seafood consumption is a major route for human exposure to environmental contaminants of emerging concern (CeCs). However, toxicological information about the presence of CeCs in seafood is still insufficient, especially considering the effect of cooking procedures on contaminant levels. This study is one among a few who evaluated the effect of steaming on the levels of different CeCs (toxic elements, PFCs, PAHs, musk fragrances and UV-filters) in commercially relevant seafood in Europe, and estimate the potential risks associated with its consumption for consumers. In most cases, an increase in contaminant levels was observed after steaming, though varying according to contaminant and seafood species (e.g. iAs, perfluorobutanoate, dibenzo(ah)anthracene in Mytilus edulis, HHCB-Lactone in Solea sp., 2-Ethylhexyl salicylate in Lophius piscatorius). Furthermore, the increase in some CeCs, like Pb, MeHg, iAs, Cd and carcinogenic PAHs, in seafood after steaming reveals that adverse health effects can never be excluded, regardless contaminants concentration. However, the risk of adverse effects can vary. The drastic changes induced by steaming suggest that the effect of cooking should be integrated in food risk assessment, as well as accounted in CeCs regulations and recommendations issued by food safety authorities, in order to avoid over/underestimation of risks for consumer health.

Assessment of multiple mycotoxins in breakfast cereals available in the Portuguese market.

Mycotoxins are secondary metabolites of fungi that cause toxic and carcinogenic effects. Human exposure to multiple mycotoxins constitutes an increasing health concern due to potential mycotoxins combined effects. The presence of mycotoxins mixtures in foodstuffs as cereals has been reported over the last years, but few studies are available concerning its occurrence in cereals primarily marketed for children, a particular vulnerable population group. The present study aims to assess the co-occurrence of twenty-one mycotoxins and metabolites present in breakfast cereals primarily marketed for children in Portugal. Results showed that 96% of the analysed breakfast cereal samples were contaminated with several mycotoxins. Twenty-two combinations were identified including two to seven different mycotoxins. Conclusions pointed out an urgent need to review legislative limits in food matrices consumed by children and to perform a more accurate risk assessment of children's exposure to mycotoxins mixtures in food.

Exploration of the phycoremediation potential of Laminaria digitata towards diflubenzuron, lindane, copper and cadmium in a multitrophic pilot-scale experiment.

The presence of contaminants in aquatic ecosystems can cause serious problems to the environment and marine organisms. This study aims to evaluate the phycoremediation capacity of macroalgae Laminaria digitata for pesticides (diflubenzuron and lindane) and toxic elements (cadmium and copper) in seawater in the presence or absence of mussels. The photosynthetic activity was monitored in the macroalgae to assess its "physiological status". The results showed that the presence of algae decreased diflubenzuron concentration in mussels by 70% after 120 h of exposure. Additionally, this macroalgae was efficient to reduce lindane, Cu and Cd in seawater; even though it not was able to reduce these contaminants in mussels. The studied pollutants did not affect the physiological status of macroalgae. This study reveals that the application of phycoremediation with macroalgae can be an useful and effective mitigation strategy to remove/decrease contaminant levels from the aquatic environment.

Multiclass pesticide analysis in fruit-based baby food: A comparative study of sample preparation techniques previous to gas chromatography-mass spectrometry.

With the aim to develop a new gas chromatography-mass spectrometry method to analyze 24 pesticide residues in baby foods at the level imposed by established regulation two simple, rapid and environmental-friendly sample preparation techniques based on QuEChERS (quick, easy, cheap, effective, robust and safe) were compared - QuEChERS with dispersive liquid-liquid microextraction (DLLME) and QuEChERS with dispersive solid-phase extraction (d-SPE). Both sample preparation techniques achieved suitable performance criteria, including selectivity, linearity, acceptable recovery (70-120%) and precision (⩽20%). A higher enrichment factor was observed for DLLME and consequently better limits of detection and quantification were obtained. Nevertheless, d-SPE provided a more effective removal of matrix co-extractives from extracts than DLLME, which contributed to lower matrix effects. Twenty-two commercial fruit-based baby food samples were analyzed by the developed method, being procymidone detected in one sample at a level above the legal limit established by EU.

New steroidal 17ß-carboxy derivatives present anti-5α-reductase activity and anti-proliferative effects in a human androgen-responsive prostate cancer cell line.

