Browsing by Author "Fontes, Luísa"
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- Assessing Serra da Estrela PDO cheeses’ origin-production date using fatty acids profilesPublication . Lima, M. J. Reis; Bahri, Hamdi; Morais, Jorge Sá; Veloso, Ana CA; Fontes, Luísa; Lemos, Edite Teixeira de; Peres, AntónioSerra da Estrela is a Portuguese traditional cheese produced with raw ewe’s milk from “Churra Mondegueira” and “Bordaleira” autochthonous breeds and the wild thistle flower (Cynara cardunculus L.), which benefits from the status of Protected Designation of Origin. Cheese chemical composition, namely the fatty acids profile, depends on milk composition and on manufacturing practices. Thus, the identification of possible chemical biomarkers capable of classifying Serra da Estrela cheeses according to the dairy manufacturing plant, geographical origin or production date would be of utmost relevance for producers and consumers. A typical fatty acids profile, including 23 saturated and unsaturated fatty acids, was identified for the studied cheeses, being butyric, caproic, caprilic, capric, lauric, miristic, palmitic, stearic, oleic, linoleic and its trans-isomer and α-linolenic acids the most abundant ones (relative mean abundances ranging from 1.4% ± 0.5% to 23.9% ± 1.9%). Linear discriminant models were established based on the most discriminative fatty acids (namely, caproic, caprilic, undecanoic, lauric, pentadecanoic, palmitic, palmitoleic, heptadecanoic, oleic, linoleic trans-isomer, heneicosanoic and arachidonic acids) that included less abundant fatty acids, which were selected using the simulated annealing algorithm. The established models enabled assessing cheeses’ origin (models based on 10–12 fatty acids) and/or production date (model based on 20 fatty acids) with predictive sensitivities of 71–88%. Therefore, fatty acids profiles coupled with chemometric techniques, could be foreseen as a fingerprint of cheese’s genuineness, enhancing the consumers’ confidence when purchasing this high-value cheese.
- Dataset on free amino acids contents of Serra da Estrela PDO cheeses determined by UPLC-DAD-MS/MSPublication . Lima, M. J. Reis; Santos, Andreia O.; Soraia, Falcão; Fontes, Luísa; Teixeira-Lemos, Edite; Vilas-Boas, Miguel; Veloso, Ana CA; Peres, AntónioThe composition of Serra da Estrela PDO cheeses (total fat, total protein, salt and free amino acids) was assessed using NIR spectrophotometry and UPLC-DAD-MS/MS. In total, 24 cheeses were acquired from 6 certified cheesemakers located in 5 different municipalities within the delimited PDO geographical region. Cheeses were produced from raw ewe milk of two autochthonous Portuguese sheep breeds, between November 2017 and March 2018, and were acquired after 45 days of maturation. The data include the mean (and respective standard deviations) levels of moisture (%), total fat (%), total protein (%) and salt (%), obtained by NIR spectrophotometry. As well the mean (and respective standard deviations) of free amino acids contents (mg/100 g of cheese, in wet basis) evaluated using a UPLC-DAD-MS/MS method are shown. The latter data include information regarding 8 essential free amino acids (histidine, leucine-isoleucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine) and 9 non-essential free amino acids (arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, proline, tyrosine and serine). Leucine and isoleucine, being isomers, were quantified together. Leucine-isoleucine, phenylalanine and serine were the most abundant essential free amino acids and cysteine, proline and asparagine were the most abundant non-essential free amino acids. Free amino acids contents depended on the cheese producer as well as on the production time-period.
- Drying kinetics and mass transfer properties in the drying of thistle flowerPublication . Guiné, Raquel; Fontes, Luísa; Lima, Maria JoãoThistle flowers, and particularly their stigmas, are used to coagulate milk in the production of a number of traditional Portuguese cheeses due to their high milk-clotting activity provided by the high content of aspartic proteases. The aim of the present work was to determine the mass transfer properties of thistle flower under different drying conditions: natural drying and convective drying. Convective drying took place in a convection chamber set at different temperatures (35 to 65 °C) and the process was terminated when the sample presented a moisture content of about 5% or less. The traditional drying method was also used, placing the thistle flowers in a dry place sheltered from the sun, and leaving them to dehydrate at the variable room temperature. The present work allowed for the conclusion that convective drying was much faster than natural drying, and that the drying rate increased with temperature. The drying curve revealed an initial constant rate period followed by a falling rate. All the five thin layer models tested to fit the experimental data were shown to adequately describe the drying of the thistle flowers, but the best one was the Page model. The drying constant increased with temperature as did the effective diffusivity and the mass transfer coefficient. The results allowed one to estimate the activation energy for moisture diffusion (57 kJ/mol) and for convective mass transfer (78 kJ/mol). Thus this study showed the possibilities for designing efficient drying processes for the thistle flower used for milk-clotting in the manufacture of traditional cheeses.
