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  • Amino acids and biogenic amines evolution during the estufagem of fortified wines
    Publication . Pereira, Vanda; Pereira, Ana C.; Pérez Trujillo, Juan P.; Cacho, Juan; Marques, José C.
    The current study was focused on the impact of accelerated ageing (heating step) on the amino acid and biogenic amine profiles of fortified wines. In this sense, three Madeira wines from two commonly used grape varieties (one red and the other white) were analysed during the heating, at standard (45∘ C, 3 months) and overheating (70∘ C, 1 month) conditions, following a precolumn derivatization procedure using iodoacetic acid, o-phthaldialdehyde, and 2-mercaptoethanol, carried out in the injection loop prior to RP-HPLC-FLD detection. Eighteen amino acids were identified, with arginine being the most abundant. An important decrease of the amino acid levels was detected during the standard heating (up to 30%), enhanced up to 61% by the temperature increase. Cysteine, histidine, and asparagine revealed the greatest decreases at 45∘ C. Conversely, some amino acids, such as asparagine, slightly increased. Four biogenic amines were identified but always in trace amounts. Finally, it was observed that the accelerated ageing did not favour the biogenic amine development. The results also indicate that the heating process promotes the amino acid transformation into new ageing products.
  • A sensitive method for the rapid determination of underivatized ethyl carbamate in fortified wine by liquid chromatography-electrospray tandem mass spectrometry
    Publication . Leça, João M.; Pereira, Vanda; Pereira, Ana C.; Marques, José C.
    This work presents the optimization of a miniaturized liquid-liquid extraction (mLLE) followed by reversed-phase liquid chromatography-electrospray tandem mass spectrometry (RP-HPLC-MS/MS) for the determination of ethyl carbamate (EC) in fortified wine, without using derivatizing agents. The mLLE was optimized by an experimental design. Thus, 15 mL of wine and 8 mL of ethyl acetate were used for the extraction. After concentration, each extract was injected into the HPLC MS/MS equipment and the characteristic secondary ion transition of EC (m/z = 90.10 → 62.05) was used for the quan tification purposes. The proposed method presented a good lin earity (R2 = 0.9999) and a high sensitivity with low limits of detection (LOD) and quantification (LOQ), 0.17 and 0.52 μg L−1 , respectively. The precision (repeatability and reproducibility) never exceeded 8% of variation, and the recoveries varied between 93 and 114%. The applicability of the method was checked through the analysis of 24 fortified wines, with EC values ranging between 23 ± 1 and 194 ± 5 μg L−1 . All chromatograms revealed good peak resolutions. This new method is efficient for the simple, fast, and reliable determination of EC in fortified wines, providing great sensitivity without using derivatizing agents or large volumes of organic solvents.
  • Unveiling the evolution of Madeira Wine key metabolites: a three-year follow-up study
    Publication . Pereira, Vanda; Leça, João M.; Freitas, Ana I.; Pereira, Ana C.; Pontes, Marisela; Albuquerque, Francisco; Marques, José C.
    Madeira wine (MW) encompasses an unusual oxidative ageing process that makes it distinc tive. Several metabolites have been related to its quality and safety, such as 5-hydroxymethylfurfural (HMF), furfural, sotolon, and ethyl carbamate (EC). These compounds were quantified over a three year period to assess their formation rate according to the ageing procedure used: canteiro vs. estufagem. Estufagem, which includes thermal processing of young MWs, promoted greater HMF, furfural, and sotolon accumulation, especially in sweet wines, in which sotolon contributed significantly to aroma (odour active values up to 17.5). Tinta Negra revealed a higher predisposition to form EC while Malvasia and Sercial were less prone to its formation. The formation of furfural, HMF, and EC strongly correlated with the ageing time. Sotolon had a strong correlation with the ageing time in canteiro (r = 0.79) and a moderate correlation in estufagem (r = 0.65). In both ageing procedures, sotolon, furfural, and HMF formation trends strongly correlated with each other (r = 0.74–0.90). In turn, EC also correlated with all furans (r = 0.51–0.85). Yellow tones (b*) correlated with these metabolites only when wines undergo estufagem. This study provides valuable insights to improve MW quality and safety management procedures.
