ESAV - DIA - Documentos de congressos (comunicações, posters, actas)
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Browsing ESAV - DIA - Documentos de congressos (comunicações, posters, actas) by Author "Almeida, Inês"
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- Biochemical and fungal characterization of dried pears and other fruitsPublication . Almeida, Inês; Guiné, Raquel; Costa, ElisaThe drying of pears allows their conservation due principally to the inhibition of microbial growth, making the dried pear a safe food for consumers. The knowledge of microbial flora, as well as some biochemical factors, is very important for ensuring the consumers health. In this study samples of pears of the variety S. Bartolomeu were dried under different systems: traditional open air sun drying, a solar stove, a solar drier and a drying tunnel. It was intended to isolate yeasts and moulds from dried pears subject to different drying processes, and also to some other fruits dried industrially. In this way, the following biochemical characteristics of dried fruits were evaluated: water activity and moisture content. Furthermore, the morphological characteristics of the isolates were also analyzed. Finally, as previously stated, the results obtained for dried pears were compared with the results obtained for samples of prunes and raisins, dried by industrial methods. The results of the biochemical characterization of the samples under study showed that all samples had a water activity lower than 0.60. After inoculated incubation it was only observed the grow of a mould in one sample of dried pears obtained by the traditional open air sun drying method, allowing to conclude that only this last method may induce the pears deterioration by microbial growth. The other systems tested for the drying of pears produce fruits that when dried can be conserved and consumed safely.
- Caracterização bioquímica e fúngica de peras e outros frutos secados.Publication . Almeida, Inês; Guiné, Raquel; Costa, ElisaA conservação de peras pela secagem ocorre principalmente devido à inibição do crescimento microbiano, tornando a pêra secada um alimento mais seguro para os consumidores (Guiné, 2008). O conhecimento da flora microbiana é de grande importância para se garantir a sanidade dos consumidores. O crescimento dos microrganismos pode ser prevenido devido à redução do conteúdo de humidade nas peras abaixo do nível crítico. Esse nível crítico é determinado por características particulares dos microrganismos e por características bioquímicas como a capacidade da água se ligar na pêra (actividade da água, aw), o que reduz a humidade livre (Pelczar, Chan e Krieg, 1996). Nos frutos secados os fungos só podem causar deterioração caso a aw seja relativamente elevada, pois não há crescimento microbiano para valores de aw entre 0,60 e 0,70 (Silliker, 1980). As peras secadas estudadas foram obtidas por diferentes processos de secagem: Tradicional, numa estufa solar na Escola Superior Agrária de Viseu (ESAV), num secador solar na Escola Superior de Tecnologia de Viseu (ESTV) e num túnel de secagem na Universidade de Coimbra (UC). Com este trabalho pretendeu-se isolar leveduras e fungos filamentosos a partir de amostras de pêra secada sujeitas aos diferentes processos de secagem. Neste sentido foram avaliadas as seguintes características bioquímicas da pêra secada: aw; humidade. Foi também realizada a avaliação de características morfológicas dos isolados obtidos. Para comparação dos resultados obtidos para as pêras secadas pelos diferentes métodos de secagem, foram também sujeitas a uma caracterização bioquímica e fúngica ameixas secadas e uvas-passa, secadas por métodos industriais. Relativamente às leveduras, os principais factores de caracterização baseiam-se no facto de crescerem à temperatura de 37º ou superiores, e transição dimórfica, por facilitar a adesão do fungo às células do hospedeiro. Em relação aos fungos a sua caracterização baseia-se na observação do micélio macroscopicamente e a observação de hifas com paredes transversais, ou não, microscopicamente.
- Comparative study of the drying kinetics of pears for different drying systems.Publication . Almeida, Inês; Guiné, Raquel; Lima, Maria João; Ferreira, DulcieniaOpen-air sun drying has been used since immemorial times to dry grains, vegetables, fruits and other agricultural products. This is a common method used to preserve foods and it is practiced until today in many countries where the combination of solar radiation, temperature and relative humidity is appropriate. However, despite being a cheap method, the open-air natural sun drying is not always applicable to large-scale production [1]. “Pera Passa de Viseu” denominates a traditional food product produced from pears of the variety S. Bartolomeu (Pyrus communis L.) using a traditional solar drying method, which is based on an open-air exposure [2]. Notwithstanding being quite a cheap drying method, making use of the sun as energy source, it has some very important disadvantages, like for example, the process is slow and very much dependent on weather conditions, and the quality of the product is not satisfactorily taking into account factors such as pollution from dust or from animal contamination or other types of infestation and microbial or mould contamination in humid environments. Therefore, the development of alternative drying methodologies assumes a pivotal role. The pears used in the present study were dried uncut after peeling, in three different systems: solar stove with forced convection, solar stove with natural convection and drying tunnel. The moisture content of the pulp was quantified along drying with a Halogen Moisture Analyzer. The objective of the present work is to fit the kinetic data to different models found in literature to describe the drying rates of food products, in order to compare the drying rates in the different systems tested and also to find out which model is best to describe the drying kinetics of these pears.
- Comparison of drying processes for the production of raisins from a seedless variety of grapesPublication . Almeida, Inês; Guiné, Raquel; Gonçalves, Fernando; Correia, Ana CristinaDrying is a very important preservation method that originates products with high nutritive value, among which the raisins, which are a very popular food product consumed worldwide. The objectives of the present work were to dry by different processes seedless grapes from variety Crimson, which is not traditionally used for the production of raisins. Furthermore, to compare the different methods tested, some analyses were made, namely at the chemical, physical and sensorial levels. The methodologies tested for the drying of the grapes were: direct exposure to the sun inside a solar stove and ventilated drying chambers with constant air flow at two different temperatures, 50 and 60 ºC. The technological parameter evaluated for the different dryings was the yield. At the chemical level were evaluated the moisture content, total sugars and acidity. In terms of physical properties were assessed the texture and colour, fundamental aspects for a good acceptation of dried products by the consumers. Lastly, a sensorial analysis was made to the dried products obtained, aimed at evaluating their acceptability by potential consumers. The raisins produced by the different methods didn´t show important differences either at the chemical or at the physical levels. Still, some aspects can be pointed out: the convective drying method allowed obtaining products with less moisture and in considerably less time, reaching 14.59 % in 47 hours for the drying at 60 ºC, while in the solar stove was obtained 19.43 % of humidity during 721 hours of drying. This result is very important from the economic point of view. Finally, at the sensory level, the tasters considers that the dried grapes produced in this work showed similar characteristics with some commercial raisins at sale in the Portuguese market.