Showing papers by "Raquel Guiné published in 2010"

Analysis of the drying kinetics of S. Bartolomeu pears for different drying systems.

Abstract: Pears of the variety S. Bartolomeu (Pyrus communis L.) are used in Portugal to produce a traditional food product, obtained by open-air sun drying. The traditional processing has many disadvantages, namely the efficiency and the sanitary quality of the final product. For these reasons, attempts were made to study alternative production methodologies, including the use of a solar stove, a solar drier and a drying tunnel. In this work pears of the variety S. Bartolomeu, were dried in the three alternative systems mentioned, and their drying kinetics was studied. Eight different models from literature were tested and their performance was evaluated in terms of some statistical indicators. The results allowed concluding that the models Henderson & Pabis, Logarithmic and Vega-Lemus were the best to fit the experimental data. Furthermore, it was concluded that the solar drying was very dependent on the weather conditions. It was also possible to observe that the loss of water was much more uniform in the drying tunnel system when compared to the solar dryings, because in the tunnel the operating temperature and air velocity were constant.

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.

Food, Diet and Health. Past, Present and Future Tendencies.

Abstract: Preface Public health nutrition's time has come Social Impact of modern diet and tendencies Functional components of foods Food products that help to promote human health Aspects of legislation regarding foods with a functional ability Future trends involving food processing technology Challenges regarding enriched or target specific foods Food enrichment: bioavailability of nutrients and effects The future of human nutrition Index.

Consumer study and sensorial evaluation of a newly developed spicy strawberry syrup

Abstract: The potential beneficial effects of strawberry allied to those of chilly in many aspects of human health lead to the development of a spicy strawberry syrup. The work included the development of the product, including formulation, processing and industrialization aspects, chemical and sensorial analyses as well as a consumer study, of which some will be analysed in the present manuscript. The sensorial evaluation was performed with a panel of 25 tasters, of which 17 were women and 8 men. The parameters evaluated using a hedonic scale were: visual aspect, colour, consistence, brightness, sweetness, strawberry taste, spicy taste, global appreciation. To characterization of the product a brief chemical analysis was made. The mineral content was determined by calcination at 550 oC, the total soluble solids (mainly sugars) were determined by refractometry and the moisture by a halogen moisture analyser. In all characteristics evaluated in the sensorial analysis the medium punctuation was 4 (in a scale from 0 to 5), corresponding to Good. Despite the product being considered quite spicy, its acceptance was very good.

Phenolic, dietetic fibre and sensorial analyses of apples from regional varieties produced in conventional and biological mode

Abstract: In the present work apples from eleven regional varieties originating from Portugal were studied in terms of their content in phenolic compounds and dietetic fibres (soluble and insoluble). In some cases, apples from two different production modes were analysed: conventional and biological. Some of the most commercialized apples in Portugal were also studied for comparison purposes. In addition, a sensorial evaluation of some of the varieties was performed. From the present work it was possible to conclude that the regional varieties studied contain higher amounts of dietetic fibre than those of commercial varieties and other fruits. With respect to the content in total phenolic compounds, the apples of regional varieties showed values clearly higher than those quantified in commercial varieties, and being concentrated mainly on the peel, then on the seeds, and finally on the pulp. From the sensorial analyses was possible to infer that the regional varieties which were more appreciated were Bravo de Esmolfe and Camoesa de Alcongosta.

Analysis of the alterations in the color of pears dried under different systems.

Abstract: In Portugal, pears are traditionally dried by a direct sun-exposure method. However, because of the disadvantages associated with this procedure, alternative dryings are being tested. The objectives of this study were to evaluate how drying influences the color of pears, and to compare the products dried through different systems, to evaluate which one allows obtaining a product as much as possible with the same color of the traditional pears. From the results obtained it was possible to verify that drying in systems with exposure to the sun (through glass) allow obtaining products that do not differ much from the traditional dried pears.

Texture of onions before and after freeze-drying.

