Browsing by Author "Dias, L.G."
Now showing 1 - 10 of 221
Results Per Page
Sort Options
- Alterações dos parâmetros físico-químicos e sensoriais de azeite virgem extra durante o uso doméstico simulado ao longo de um mêsPublication . Rodrigues, Nuno; Oliveira, Letícia; Mendanha, Lorena; Sebti, Mohamed; Dias, L.G.; Oueslati, Souheib; Veloso, Ana C.A.; Pereira, J.A.; Peres, António M.O azeite tem características sensoriais e nutricionais únicas, o que torna altamente apreciado pelos consumidores. Neste trabalho estudaram-se as alterações da qualidade do azeite que podem ocorrer ao longo de um mês de consumo doméstico simulado.
- Alterações dos parâmetros físico-químicos e sensoriais de azeite virgem extra durante o uso doméstico simulado ao longo de um mêsPublication . Rodrigues, Nuno; Oliveira, Letícia; Mendanha, Lorena; Sebti, Mohamed; Dias, L.G.; Oueslati, Souheib; Veloso, Ana C.A.; Pereira, J.A.; Peres, António M.O azeite tem características sensoriais e nutricionais únicas, o que o torna altamente apreciado pelos consumidores
- Amino acids profile for assessing Serra da Estrela cheese producersPublication . Santos, Andreia O.; Falcão, Soraia; Fontes, Luísa; Veloso, Ana C.A.; Lemos, Edite Teixeira de; Lima, M.J. Reis; Peres, António M.; Dias, L.G.This work has the purpose to evaluate if the Serra da Estrela cheeses colletcted from 6 producers have typical chemical characteristics, with controlled variability, considering that cheeses were produced during time periods, the raw milk comes from different animals, and that the cheese processing may slightly differ between cheesemaking producers.
- Amino acids profile for assessing Serra da Estrela cheese producersPublication . Santos, Andreia O.; Falcão, Soraia; Fontes, Luísa; Veloso, Ana C.A.; Lemos, Edite Teixeira de; Lima, M.J. Reis; Peres, António M.; Dias, L.G.This work has the purpose to evaluate if the Serra da Estrela cheeses colletcted from 6 producers have typical chemical characteristics, with controlled variability, considering that cheeses were produced during time periods, the raw milk comes from different animals, and that the cheese processing may slightly differ between cheesemaking producers.
- An electronic tongue for beer differentiationPublication . Dias, L.G.; Peres, António M.; Barcelos, Tânia P.; Morais, Jorge Sá; Machado, Adélio A.S.C.In this work an electronic tongue, based on a potentiometric solid-state mufti-sensor array, with 36 polymeric membranes, was built for developing an analytical tool to apply in process monitoring and quality control. As a first approach, this tool was applied together with a supervised pattern recognition tool to semi-quantitatively differentiate beers with different alcoholic levels.
- An electronic tongue for gliadins semi-quantitative detection in foodstuffsPublication . Peres, António M.; Dias, L.G.; Veloso, Ana C.A.; Meirinho, Sofia G.; Morais, Jorge Sá; Machado, Adélio A.S.C.An all-solid-state potentiometric electronic tongue with 36 polymeric membranes has been used for the first time to detect gliadins, which are primarily responsible for gluten intolerance in people suffering from celiac disease. A linear discriminant model, based on the signals of 11 polymeric membranes, selected from the 36 above using a stepwise procedure, was used to semi-quantitatively classify samples of a “Gluten-free” foodstuff (baby milked flour), previously contaminated with known amounts of gliadins (<10, 20–50 or >50 mg/kg), as “Gluten-free”, “Low-Gluten content” or “Gluten-containing”. For this food matrix, the device had sensitivity towards gliadins of 1–2 mg/kg and overall sensitivity and specificity of 77% and 78%, respectively. Moreover, the device never identified an ethanolic extract containing gliadins as “Gluten-free”. Finally, the system also allowed distinguishing “Gluten-free” and “Gluten-containing” foodstuffs (15 foods, including breads, flours, baby milked flours, cookies and breakfast cereals) with an overall sensitivity and specificity greater than 83%, using the signals of only 4 selected polymeric membranes (selected using a stepwise procedure). Since only one “Gluten-containing” foodstuff was misclassified as “Gluten-free”, the device could be used as a preliminary tool for quality control of foods for celiac patients.