- Drying kinetics and mass transfer properties for the drying of thistle flowerPublication . Guiné, Raquel; Fontes, Luísa; Lima, Maria JoãoBecause the drying of tistle flower is important due to its utilization as curd coagulant in Serra da Estrela cheese production, this work intended to study the drying process of thistle flower, by comparing the convective drying at constant tepetrature with the natural drying with variable temperature. For that, the natural drying process was monitored as to the evolvution of water loss along time and different experiments were conducted for the convenctive drying with air at 0.5 m/s at different tenperatures (between 35 and 65 ºC). The kinetic data were fitted to different thin layer models from literature and also to the Fick’s second law of diffusion. Also the mass transfer correlations were used to compute the mass trnafer properties. The results obtained indicated that the different thin layer models tested fitted wel the experimental data, with values of R between 0.972 and 0.999, but with slightly best results if using the Modified Page model (loest value of R equal to 0.997). The values of the moisture diffusion and mass transfer coefficients in all cases were found to increase with increasing temperature of the drying air, from 35 to 65 ºC. The values of diffusivity increased from 1.902x10-10 to 1.300x10-9 m2/s and the values of the mass transfer coefficient increased from 5.731x10-9 to 8.049x10-8 m/s. The values of activation energy for moisture diffusion and for mass transfer were found to be 56.48 kJ/mol and 77.66 kJ/mol, respectively.
- Effect of the addition of different types of oenological commercial tannins on phenolic and sensorial red wine characteristics evolutionPublication . Jordão, António; Muxagata, Sara; Fontes, Luísa; Correia, Ana Cristina; Nunes, Fernando; Cosme, FernandaThe main objective of this work was to understand the effect of the addition of different commercial types of oenological tannins on red wine phenolic compounds and sensorial characteristics evolution. So, six different commercial oenological tannins obtained from different sources at an average dosage recommended by the manufactures were added to a red wine. During 120 wine aging days several phenolic parameters were analyzed (including several individual phenolic compounds by HPLC) and also the sensorial characteristics of the wines. Wines treated with oenological tannins showed higher total phenols and flavonoid phenols and lesser color degradation during the aging time considered. After 120 aging days, wines aged with oenological tannins showed After 120 aging days, wines aged with oenological tannins showed more total and individual anthocyanins and significantly more red color that induced significantly color differences in relation to the untreated wine (especially for the wines treated with condensed tannins). From a sensorial point of view it was also possible to detect a clear differentiation between the wines.
- Evaluation of colour in Serra da Estrela cheese produced in different dairies along maturation timePublication . Guiné, Raquel; Fontes, Luísa; Lima, Maria João“Serra da Estrela” cheese is a Portuguese traditional cheese with Protected Designation of Origin (PDO), and with a major importance in the national cheese making history. Due to its particular sensory characteristics, namely intense flavour, taste and aroma allied with a smooth texture, it is nowadays one of the most valued products both in Portugal and also abroad. The objective of this work was to compare the colour of Serra da Estrela Cheese manufactured in different dairies and to evaluate the changes that take place along the production season. The samples used for the study were obtained from 6 dairies situated in PDO region for this cheese. The colour measurements were made with a colorimeter in CIELAB coordinates: L*a*b*. To evaluate the colour change during milking season, the colour difference was also calculated. The results obtained in this work indicated that the colour characteristics of the Serra da Estrela Cheeses are slightly different between samples coming from different dairies where the cheeses are manufactured. Nevertheless, in the first moment of the evaluation period, the values of the colour coordinates varied in a limited range, which means that the variations could be considered acceptable attending to the nature of the traditional manufacture process associated with this PDO product. Furthermore, the results showed that along season very important changes in colour took place, which might be expected having in mind the nature of the physical-chemical changes produced in the pastures along time. However, these changes were found very much dependent of the dairy, as the results of total colour change demonstrated.
