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- 3-Hydroxy-4,5-dimethyl-2(5H)-furanone levels in fortified Madeira wines: relationship to sugar contentPublication . Câmara, José sousa; Marques, José C.; Alves, Maria A.; Ferreira, António C. SilvaThe maturation of Madeira wines usually involves exposure to relatively high temperatures and humidity levels >70%, which affect the aroma and flavor composition and lead to the formation of the typical and characteristic bouquet of these wines. To estimate the levels of sotolon [3-hydroxy-4,5-dimethyl-2(5H)-furanone] and their behavior over time, 86 aged Madeira wines samples (1−25 years old), with different sugar concentrations, respectively, 90 g L-1 for Boal, 110 g L-1 for Malvazia, 25 g L-1 for Sercial, and 65 g L-1 for Verdelho varieties, were analyzed. Isolation was performed by liquid−liquid extraction with dichloromethane followed by chromatographic analysis by GC-MS. The reproducibility of the method was found to be 4.9%. The detection and quantification limits were 1.2 and 2.0 μg L-1, respectively. The levels of sotolon found ranged from not detected to 2000 μg L-1 for wines between 1 and 25 years old. It was observed that during aging, the concentration of sotolon increased with time in a linear fashion (r = 0.917). The highest concentration of sotolon was found in wines with the highest residual sugar contents, considering the same time of storage. The results show that there is a strong correlation between sotolon and sugar derivatives: furfural, 5-methylfurfural, 5-hydroxymethylfurfural, and 5-ethoxymethylfurfural. These compounds are also well correlated with wine aging. These findings indicate that the kinetics of sotolon formation is closely related with residual sugar contents, suggesting that this molecule may come from a component like sugar.
- 3-Hydroxy-4,5-dimethyl-2(5H)-furanone: a key odorant of the typical aroma of oxidative aged Port WinePublication . Ferreira, A. C. Silva; Jean-Christophe, Barbe; Bertrand, AlainApplication of aroma extract dilution analysis (AEDA) on organic extracts from Port wines barrel-aged over 40 years revealed 5 odor-active compounds corresponding to descriptors used to qualify the characteristic old wine aroma. One of the compounds, described as “nutty” and “spicy-like”, and present in at least 9 dilutions above the others, was perceived as particularly important. The compound responsible for this flavor was identified as 3-hydroxy-4,5-dimethyl-2(5H)-furanone (sotolon). The levels ranged from 5 to 958 μg/L for wines between 1 and 60 years old. It was also observed that during oxidative aging the concentration of this compound increased with time according to a linear trend (r > 0.95). Although the presence of 2-ketobutyric acid was verified, the constant rate of formation of sotolon with aging and its high correlation with sugar derivates (HMF, furfural) suggests other mechanisms, different from those reported for other wines. The flavor threshold of sotolon was evaluated in Port wine at 19 μg/L. Sensorial tests provided valuable information concerning sotolon impact on Port wine aroma. Samples supplemented with this substance were consistently ranked as older. In view of these results it can be expected that sotolon plays a pre-eminent role in the characteristic old Port wine aroma.
- 4-Chlorophenol degradation by a bacterial consortium: development of a granular activated carbon biofilm reactorPublication . Caldeira, M.; Heald, S. C.; Carvalho, M. F.; Vasconcelos, I.; Bull, A. T.; Castro, P. M. L.A bacterial consortium that can degrade chloro- and nitrophenols has been isolated from the rhizosphere of Phragmitis communis. Degradation of 4-chlorophenol (4-CP) by a consortium attached to granular activated carbon (GAC) in a biofilm reactor was evaluated during both open and closed modes of operation. During the operation of the biofilm reactor, 4-CP was not detected in the column effluent, being either adsorbed to the GAC or biodegraded by the consortium. When 4-CP at 100 mg l−1 was fed to the column in open mode operation (20 mg g−1 GAC total supply), up to 27% was immediately available for biodegradation, the rest being adsorbed to the GAC. Biodegradation continued after the system was returned to closed mode operation, indicating that GAC bound 4-CP became available to the consortium. Biofilm batch cultures supplied with 10–216 mg 4-CP g−1 GAC suggested that a residual fraction of GAC-bound 4-CP was biologically unavailable. The consortium was able to metabolise 4-CP after perturbations by the addition of chromium (Cr VI) at 1–5 mg l−1 and nitrate at concentrations up to 400 mg l−1. The development of the biofilm structure was analysed by scanning electron microscopy and confocal laser scanning microscopy (CLSM) techniques. CLSM revealed a heterogeneous structure with a network of channels throughout the biofilm, partially occupied by microbial exopolymer structures.
