Loading...
6 results
Search Results
Now showing 1 - 6 of 6
- Volatile sulphur compounds composition of monovarietal white winesPublication . Moreira, Nathalie; Pinho, Paula Guedes de; Santos, Cristina; Vasconcelos, IsabelThe sulphur compounds composition of wines produced experimentally from six white cultivars (Alvarinho, Loureiro, Trajadura, Pedernã, Azal Branco and Avesso) was evaluated during two consecutive vintages. Results show that wines could be differentiated according to their sulphur compounds content. In general, Loureiro, Trajadura and Pedernã cultivars led to wines with low concentrations of sulphur compounds; however, Loureiro wines were characterised by significant amounts of dimethyl sulphone, whereas Trajadura wines possessed a high content of 3-(methylthio)propyl acetate and 4-(methylthio)-1-butanol. Alvarinho and Avesso wines showed high levels of S-methyl thioacetate, 3-mercapto-1-propanol, 3-(ethylthio)-1-propanol and 3-methylthiopropionic acid. Significant amounts of 2-methyltetrahydrothiophen-3-one, cis- and trans-2-methyltetrahydrothiophen-3-ol were also found in Avesso wines. Azal Branco wines were low in 3-(methylthio)propyl acetate and 2-(methylthio)ethanol, and high contents in S-methyl thioacetate, 3-mercapto-1-propanol and 2-mercaptoethanol. A linear discriminant analysis of sulphur compounds levels showed a differentiation of wines according to their varietal origin.
- Sensory attributes and volatile composition of a dry white wine under different packing configurationsPublication . Moreira, N.; Lopes, P.; Ferreira, H.; Cabral, M.; Pinho, P. Guedes deThe aim of this work was to study the effect of different configurations of packaging on the volatile composition and sensory properties of a white wine. Certain oenological parameters were also evaluated. Bag-in-box (BIB) and glass bottles sealed with two different cork stoppers, natural and Neutrocork (technical), were used in the experiments. Analysis were carried out before packaging and after 3, 6 and 12 months of storage. Results showed that wines packaged in BIB presented higher levels of brown color than wines in bottles sealed with corks. In all packaging configurations, the content of free SO2 decreased with storage time; however, BIB wines showed a lower content of free SO2 than bottle wines during 12 months. Moreover, wines under BIB presented a significant lower amount of 2-phenylethanol, 2-phenylethyl acetate, isoamyl acetate, ethyl butanoate, ethyl hexanoate, ethyl octanoate, linalool and b-damascenone than bottled wines.
- Non-targeted and targeted analysis of wild toxic and edible mushrooms using gas chromatography–ion trap mass spectrometryPublication . Carvalho, Luís Miguel; Carvalho, Félix; Bastos, Maria de Lourdes; Baptista, Paula; Moreira, Nathalie; Monforte, Ana Rita; Silva, Ferreira António César; Pinho, Paula Guedes deMushrooms are known all over the world both due to the remarkable gastronomic value of some species and for severe intoxications mediated by other species that are frequently difficult to distinguish from the edible ones, by the common user. Therefore, it is important to develop strategies to discover molecules that can identify mushroom species. In the present work, two GC-MS methodologies were applied in the chemical characterization of 22 mushroom species (12 edible, 3 toxic and 7 potentially toxic) - a multi-target procedure to simultaneously determine amino acids (AA), fatty acids (FA) and sterols by previous derivatization procedure with MSTFA, and a Head Space-Solid Phase Microextraction method to determine volatiles. For both methods, two approaches to data analysis were used: (I) targeted analysis, to identify and quantify AA, FA sterols and volatiles; (II) untargeted analysis, including Principal Component Analysis and Partial Least Square Discriminant Analysis, in order to identify metabolites/metabolite pattern with potential species identification and/or differentiation. Multi-target experiment allowed the identification and quantification of twenty one primary metabolites (9 AA, 11 FA and 1 sterol). Furthermore, through untargeted data analysis, it was possible to identify a 5-carbon sugar alcohol structure molecule, which was tentatively identified as xylitol or adonitol, with potential to be a species-marker of the edible Suillus bovinus mushrooms. Volatile profiling studies resulted in the identification of the main volatiles in mushrooms. Untargeted analysis allowed the identification of 6 molecules that can be species- or genus-specific: one secondary metabolite specific to the edible species Lycoperdon perlatum, an ester of hexanoic acid, tentatively identified as allyl or vinyl caproate; and five other secondary metabolites, whose identification was not achieved, which were only detected in Lactarius aurantiacus specimens (edibility/toxicity unknown).