Abstract: In the present work the textural properties of onion, fresh and after freeze-drying, were studied, to understand how this drying treatment influences the texture of this food product. The fresh product had an average moisture content of 90.02 % and the freeze-dried onion had a moisture content of 5.19 %. From the TPA to the fresh samples and to the freeze-dried samples it was possible to conclude that the hardness of the onions decreased very much from the fresh to the dried state. A similar behaviour was observed for the chewiness, which also decreased, but in a much less extent. On the other hand, cohesiveness increased slightly with drying. In relation to springiness, this property was not affected from drying, being the value in the fresh state quite similar to the value in the freeze-dried state.

Properties of regional portuguese apple cultivars produced in conventional and organic modes.

Abstract: The present study involved examining the physical and chemical attributes of seven regional Portuguese apple cultivars. The apples analyzed were produced in two different production modes: conventional and biological, to verify in the extent to which these variables influenced the results. The data obtained enabled us to conclude that the chemical properties: moisture content, total and reducing sugars, protein, and ash, were influenced by the production mode in different ways, depending on the cultivar. As to the textural properties estimated, the results showed that the cultivar ‘Lila’ was the one that presented the greatest similarity when comparing the conventional with the biological modes of production. Furthermore, it was possible to observe that the production mode did not significantly influence the fiber content in the cultivars of apples analyzed.

Variation along drying of the textural properties of pears.

Abstract: M. J. Barroca, R. P. F. Guine, M. J. Lima, D. M. S. Ferreira CERNAS, Polytechnic Institute of Coimbra, ISEC, DEQB, Rua Pedro Nunes, Quinta da Nora, 3030-199 Coimbra, Portugal; e-mail: mjbarroca@gmail.com; CID e-mail: raquelguine@esav.ipv.pt;; CID e-mail: mjoaolima@esav.ipv.pt; CID e-mail: ferdulcineia@esav.ipv.pt.

Análise SWOT à produção da pêra passa de Viseu

Abstract: O presente trabalho consistiu na realizacao de inqueritos, junto dos operadores da pera de Sao Bartolomeu e respectivo fruto secado, que sao a Cooperativa Agricola de Fruticultores da Beira Alta CRL e a Cooperativa Agricola de Mangualde CRL, no sentido de conhecer as caracteristicas de producao e comercializacao deste produto regional. Foi ainda realizada uma analise SWOT, ou seja, uma analise dos pontos fortes, pontos fracos, oportunidades e ameacas, com vista ao estabelecimento de um plano de accao.

Effects of drying on pumpkin and green peper colour.

Abstract: The present work evaluates the effect of different drying treatments on the colour of green bell peppers and pumpkin, 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. Overall, it was possible to conclude that air drying at 30 oC produces small changes in colour of green pepper whereas air drying at 70 oC and freeze drying originate more intense colour changes. The increase of temperature on air drying augments the colour saturation of dried pumpkin while decreases the hue angle by a linear relationship. In addition, the chroma of dried pumpkin decreases significantly with the freeze drying, while the hue angle is maintained constant as compared with the fresh vegetable.

Empirical models to describe the solar drying of S. Bartolomeu pears.

Abstract: In Portugal, pears of the variety S. Bartolomeu (Pyrus communis L.) have been used to produce a traditional product named “pera passa de Viseu”. These pears are dried at direct open air sun exposure, following a multi-step procedure. In the last years some investigation around this product and the production method has been carried out to better understand them and establish alternative production techniques. In the present work some study was carried out in order to find empirical models capable of describing the variation of relative weight loss along the solar drying of pears with some air properties (temperature and relative humidity) and also with some material properties (moisture content and total soluble solids content). Two kinds of software were used to estimate the parameters of the tested models, SigmaPlot and ODRPACK, and the results enabled us to conclude that the fittings obtained with both were consistent.

Avaliação físico-química e sensorial da pêra passa de Viseu secada por diferentes metodologias.

