Browsing by Author "Morais, Alcina M.M.B."
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- Avaliação do "shrinkage" ao longo da secagem por convecção de castanha (Castanea sativa)Publication . Ramalhosa, Elsa; Lamas, Hugo; Pereira, J.A.; Morais, Alcina M.M.B.No presente trabalho pretendeu-se avaliar o efeito da secagem por convecção a várias temperaturas nas dimensões de castanhas (Castanea sativa) da variedadc "Longal", de forma a determinar se o "shrinkage" é significativo ou não ao longo da secagem e, dessa forma, inferir da adequabilidade de se usar algumas equações na modelagem matemática da secagem deste fruto, nas quais se assume que na dimensão se mantém constante.
- Avaliação do "shrinkage" ao longo da secagem por convecção de castanha (Castanea sativa)Publication . Ramalhosa, Elsa; Lamas, Hugo; Pereira, J.A.; Morais, Alcina M.M.B.Geralmente nos estudos que envolvem modelagem matemática da secagem por convecção de castanha (Castanea sativa), os frutos são aproximados a corpos esféricos e assume-se que a dimensão dos mesmos se mantém constante ao longo da secagem. Neste trabalho pretendeu-se encontrar um modelo que relacionasse, de forma simples e rápida, as dimensões axiais das castanhas com o diâmetro de esferas de volume equivalente e avaliar se o efeito de “shrinkage” era significativo ou não ao longo da secagem por convecção a diferentes temperaturas. Para tal, determinaram-se as dimensões axiais (a, b, c) e calcularam-se os diâmetros médios aritmético (Da) e geométrico (Dg), a esfericidade e os diâmetros das esferas equivalentes a castanhas da variedade “Longal”, utilizadas no presente trabalho. Procedeu-se posteriormente à sua secagem por convecção a diferentes temperaturas, designadamente a 40, 50, 65, 85 e 100ºC e avaliou-se o seu efeito nas dimensões dos frutos. Verificou-se que os Da e Dg permitiram estimar os diâmetros das esferas equivalentes, x, através de dois modelos lineares: y=0,771x+0,730, r = 0,922 e y=0,814x+0,545, r = 0,916, respectivamente. Além disso, verificou-se que um modelo do tipo: diâmetro estimado pelo modelo = k1a + k2b + k3c + k4ab + k5bc + k6ac + k7(abc)n, também permitiu relacionar de forma adequada estes diâmetros estimados com os das esferas correspondentes (r = 0,949) demonstrando que as castanhas podem ser consideradas corpos esféricos com diâmetros estimados a partir das dimensões axiais, as quais são fácil e rapidamente determinadas. Em relação à secagem por convecção a diferentes temperaturas, verificou-se um comportamento linear (r entre 0,834 e 0,997) entre as três dimensões axiais das castanhas com casca, avaliadas no início e no final de cada experiência, determinando-se na maior parte dos casos declives próximos de 1,0. Estes resultados indicam que as castanhas com a casca não sofrem um efeito de “shrinkage” significativo ao longo da secagem. Após calcular a proporção do fruto interno sem casca em relação ao fruto com casca ao longo das secagens a diferentes temperaturas, verificou-se que a mesma variou entre 78,3+4,3 e 89,2+4,6 % e que, para cada temperatura, se observou uma diminuição nessa percentagem ao longo do tempo, indicando que o fruto internamente sofreu efeito de “shrinkage” significativo à medida que foi secando. Em conclusão, este trabalho permitiu verificar que no futuro ao realizar a modelagem da secagem por convecção da castanha pode aproximar-se a mesma a esferas com diâmetros estimados a partir de Da, Dg ou de outro modelo que seja adequado. No entanto, deve-se ter em conta a forma como a castanha se encontra, designadamente com ou sem casca, uma vez que o efeito de “shrinkage” poderá ser significativo na castanha sem casca.