  • Evaluation of fucoxanthin contents in seaweed biomass by vortex-assisted solid-liquid microextraction using high-performance liquid chromatography with photodiode array detection
    Publication . Nunes, N.; Leça, João M.; Pereira, Ana C.; Pereira, Vanda; Ferraz, S.; Barreto, Maria Carmo; Marques, José C.; Carvalho, M.A.A. Pinheiro de
    Fucoxanthin is considered an important marine bioactive compound with biological properties with promising effects, namely on health. A simple and efficient analytical methodology is proposed for its quantification in seaweed biomass by using vortex-assisted solid-liquid microextraction (VASLME) followed by reversed phase high-performance liquid chromatography (RP-HPLC) photodiode array detection (PDA) analysis. This microextraction uses reduced quantities of sample (25 mg) and solvent (300 μL of ethanol) to efficiently extract this high-valued xanthophyll, in a vortex time of 15 min. These extraction parameters were optimized performing a Central Composite Design (CCD) analysis, running 32 individual experiments. In turn, the method validation was assessed. The linearity of the method was confirmed (R2 = 0.99998) in a concentration range from 12 to 3600 μg·g−1 dw. Also, good sensitivity and accuracy results were observed through the LOD (3.33 μg·g−1 ), LOQ (10.09 μg·g−1 ) and recovery (varied from 95 to 97%) assessments. Good precision was also verified, with intra-day variation within 2.0–3.3%, and inter-day within 1.0–3.8%. Matrix effect was also evaluated and an acceptable variation of 3.4% was found. The method applicability was confirmed by the analysis of 22 seaweed biomass samples and fucoxanthin content was found to vary from about 10 to 853 μg·g−1 dw. This method demonstrated a good performance and can be successfully implemented for a rapid, reliable and accurate screening of fucoxanthin in seaweed biomass.
  • Modelling the ageing process: a novel strategy to analyze the wine evolution towards the expected features
    Publication . Pereira, Ana C.; Carvalho, Maria J.; Miranda, Andreia; Leça, João M.; Pereira, Vanda; Albuquerque, Francisco; Marques, José C.; Reis, Marco S.
    In this work we present a new strategy to monitor the wine evolution during the ageing process. More specifi cally, we validate a procedure for analyzing how wine evolves during the ageing process in relation to the desired and expected quality features and we apply the proposed methodology to the case of a Portuguese fortified wine, the Madeira wine, where we compare the wine evolution under two different ageing processes. The approach developed consists on modeling samples labeled as aged reference wines (5 year old Madeira wines), produced from four different grape varieties, and then analyze how and in which extent young wines (up to 3 years old) come closer to the reference data set. The analysis is based on a comprehensive set of chemical data, including: polyphenolic composition, organic acids, reducing sugars, color and oenological parameters, commonly used as routine quality control information. The study considers several feature extraction methods, such as: Principal Components of Analysis (PCA), Independent Component of Analysis (ICA) and Partial Least Squares (PLS). The classification methodologies tested were: Linear Discriminant Analysis (LDA), nearest neigh bor (k-NN) and Soft Independent Modelling by Class Analogy (SIMCA). The different options of preprocessing/ feature extraction/classification were evaluated and compared using a Monte Carlo approach. From our analysis, the best combination of feature extraction/classification methodologies was PLS/LDA, which presented a classification performance of approximately 90% for three out of the four classes modeled, and of about 78% for the remaining one. Regarding the wines monitored during the first 3 years, our analysis revealed that they indeed mature in relation to the five year old reference wines. Furthermore, for some wines, it is possible to detect differences between the two ageing processes analyzed. This study is of particular importance for this type of wines, where the ageing process plays a central role for attaining the expected quality levels, implying significant risks and costs for local and industrial producers. Notwithstanding the specific case study presented, the strategy outlined can be extrapolated to other products with similar characteristics in terms of their monitoring and process control
  • A simple emulsification-assisted extraction method for the GC–MS/SIM analysis of wine markers of aging and oxidation: application for studying micro-oxygenation in Madeira Wine
    Publication . Freitas, Ana I.; Pereira, Vanda; Leça, João M.; Pereira, Ana C.; Albuquerque, Francisco; Marques, José C.
    Sotolon and the heterocyclic acetals of glycerol are known as potential aging and oxidation markers in fortified wines such as Madeira, Port, and Sherry. Thus, determining the evolution of these compounds under different oxidative aging conditions is important for fortified wine quality purposes. This study proposes a new methodology based on a miniaturized emulsification extraction followed by GC–MS/SIM, which was developed and optimized to follow the formation of sotolon and heterocyclic acetals in fortified wines that were submitted to traditional accelerated aging and micro-oxygenation. The optimization was achieved by means of a mixed-level factorial design, considering 3 factors: sample volume, extractant volume, and concentrated extract volume, by performing 19 experiments in duplicate. The extraction was optimized using 8 mL of wine sample, 5 mL of dichloromethane, concentrating the extract up to 10-fold. The method performance was evaluated for sotolon, using a matrix matched calibration between 10 and 2000 μg/L. The selectivity was confirmed through the analysis of real samples. The methodology showed good linearity (R2 = 0.999), high sensitivity (LOQ = 6.8 μg/L), recovery about 105%, and good precision (less than 8 and 9%, evaluated by the variation of intra- and inter-day measurements, respectively). This is the first methodology that revealed to be an excellent tool to simultaneously follow the formation of sotolon and heterocyclic acetals in Madeira wines, using an inexpensive, simple, efficient, and effective experimental layout. Indeed, it was shown that traditional accelerated aging and micro-oxygenation have impact on the formation of such molecules.