- a* values to follow lycopene concentration during ripening and storage of tomato (cv. Caruso)Publication . Schauwers, Axelle; Rocha, Ada M. C. N.; Morais, Alcina M. M. B.The ripening of tomato fruit is a highly regulated process during which colour, flavour, aroma and texture change in a coordinated manner. This research work aims to correlate the colour changes measured objectively with the lycopene concentration in tomatoes during ripening at room temperature (21 and 26°C). These results were compared with colour and lycopene content of pink and light red tomatoes stored at 14°C, temperature used to prevent ripening and therefore extend the shelf life of the fruits. The duration of heat treatment at 100ºC was previously optimized in order to release the maximum lycopene from chromoplasts during extraction. An a* value of 20 for the peel corresponds to an increase of lycopene content of Caruso tomato from 9 to 43 mg/100 g TSS, at room temperature. The shelf life of pink and light red tomatoes can be extended to two weeks at 14ºC without loss of lycopene content, presenting the same content as green tomatoes ripened at room temperature for one week.
- Ability of lactic acid bacteria to produce volatile phenolsPublication . Couto, José A.; Campos, Francisco M.; Figueiredo, Ana R.; Hogg, Tim A.Thirty-live strains of lactic acid bacteria (20 species) were screened for the ability to produce volatile phenols from the corresponding phenolic acids, p-coumaric and ferulic, in culture medium. The concentration of vinylphertols and ethylphenols in the growth mediuro was analyzed by gas chromatography. Results showed that 13 strains t3?%) were able to produce volatile phenols from p-coumaric acid, although only three (9%) produced 4-ethylphcnnl. the final product of the p-coumnric acid metabolic pathway. The reduction step of this pathway was only l`ound in the Lactobacillus genus: L brevis, L. cotlinoider, and L plnntnrttrrt. Seven of the eight pediococci strains studied were able to produce 4-vinylphenol but not 6-ethylphenol from p-coumaric acid. The two Oenococcus nent strains und the strain of Leuconostoc rneseitterriirler studied did ROI produce either of the two p-coumaric acid derivatives. Strains that produced volatile phenols were used in subsequent studies at lower phenolic acid con-centrations. Experiments with added 5 mgfL oi`p-cottniaric acid showed that some strains can still produce re1atively high (up to S00 ugiL) concentrations of 4-ethylphenol. The capacity of lactic acid bacteria to produce volatile phenols from l`crulic acid was much lower than its capacity to produce volatile phcrtols from pecouniaric acid.
- Accelerated life testing of frozen green beans (Phaseolus vulgaris, L.) quality loss kinetics: colour and starchPublication . Martins, R. C.; Lopes, I. C.; Silva, C. L. M.This study uses the information derived from a computational research for the design of accelerated life testing (ALT) to implement experimentally the step stress methodology for the quantification of frozen green beans (Phaseolus vulgaris, L.) colour and starch degradation kinetics. Colour loss and starch degradation were successfully modelled, respectively, by a first-order reversible and apparent first-order kinetics, under dynamic temperature fluctuations. Results show that the step stress produces models with lower regression standard errors than the conventional isothermal methodology, increasing the accuracy of the estimated kinetic parameters. The ALT methodology, produces however, higher confidence intervals for the estimated kinetic parameters, than the isothermal methodology (e.g. colour b-coordinate by the: (i) isothermal methodology: k₋₁₅ ºC=22.189±0.349 day⁻¹·10⁻³; and (ii) ALT methodology: k₋₁₅ ºC=22.189±0.349 day⁻¹·10⁻³). Furthermore, as expected, higher Arrhenius activation energies (Ea) were estimated by the ALT step-stress methodology, than by the isothermal methodology (e.g. Hunter total colour difference (TCDH): (i) isothermal methodology: Ea=106.272±18.67 kJmol⁻¹; and (ii) ALT methodology: Ea=140.344±18.670 kJmol⁻¹). Accelerated tests are valuable tools, that can aid the study of quality losses in frozen foods. Although ALT tests increase the complexity of data analysis, they produce satisfactory results, when applied to frozen green beans kinetics of starch and colour losses.