Abstract: Resumo A pera de S. Bartolomeu (Pyrus communis L.) e um produto tradicional da regiao de Viseu comercialmente designada de “Pera Passa de Viseu” e que, presentemente, e secado ao ar livre. De modo a substituir esse processo de secagem artesanal sem alterar as caracteristicas tipicas do produto ao nivel organoleptico, foram testadas metodologias alternativas, designadamente, estufa solar de conveccao forcada, realizada na Escola Superior Agraria de Viseu (ESAV); estufa solar de conveccao natural, na Escola Superior de Tecnologia de Viseu (ESTV) e secador em tunel, na Universidade de Coimbra (UC). Os produtos secados pelas varias metodologias foram analisados ao nivel fisico-quimico e sensorial nos seguintes parâmetros: cor, textura (dureza e elasticidade), acidez e acucares totais. Os resultados obtidos foram submetidos a uma analise estatistica multivariada em componentes principais (SPSS, versao 18), tendo as 2 componentes principais explicado 73% da variacao total. O eixo 1 e descrito essencialmente pela variavel da cor e o eixo 2 pela dureza. Na projeccao das metodologias no plano definido pelas duas componentes principais verificou-se que o produto secado em tunel apresentava caracteristicas diferentes das restantes metodologias de secagem, principalmente por apresentar uma cor mais amarelada e nao o vermelho-castanho tradicional da pera passa de Viseu. No que respeita a dureza, as peras secadas pela estufa solar de conveccao natural apresentavam uma dureza menor. Este trabalho permitiu concluir que e possivel substituir a secagem tradicional da pera passa de Viseu por outras metodologias. A estufa solar de conveccao forcada foi a que apresentou melhores resultados.

Modelling of the thin layer drying kinetics of pears.

Abstract: R. P. F. Guine, M. J. Barroca, M. J. Lima, D. M. S. Ferreira CID tel. + 351 232 446 641, e-mail: raquelguine@esav.ipv.pt; CERNAS, IPC, ISEC, DEQB, Rua Pedro Nunes, Quinta da Nora, 3030-199 Coimbra, Portugal; e-mail: mjbarroca@gmail.com; CID e-mail: mjoaolima@esav.ipv.pt; CID e-mail: ferdulcineia@esav.ipv.pt.

Comparative study of pear drying using solar stove and tunnel drying

Abstract: Sun-dried pears of Portuguese variety S. Bartolomeu are relatively small fruits with peculiar organolephtic characteristics. The open sun drying has some disadvantages related with drying efficiency and food safety. However the drying with an economic and friendly energy source is an important characteristic of the drying methods and therefore several attempts have been made to develop processes using solar drying. The present work studies two drying methods, namely solar stove and tunnel drying, with the advantages of using the solar energy and simultaneously reducing the exposure of fruits to contamination agents. Both processes were conducted in two consecutive years to analyse if the behaviour of each drying method shows evidence of a similar pattern. The results enable us to conclude that the variation of normalized moisture of pears with the drying time follows a linear relationship in the solar stove while an exponential decay is observed in the tunnel drying. Despite the different climatic conditions, it is possible still to observe that the behavior of each process is quite similar in both consecutive years. However, in the second year the drying tends to be faster in both processes. In addition, it is also possible to conclude that the total soluble solids/acidity ratio has a similar behavior along the drying in the two years for each process. However, the decrease in acidity of pears in the solar stove is more pronounced than the total soluble solids (TSS) and consequently a higher ratio of TSS/acidity is observed along the solar stove drying when compared with the tunnel drying.

Properties of pears dried with different drying processes.

Abstract: Pears of S. Bartolomeu variety have been used over the years in Portugal to produce a traditional dried pear using the cheapest practice with environmental friendly characteristics: open-sun drying. However, the obvious disadvantages concerning the drying efficiency and safety of the dried product have been an incentive to design or improve solar drying methods as an alternative to the traditional one. The present work has tested three types of drying processes, namely solar stove, solar drying and tunnel drying. In addition, the efficiency of drying and the properties of the dried pears were compared with the traditional dried fruits. The results of the tests have allowed us to conclude that all methods have lead to a considerable reduction in drying time as compared to open-sun drying. Indeed, the drying time for the solar stove and the solar dryer showed a reduction of 40% while in the drying tunnel this reduction increased to 60%. In addition, it was also possible to conclude that the properties of the dried pears obtained by the three processes correspond to a dried fruit similar to the traditional dried pears. Thus, based on these results, it can be inferred that the traditional sun drying at open-air can be replaced by either of the processes tested in the present study, which, allow a higher drying efficiency associated to a higher safety of the dried food, while maintains the properties of the traditional food product.