- Evaluation of drying kinetics and mass transfer in convective drying of Cynara cardunculusPublication . Guiné, Raquel; Fontes, Luísa; Lima, Maria JoãoThe dried thistle flower of C. cardunculus L., is widely used in the manufacture of various cheeses, in the Mediterranean regions and also in Portugal, where it is used for example to manufacture the traditional cheese owing the PDO (Protected designation of Origing) Serra da Estrela. In the present work the mass transfer properties of thistle flower (Cynara cardunculus, L.), were evaluated for the convective drying at temperatures between 35 and 65 ºC with and air flow of 0.5 m/s. The calculations followed two different algorithms, based on mathematical models derived from the thin layer drying equation and the Fick’s second law of diffusion. The results obtained indicated that the different methodologies resulted in different values of the mass transfer properties, which is an alert that care must be taken when choosing which calculation method might be more appropriate in a specific practical application. Regarding the values of the moisture diffusion and mass transfer coefficients, in all cases were found to increase with increasing operating temperature. The values of diffusivity increased from 2.7866x10-9 to 1.4027x10-8 m2/s when using the thin layer model based algorithm and from 1.9256x10-10 to 1.2033x10-9 m2/s, if based on the Fick’s equation model. The values of the mass transfer coefficient increased from 8.4335x10-8 to 8.4400x10-7 m/s and from 5.8277x10-9 to 7.2398x10-8 m/s, respectively for the thin layer or Fick’s law based models.
- Evaluation of texture in Serra da Estrela cheese manufactured in different dairiesPublication . Guiné, Raquel; Fontes, Luísa; Lima, Maria JoãoSerra da Estrela cheese is a traditional product from artisanal manufacture using raw ewe’s milk coagulated with dried, wild thistle flower. The present study aimed to investigate the variation of textural properties in Serra da Estrela cheeses manufactured in different dairies through time, namely from April to June, following the end of the cheese making season. Three types of tests were conducted: compression, puncture and spreadability. These were carried out on samples coming from six different dairies situated in the PDO (Protected Designation of Origin) region of this type of cheese. The results obtained showed some non-negligible differences for some textural properties between the top and bottom sides of the cheeses evaluated, as well as between cheeses from different dairies. Nevertheless, the properties of springiness, resilience, cohesiveness and adhesiveness (all from the compression test), were not significantly different in the samples analysed. In what concerns the variations along the milking season, it was possible to conclude that three of the considered dairies produced cheeses with a more constant textural profile in the period comprised between April and June. Furthermore, statistical analysis revealed that the correlations between the textural properties were strong for some interactions between properties form the same test and/or from similar nature.
- Evaluation of texture in Serra da Estrela cheese manufactured in different dairiesPublication . Guiné, Raquel; Fontes, Luísa; Lima, Maria JoãoSerra da Estrela cheese is a traditional product from artisanal manufacture using raw ewe’s milk coag- ulated with dried, wild thistle flower. The present study aimed to investigate the variation of textural properties in Serra da Estrela cheeses manufactured in different dairies through time, namely from April to June, following the end of the cheese making season. Three types of tests were conducted: compression, puncture and spreadability. These were carried out on samples coming from six differ- ent dairies situated in the PDO (Protected Designation of Origin) region of this type of cheese.The results obtained showed some non-negligible differ- ences for some textural properties between the top and bottom sides of the cheeses evaluated, as well as between cheeses from different dairies. Nevertheless, the proper- ties of springiness, resilience, cohesiveness and adhesive- ness (all from the compression test), were not significantly different in the samples analysed. In what concerns the variations along the milking season, it was possible to conclude that three of the considered dairies produced cheeses with a more constant textural profile in the period comprised between April and June. Furthermore, statis- tical analysis revealed that the correlations between the textural properties were strong for some interactions between properties form the same test and/or from similar nature.
- Fast and green method for the analysis of Serra da Estrela cheesePublication . Lima, Maria João; Fontes, Luísa; Guiné, RaquelSerra da Estrela (SE) cheese is a regional product making part of the gastronomic and sociocultural heritage of Portugal. It has several aspects that make it unique, namely the manufacturing by the coagulation of raw sheep milk using the thistle flower of Cynara cardunculus L., obtaining a final buttery texture with an exclusive typical flavour. The aroma compounds of Serra da Estrela cheese result partially from the action of indigenous microorganisms and enzymes on lactose, lipids and proteins. Although SE production is very ancient, there are few studies concerning its nutritional composition but nowadays consumers demonstrate interest in understanding the global composition of cheese, since it’s a product highly appreciated. In the last decades the use of near infrared spectroscopy (FT-NIR) has become comparable with those of the classical methods with representative advantages such as minimum laborious time sample preparation, it is a green technique (without using toxic reagents) and allows multiparametric determinations. To perform the present study, a total of 24 SE cheese samples were evaluated, originated from 6 representative producers and analysed with a FT-NIR Buchi NIRMaster™ standalone spectrometer with a spectral range of 800 – 2500 nm and compared with classical methods. SE cheese samples were evaluated in terms of salt, moisture, protein and fat content. In all the studied samples the moisture varied between 42 % and 53 %, the fat content between 19.6 and 33.3 %, the protein content between 18.6 and 26.7 % and the salt between 0.7 and 2.2 %. The results showed a significant agreement between the pairs of values obtained for the studied parameters.