- Action of cardosin A from Cynara humilis on ovine and caprine caseinatesPublication . Silva, Sofia V.; Malcata, F. XavierIn the Iberian Peninsula, the proteinases present in the flowers of members of the Cynara genus, C. cardunculus, C. humilis and C. scolymus, have for many years been successfully used in the manufacture of traditional cheeses from ovine and/or caprine milk on individual farms (Vieira de Sá & Barbosa, 1972; Trujillo et al. 1994). In Portugal, C. cardunculus is the species most frequently employed. Although commercial thistle was tentatively assumed to be pure in taxonomic terms, accurate analyses have shown that the flowers of C. cardunculus are often mixed with flowers of C. humilis (Pires et al. 1994). The clotting activity of C. humilis is due to an aspartic proteinase, currently designated cardosin A and similar to another enzyme obtained from C. cardunculus. This enzyme is similar in specificity and activity to chymosin (Pires et al. 1994). The action of cardosin A from C. cardunculus upon ovine and caprine caseins has been reported recently (Ramalho-Santos et al. 1996; Simo4es, 1998; Sousa & Malcata, 1998), but as yet there is no information on the proteolytic activity of the proteinase from C. humilis upon caseins from milks other than bovine. Caseins from small ruminants' milks are the usual substrates of cardosin during milk coagulation and cheese ripening, and sodium caseinate represents an intermediate system between isolated caseins and the cheese matrix that is free from interference by fat. Thus ovine and caprine caseinates may be useful substrates for investigating the proteolytic activity of cardosin. The aim of the present study was to compare the action of pure cardosin A, obtained from C. humilis, on caprine and ovine caseinates, and to assess the in vitro contribution of this enzyme to the overall proteolytic action of thistle rennet.
- Activity of wine against campylobacter jejuniPublication . Carneiro, Anabela; Couto, José António; Mena, Cristina; Queiroz, Jorge; Hogg, TimThis study focuses on the activity of wine against the important food-borne pathogen Campylobacter jejuni. The kinetics of inactivation of two strains of C. jejuni (one food-borne and one clinical) were characterised in various scenarios of exposure to wine and wine components. Undiluted wine was found to rapidly inactivate C. jejuni (>6D inactivation within 30 s); further inactivation data were obtained from experiments performed in wine diluted with water (1:2 and 1:4). Experiments with isolated antimicrobial fractions of wine (ethanol and certain organic acids) suggest that these two components act synergistically, demonstrating an inactivation capacity similar to wine itself. The results indicate that the exposure of contaminated food to wine, as in marinade conditions, Significantly reduces the number of viable cells of C. jejuni. A model stomach, containing a food matrix and a synthetic gastric fluid, was used to infer the effect of wine against C. jejuni in a consumption-like scenario. Wine was found to potentiate the anti-Campylobacter effect of gastric fluid. The results strongly suggest that the ingestion of wine during a meal may greatly diminish the quantity of C. jejuni persisting further in the alimentary tract, thus lowering the risk of infection
- Adoção de uma plataforma de e-learning nas instituições do ensino superior - modelo de processoPublication . Cardoso, Eduardo Luís; Pimenta, Pedro; Pereira, Duarte CostaAs tecnologias de informação e comunicação (TIC), entendidas como tecnologias educativas, são defendidas como podendo suportar de forma mais efectiva a construção de conhecimento no ensino superior. Os ambientes de aprendizagem (AA) baseados em plataformas de e-learning (PeL) e integrando aproximações construtivistas aos processos de ensino e aprendizagem são considerados particularmente adequados para o ensino superior. A proposta de trabalho de investigação consistiu num estudo de caso visando aprofundar a compreensão do fenómeno da adopção de PeL no suporte a AA nas IES. Foi definido como objectivo o desenvolvimento de um modelo de compreensão deste processo de adopção de tecnologias e sistemas de informação no suporte à prática lectiva, ao nível da pré-graduação. O modelo desenvolvido valoriza as influências e interacções entre o contexto institucional e as fases do processo de adopção de tecnologia e contempla a influência deste processo na evolução do próprio contexto institucional.
- Adsorption of fluorobenzene onto granular activated carbon: Isotherm and bioavailability studiesPublication . Carvalho, M.F.; Duque, A.F.; Gonçalves, I.C.; Castro, Paula M. L.The adsorption of a recalcitran fluoroaromatic compound, fluorobenzene (FB), onto granular activated carbon (GAC) was evaluated. The respective isotherm was obtained and the Langmuir, Freundlich and Redlich–Peterson models were fitted to the experimental data, with the Redlich–Peterson model giving the best fitting. Freundlich model also provided a good fit but the Langmuir model could not adequately fit the experimental data, especially at high FB concentrations. Maximal adsorption capacity of FB onto GAC was foundto be 388 mg of FB per gram of GAC. The reversibility of the adsorption of FB onto GAC was investigated, both in the absence and presence of microorganisms. Abiotic desorption of FB occurred to a small extent (between 3% and 22%, for amounts of FB initially adsorbed to the GAC between 37 and 388 mg g 1), and bioregeneration of GAC was shown to occur when the matrix was exposed to a FB degrading culture, with 58–80% of the adsorbed FB being biodegraded. A residual amount of FB showed not to be bioavailable, suggesting that part of the adsorbed FB may be irreversibly bound. The fraction of the non-bioavailable FB increased at higher amounts of adsorbed FB, from 19% to 33%. The results indicate that the GAC employed in this study has a good capacity to adsorb FB and that bioregeneration of this matrix is a feasible process.