  • Evaluation of wine colour under accelerated and oak-cask ageing using CIELab and chemometric approaches
    Publication . Carvalho, Maria João; Pereira, Vanda; Pereira, Ana C.; Pinto, João L.; Marques, José C.
    The present study aims to analyse the evolution of colour and browning of fortified wines submitted to oak and accelerated ageing induced by temperature, both traditional ageing processes of Madeira wines. These wines were follow ed during the first 2 years of ageing and were simultaneously compared to aged reference samples, in order to disclose if accelerated ageing favours the wine evolution. The data anal ysis approaches followed two strategies: the first one was based on the monitoring of wine colour parameters based on CIELab methodology, while the second strategy adopted an untargeted approach, taking advantage of all wine information comprised on the UV-vis spectrum. CIELab results indicated that the greatest variation (up to 92 %) occurs during the vinification, since it was observed that wines produced from the same grape variety (Tinta Negra) acquired different char acteristics already on the vinification processes. All wines tend to approach the reference samples during ageing, with the lowest ΔE* value obtained for Malvasia submitted to canteiro at 2 years of ageing (3.29 units). Sweet Tinta Negra wines, previously submitted to estufagem, presented the most pronounced colour change associated with ageing. The multi variate principal component analysis (PCA) model was built with aged reference samples to evaluate how young wines acquire the reference wine’s characteristics and revealed that accelerated ageing increases colour evolution and favours the homogeneity of Malvasia wines.
  • Rapid determination of sotolon in fortified wines using a miniaturized liquid-liquid extraction followed by LC-MS/MS analysis
    Publication . Pereira, Vanda; Leça, João M.; Gaspar, João M.; Pereira, Ana C.; Marques, José C.
    Sotolon (4,5-dimethyl-3-hydroxy-2,5-dihydrofuran-2-one) is a powerful odorant usually pointed out as being responsible not only for the characteristic curry notes of the finest fortified wines but also for the off-flavour notes in prematurely oxidized white wines. Most methods reported in literature for quantifying sotolon in wines are quite laborious and use large volumes of organic solvents. *us, in the present study, the development of a simple, fast, and environment-friendly method for the quantification of sotolon in fortified wine is herein presented. *e proposed method uses a single-step liquid-liquid extraction followed by RP-LC MS/MS and was optimized using a full factorial design. *e method showed good linearity (R2 � 0.9999), intra- and interday precision lower than 10% RSD, recovery of about 95%, and high sensitivity (LOQ of 0.04 μg/L). *e method was applied to analyse 44 fortified wines from different styles (from dry to sweet wines) and ages (3–115 years old), and it was found that it covers the concentration range usually found for this compound in this kind of alcoholic beverages, which was found to be within 6.3–810 μg/L. *us, it can be concluded that this method can be used as an accurate tool for the rapid analysis of sotolon, since the early stages of its formation up to long ageing periods.
  • Rapid and sensitive methodology for determination of ethyl carbamate in fortified wines using microextraction by packed sorbent and gas chromatography with mass spectrometric detection
    Publication . Leça, João M.; Pereira, Vanda; Pereira, Ana C.; Marques, José C.
    This work presents a new methodology to quantify ethyl carbamate (EC) in fortified wines. The presented approach combines the microextraction by packed sorbent (MEPS), using a hand-held automated ana lytical syringe, with one-dimensional gas chromatography coupled with mass spectrometry detection (GC–MS). The performance of different MEPS sorbent materials was tested, namely SIL, C2, C8, C18, and M1. Also, several extraction solvents and the matrix effect were evaluated. Experimental data showed that C8 and dichloromethane were the best sorbent/solvent pair to extract EC. Concerning solvent and sample volumes optimization used in MEPS extraction an experimental design (DoE) was carried out. The best extraction yield was achieved passing 300 L of sample and 100 L of dichloromethane. The method validation was performed using a matrix-matched calibration using both sweet and dry fortified wines, to minimize the matrix effect. The proposed methodology presented good linearity (R2 = 0.9999) and high sensitivity, with quite low limits of detection (LOD) and quantification (LOQ), 1.5 g L−1 and 4.5 g L−1, respectively. The recoveries varied between 97% and 106%, while the method precision (repeatability and reproducibility) was lower than 7%. The applicability of the methodology was confirmed through the analysis of 16 fortified wines, with values ranging between 7.3 and 206 g L−1. All chromatograms showed good peak resolution, confirming its selectivity. The developed MEPS/GC–MS methodology arises as an importanttoolto quantify EC in fortified wines, combining efficiency and effectiveness, with simpler, faster and affordable analytical procedures that provide great sensitivity without using sophisticated and expensive equipment.