Showing papers by "Raquel Guiné published in 2009"

Effcet of ripening stage on the solar drying kinetics and properties of S. Bartolomeu pears (Pirus Communis L.).

Abstract: Pears of the variety S. Bartolomeu ( Pyrus communis L.) have been used over the years in Portugal to produce a traditional dried pear known as “pera passa”. The processing comprehends a solar drying performed at open air, with obvious disadvantages, either concerning the drying efficiency or the sanitary quality of the final product, taking into account that the products are exposed to multiple contamination agents. For these reasons, attempts have been made to study alternative production methodologies, including the use of solar stoves, among others. In the present work pears of the variety S. Bartolomeu ( Pyrus communis L.), harvested at three different moments, corresponding to three ripening stages, were dried in a solar stove and their drying kinetics were studied, and the evolution of some properties was monitored along the drying process. From the results obtained it was possible to conclude that the equations used to model the drying kinetics fit with accuracy the experimental data, and that the climatic conditions that occurred in each drying period influenced the drying rate, being essay one clearly faster than the other two essays. On the other hand, considering the evolution of the properties of the pears along drying, it was possible to observe that the pears harvested in the two first dates showed quite similar trends through drying, while the pears harvested at the last date revealed a clear distinct behavior, allowing to deduce that the ripening stage at harvest plays an important role in the drying process.

Role and health benefits of different functional food components

Abstract: Functional food components are potentially beneficial components found naturally in foods or added to them as functional ingredients, and include carotenoids, dietary fiber, fatty acids, flavonoids, isothiocyanates, phenolic acids, plant stanols and sterols, polyols, prebiotics and probiotics, phytoestrogens, soy protein, vitamins and minerals. At present, professionals are recognizing that some functional components of foods have a major role in health enhancement. In fact, the big importance of these “bioactives” present in many foods, either naturally or added, has lead many scientists of different fields to conduct studies aimed for establishing the scientific basis that supports and validates the benefits of a particular food or component for the human health. It appears that people should strive to consume a wide variety of foods such as to assure the ingestion of compounds such as carotenoids, fiber, flavonoids, specific fatty acids, minerals, prebiotics and probiotics, phytoestrogens, soy protein and vitamins, among others, in order to reduce the risk of developing some diseases, or even to help curing others. In the present work, an examination of the characteristics of these compounds, the study and repercussions of these “bioactives molecules” allied to their ability to prevent and/or cure certain diseases will be object of study, based on recent evidence published in the medical journals.

Sorption Isotherms of Pears Using Different Models

Abstract: In the present work the desorption isotherms of 2 cultivars of pears produced in Portugal were determined for the temperatures of 20, 30 and 40°C. This range of temperatures was selected because it covers the range of average daily temperatures in Portugal in the summer, when the solar drying of pears takes place. The data were obtained using an orthogonal distance regression algorithm (ODR) to five different models found in literature, namely Chen, Guggenheim-Anderson-de Boer (GAB), Halsey, Henderson, and Oswin. From the present work, it was possible to conclude that the 2 cultivars of pears studied show a similar behavior, and that at constant moisture content an increase in temperature enhances water activity. By comparing the different models, it was possible to conclude that the Oswin model is less appropriate for describing the drying process, and that neither the Chen nor the Halsey model is adequate. The Henderson, and particularly, the GAB models were very good at describing the different situations.

Composition of Regional Portuguese Apple Cultivars in Different Harvest Years

Abstract: In the present study, apples of regional cultivars originating from Portugal were compared in terms of some chemical properties during three consecutive harvest years. It was possible to conclude that these regional cultivars of apples were generally sweeter and contained more minerals than other cultivars described in the literature. The data revealed that the acid, protein, and mineral content depended on the apple cultivar. The acid content varied notably with the 2004, 2005, and 2006 harvests. For total sugar or protein content, the variations observed were comparatively smaller. In the 2004 and 2005 harvests, the sugar and protein contents were similar but differ from the 2006 harvest. In respect to mineral content, the 2004 harvest registered the highest differences, and this was also the year when the apples had the highest maturation index, calculated as the sugar/acid ratio.

Influence of drying treatments on the colour of green bell peppers.

Abstract: The present work aims to evaluate the effect of different drying treatments on the colour of green bell peppers, which were dried using two different methods: air drying and freeze-drying. The treatments in air drying were carried out at 30 oC and 70 oC under an air flux of 300 m h. The colour of both fresh and dried samples were measured in L*a*b* colour space. The results obtained enable us to conclude that the air drying at 30 oC produces very small changes in colour whereas the air drying at 70 oC originates more intense colour changes. The values of L* increased, while values of a* and b* decreased during hot air drying. The colour change of freeze dried peppers was small, as compared with the vegetables dried at hot temperature. In order to preserve the colour, the most convenient drying method to drying the green pepper is the air drying at 30 oC, followed by the freeze drying treatment.