- An electronic tongue for juice level evaluation in non-alcoholic beveragesPublication . Peres, António M.; Dias, L.G.; Barcelos, Tânia P.; Morais, Jorge Sá; Machado, Adélio A.S.C.An electronic tongue with 36 cross-sensibility polymeric membranes was built and applied for qualitative beverage analysis.
- An electronic tongue for juice level evaluation in non-alcoholic beveragesPublication . Peres, António M.; Dias, L.G.; Barcelos, Tânia P.; Morais, Jorge Sá; Machado, Adélio A.S.C.An electronic tongue with 36 cross-sensibility polymeric membranes was built and used for semi-quantitative analysis of beverages. The objective was to differentiate 4 non-alcoholic beverage groups with different added fruit juice contents: higher than 30%, between 14%-30%, 5%-10% and 0.1%-2%. A set of 16 Portuguese beverages (4 for each group), purchased in commercial supermarkets, was analyzed and the respective signal profiles recorded by the electronic tongue device. The data obtained were treated by stepwise linear discriminant analysis, allowing a 100% overall correct classification for the original grouped cases and a 93.8% for the “leaving one-out” cross-validation procedure
- Analysis of acids and sugars in fruit-based drinks by SEC-UV-RIPublication . Sequeira, Cédric Basílio; Dias, L.G.; Morais, Jorge Sá; Veloso, Ana C.A.; Machado, Adélio A.M.; Peres, António M.Beverage industry produces a large and diverse range of soft drinks, beverages containing flavourings and/or fruit juices (sodas and fruit juices), of which t he quality and safety must be monitored to protect and satisfy customers. From the raw ingredients to the final product, quality control is needed to ensure product safety, quality, labelling, regulatory compliance and consistency. The development of analytical techniques for simultaneous analysis of different compounds essential to control the product quality, as an alternative to several independent traditional reference methods, is of major importance. Therefore, the present work reports the application of size exclusion chromatography (SEC), which allows carrying out analysis free of organic solvents, using two detectors coupled in series - Ultraviolet (UV) and Refractive Index (RI) - for the simultaneous analysis of acidifiers (citric, tartaric, lactic, acetic, malic and ascorbic acids, by UV), and sweeteners (sucrose, glucose and fructose by RI), in commercial non-alcoholic beverages with different levels of added fruit juice. Ascorbic acid is used as a stabilizer in the soft drinks, improving the beverage shelf-life stability due to its antioxidant properties. The results showed that the simultaneous calibrations for acid compounds (UV) and for glucose (RI) were straight-forward. On the other hand, for sucrose and fructose simultaneous analysis, the calibrations (RI) were more complex since the predictive models established had to take into account malic and tartaric acids interferences, regardless the good resolution between the peaks of sucrose and fructose. Finally, the results for sample analysis showed that all the sugars evaluated were present in the juice drinks as well as the citric, tartaric, malic and ascorbic acids. In all samples, lactic and acetic acids were not detected.
- Analysis of honey main sugars by size-exclusion chromatographyPublication . Sousa, Mara E.B.C.; Peres, António M.; Dias, L.G.; Morais, Jorge Sá; Estevinho, Leticia M.; Machado, Adélio A.M.The main constituents of honey are sugars, mainly the monosaccharides fructose and glucose (reducing sugars), which account for 80% of the total mass, while the disaccharides (especially sucrose and maltose) represent 10%. In general, fructose predominates (giving a sweeter taste to honey than sucrose), although, in some honeys, glucose (that assigns a less sweet taste than sucrose but more than maltose) may be the main sugar. The fructose/glucose mass ratio is a parameter that allows the identification of possible adulterations of honey, by signaling abnormal levels of glucose due to the addition of commercial glucose or syrups. It also allows assessing the crystallization trend of the honey, although the glucose/water ratio provides a more accurate indication of this behavior. Therefore, for marketing purposes, the quantification of glucose and fructose in honey is a key factor for establishing its quality. This work reports the validation of a method for determination of honey sugars by SEC to be used as control in the study of their determination with an electronic tongue. A set of honey samples was provided by the Portuguese National Federation of Beekeepers to obtain a national sampling which showed the natural composition variability of Portuguese honeys. The analysis were carried out with HPLC equipment from Varian and a Supelcogel C-610H column, selected because the elution does not require organic solvents. The target compounds to analyze were glucose and fructose for which well separated peaks were found in the chromatograms, which included other two, for a mix of polyssacharides and unknown substance(s). The results of a thorough validation showed that the method can be employed for quantification of these two sugars in honey samples.