The androgens testosterone (T) and dihydrotestosterone (DHT), besides playing an important role in prostate development and growth, are also responsible for the development and progression of benign prostate hyperplasia (BPH) and prostate cancer. Therefore, the actions of these hormones can be antagonized by preventing the irreversible conversion of T into DHT by inhibiting 5α-reductase (5α-R). This has been a useful therapeutic approach for the referred diseases and can be achieved by using 5α-reductase inhibitors (RIs). Steroidal RIs, finasteride and dutasteride, are used in clinic for BPH treatment and were also proposed for chemoprevention of prostate cancer. Nevertheless, due to the increase in bone and muscle loss, impotency and occurrence of high-grade prostate tumours, it is important to seek for other potent and specific molecules with lower side effects. In the present work, we designed and synthesized steroids with the 3-keto-Δ(4) moiety in the A-ring, as in the 5α-R substrate T, and with carboxamide, carboxyester or carboxylic acid functions at the C-17ß position. The inhibitory 5α-R activity, in human prostate microsomes, as well as the anti-proliferative effects of the most potent compounds, in a human androgen-responsive prostate cancer cell line (LNCaP cells), were investigated. Our results showed that steroids 3, 4 and 5 are good RIs, which suggest that C-17ß lipophylic amides favour 5α-R inhibition. Moreover, these steroids induce a decrease in cell viability of stimulated LNCaP cells, in a 5α-R dependent-manner, similarly to finasteride.

Development of a new gas chromatography-mass spectrometry (GC-MS) methodology for the evaluation of 5α-reductase activity.

The androgens testosterone (T) and dihydrotestosterone (DHT) play a key role in the function and integrity of prostate tissue, but are also implicated in prostate cancer and benign prostatic hyperplasia (BPH). The reduction of androgen levels can be achieved by the inhibition of 3-oxo-5α-steroid-4-dehydrogenase (5α-reductase), which is responsible for the irreversible conversion of T into its more active metabolite DHT. In fact, the use of 5α-reductase inhibitors (RIs), like finasteride, can be a valuable strategy for the treatment of BPH and in chemoprevention of prostate tumors. In this work a new method based on a dispersive liquid-liquid microextraction (DLLME) procedure, followed by gas chromatography-mass spectrometry (GC-MS), to evaluate the 5α-reductase activity, by measuring the conversion percentage of T into DHT was optimized and validated. Enzymatic assays were carried out in human prostate microsomes, using T as substrate. T and DHT were extracted by the developed DLLME technique and quantified, after silylation, by GC-MS. Variables affecting the extraction efficiency and derivatization of T and DHT were evaluated. The optimized method showed good linearity (with correlation coefficients over 0.9994 for T and 0.9995 for DHT), good recoveries (higher than 80%), and good intra- and inter-day precision (below 13%, 3 levels, n=6). The detection limits for T and DHT were 0.5 nM and the limits of quantification were 5 nM. The new GC-MS method is a good alternative to the already described methods, to evaluate 5α-reductase activity, since it avoids the use of radioactive compounds and corresponds to a fast and sensitive methodology with a good extraction efficiency, accuracy and high recovery. As this method allows the evaluation of 5α-reductase activity, also permits the study of inhibitory efficacy of new molecules as potential RIs.

Determination of phosmet and its metabolites in olives by matrix solid-phase dispersion and gas chromatography-mass spectrometry.

An accurate method based on matrix solid-phase dispersion (MSPD), and gas chromatography-mass spectrometry (GC/MS) was developed for determination of phosmet residues and its metabolites (phosmet-oxon, phthalimide, N-hydroxymethylphthalimide, and phthalic acid) in olive fruits. After testing different sorbents and eluents for MSPD extraction, C(18) and acetonitrile were found to be the most appropriate for clean-up of the samples, in terms of yields and efficient removal of interfering compounds. All analytes were determined in selective ion monitoring (SIM) mode following a derivatization step with N,O-bis-trimethylsilyltrifluoroacetamide (BSTFA) containing 1% of trimethylchlorosilane (TMCS), except for phosmet and phosmet-oxon which were analyzed directly. The method showed suitable linearity (correlation coefficients higher than 0.8919 for all the compounds) and suitable sensitivity (limit of detection lower than 0.06mg/kg). It was successfully applied in the analysis of olive fruits collected during the preharvest interval and olive oil. Phosmet residues found in all samples were lower than the maximum residue limits established by legislation (2mg/kg).

Quantification of free and esterified sterols in Portuguese olive oils by solid-phase extraction and gas chromatography-mass spectrometry.

A simple and accurate method based on solid-phase extraction (SPE), transesterification and gas chromatography-mass spectrometry (GC-MS) was developed for the quantitative analysis of free and esterified sterols of olive oil. In order to achieve better separation of esterified and free sterols, silica and alumina SPE adsorbents were tested. Separations by silica provided more reproducible results. The transesterification of both sterol fractions was found to be more user friendly than saponification as a method to liberate the sterols from the respective esters. The free sterols were then silylated with N,O-bis-trimethylsilyltrifluoroacetamide (BSTFA) with 1% of trimethylchlorosilane (TMCS). The most favourable conditions for exploitation of this reagent were established. The optimized methodology was suitable for evaluation of free and esterified sterols in Protected Designation of Origin (PDO) olive oils and monovarietal olive oils with different maturation indices. The prevailing phytosterols in all olive oils were beta-sitosterol and campesterol. The free sterols predominated, although they seemed to decrease with the maturation of the olive fruits.