- Optimisation and validation of a HS-SPME-GC-IT/MS method for analysis of carbonyl volatile compounds as biomarkers in human urine: Application in a pilot study to discriminate individuals with smoking habitsPublication . Calejo, Isabel; Moreira, Nathalie; Araújo, Ana Margarida; Carvalho, Márcia; Bastos, Maria de Lourdes; Pinho, Paula Guedes deA new and simple analytical approach consisting of an automated headspace solid-phase microextraction (HS-SPME) sampler coupled to gas chromatography-ion trap/mass spectrometry detection (GC–IT/MS) with a prior derivatization step with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) was developed to detect volatile carbonyl metabolites with low molecular weights in human urine. A central composite design (CCD) was used to optimise the PFBHA concentration and extraction conditions that affect the efficiency of the SPME procedure. With a sample volume of 1 mL, optimal conditions were achieved by adding 300 mg/L of PFBHA and allowing the sample to equilibrate for 6 min at 62 °C and then extracting the samples for 51 min at the same temperature, using a divinylbenzene/polydimethylsiloxane (DVB/PDMS) fibre. The method allowed the simultaneous identification and quantification of 44 carbonyl compounds consisting of aldehydes, dialdehydes, heterocyclic aldehydes and ketones. The method was validated with regards to the linearity, inter- and intra-day precision and accuracy. The detection limits ranged from 0.009 to 0.942 ng/mL, except for 4-hydroxy-2-nonenal (15 ng/mL), and the quantification limits varied from 0.029 to 1.66 ng/mL, except for butanal (2.78 ng/mL), 2-butanone (2.67 ng/mL), 4-heptanone (3.14 ng/mL) and 4-hydroxy-2-nonenal (50.0 ng/mL). The method accuracy was satisfactory, with recoveries ranging from 90 to 107%. The proof of applicability of the methodology was performed in a pilot target analysis of urine samples obtained from 18 healthy smokers and 18 healthy non-smokers (control group). Chemometric supervised analysis was performed using the volatile patterns acquired for these samples and clearly showed the potential of the volatile carbonyl profiles to discriminate urine from smoker and non-smoker subjects. 5-Methyl-2-furfural (p<0.0001), 2-methylpropanal, nonanal and 2-methylbutanal (p<0.05) were identified as potentially useful biomarkers to identify smoking habits.
- Development and optimization of a HS-SPME-GC-MS methodology to quantify volatile carbonyl compounds in Port winesPublication . Moreira, Nathalie; Araújo, Ana Margarida; Rogerson, Frank; Vasconcelos, Isabel; Freitas, Victor de; Pinho, Paula Guedes deA method based on headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography-triple quadrupole/mass spectrometry detection (GC-TQ/MS) with a prior derivatization step with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) was developed to quantify carbonyl compounds in different categories of Port wines. Optimal extraction conditions were obtained incubating 2 ml of wine with 2.3 g/l of PFBHA for 10 min and extracted during 20 min at 32 °C. The method was validated for 38 carbonyl compounds (alkanals, alkenals, Strecker aldehydes, dialdehydes, ketones and furan aldehydes) with regard to linearity, repeatability, inter and intra-day precision and accuracy, showing that the method is suitable for the determination of carbonyl compounds in wines. Tawny wines with ‘indication of age’ (10–40 years old) presented the highest levels of some carbonyl compounds, such as propanal, pentanal, hexanal, Strecker aldehydes, diacetyl, methyl glyoxal, 3-pentanone and 2-furfural, whereas Ruby wines were characterized by the highest amounts of some unidentified compounds.
- HS-SPME/GC-MS methodologies for the analysis of volatile compounds in cork materialPublication . Moreira, Nathalie; Lopes, P.; Cabral, M.; Pinho, P. Guedes deTwo methods based on headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography– ion trap mass spectrometry (GC-IT/MS) were proposed for the analysis of volatile organic compounds (VOCs) in cork material used in the production of cork stoppers. The effect of various factors affecting the extraction efficiency was carried out by means of a 24 full factorial design. The first method allowed the extraction of 17 terpenes by using a divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber (50/30 μm). The optimal conditions were achieved when cork extract (5 mL) added with 2.3 g of NaCl was extracted during 35 min at 55 °C. The second method allowed the identification of 41 carbonyl compounds after in-solution (5 mL) derivatization with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA, 2.3 mg/mL), followed by an incubation period of 6 min at 52 °C and extraction during 36 min at the same temperature, using a PDMS/DVB (50/30 μm) fiber. Both methods are simple, solvent free and fast. These methods were applied to the analysis of different cork raw material showing significant differences in the amounts of volatile compounds analyzed. Alcanfor and α-terpineol were the terpenes compounds present at highest amounts, and within carbonyl compounds analyzed, some samples presented a high level of butanal, octanal, nonanal, and glyoxal.