- Equipment's role on the drying process of chestnut (Castanea sativa Mill.) fruitsPublication . Lamas, Hugo; Ramalhosa, Elsa; Morais, Alcina M.M.B.In the present work, drying of chestnut (Castanea sativa Mill.) fruits was performed at different air temperatures in three equipments - convection oven, parallel flow tray dryer and fluidised bed dryer, at temperatures between 40 and 100°C. Newton diffusion approach and two-term models were found to be adequate in describing the moisture ratio and drying rates along time. For the same temperature, the dehydration processes that involved higher air velocities were > 1.6 times faster. On the other hand, for the same equipment the highest temperature (100°C) induced a drying rate ten times faster than the lowest temperature (40°C), reducing drying time. Apparent diffusivity ranged between 7.03 × 10^-11 m2 s-1 (40°C, convection oven) and 1.06 × 10^-9 m2 s-1 (100°C, fluidised bed dryer). In convection oven experiments, the diffusivity in function of temperature was well described by an Arrhenius type function, with an activation energy of 4.08 × 10^4 J mol-1.
- Functional Dehydrated Foods for Health PreservationPublication . Morais, Rui Manuel Santos Costa; Morais, Alcina M.M.B.; Dammak, Ilyes; Bonilla, Jeannine; Sobral, Paulo José A.; Laguerre, Jean Claude; Afonso, Maria João A.P.S.; Ramalhosa, Elsain a healthy lifestyle. Dried fruits constitute good snacks, in alternative to salty or sweet ones, and food ingredients due to their taste and nutritional/health benefits. Bioactive molecules are interesting sources to develop functional foods, as they play a major role in improving the health status and minimizing disease risks. The bioactive compounds most widely discussed in literature are presented in this review, for example, polyphenols, phytosterols, and prebiotics. Different technologies to dry bioproducts for producing functional foods or ingredients are presented. New drying techniques for the preservation of bioactive compounds are proposed, focusing more specifically on dielectric drying. A discussion on the techniques that can be used to optimize drying processes is performed. An overview on dehydrated plant based foods with probiotics is provided. The microorganisms used, impregnation procedures, drying methods, and evaluated parameters are presented and discussed. The principal bioactive compounds responsible for nutritional and health benefits of plant derived dried food products—fruits and vegetables, fruits and vegetables by-products, grains, nuts, and algae—are presented. Phytochemical losses occurring during pretreatments and/or drying processes are also discussed.
- Impact of postharvest preservation methods on nutritional value and bioactive properties of mushroomsPublication . Marçal, Sara; Sousa, Ana Sofia; Taofiq, Oludemi; Antunes, Filipa; Morais, Alcina M.M.B.; Freitas, Ana Cristina; Barros, Lillian; Ferreira, Isabel C.F.R.; Pintado, ManuelaBackground: Mushrooms are a good source of protein, dietary fibre, vitamins, minerals and phenolic compounds. However, mushrooms are a very perishable food and the implementation of preservation methods is essential to extend their shelf-life. The preservation methods for mushrooms can be classified into three categories: thermal (drying/freezing), chemical (edible coatings, films and washing solutions) and physical (packing, irradiation, pulsed electric field and ultrasound) processes. These processes can change the nutritional value and bioactive properties of this commodity. Scope and approach: The goal of this review is to critically update and discuss the existing information about the effect of postharvest preservation methods on the nutritional value and bioactive properties of edible mushrooms. Key findings and conclusions: Drying, especially when high temperatures are applied, can cause the degradation of polysaccharides, proteins and flavour compounds. Freezing is one of the best methods to extend mushrooms’ shelf life but cause the loss of vitamins. Edible coatings and films improve the total sugar, ascorbic acid and bioactive compounds preservation during the storage period. Washing solutions decrease amino acids content. Gamma and electron-beam irradiation decrease the unsaturated fatty acid content, whereas UV-B irradiation significantly increases the vitamin D content. However, there is still limited information about the impact of chemical processes, packaging, pulsed electric field and ultrasound on the nutritional composition and bioactive properties of mushrooms, opening research opportunities for future. This review presents technological and economic alternatives that may support the mushroom processing industries to obtain value-added edible mushrooms and related products.
- Physical characteristics and drying kinetics of Portuguese "Longal" chestnutPublication . Ramalhosa, Elsa; Lamas, Hugo; Pereira, J.A.; Morais, Alcina M.M.B.Chestnut is a fruit of great importance in Portugal, being generally sold fresh or frozen. Alternative products may be obtained by hot air drying. The present work is on the dehydration behavior of Portuguese ‘Longal’ chestnut, that is the most used in industry. Different models for representing the variations of water content and drying rate along time were tested successfully. As expected, higher temperatures correspond to faster drying processes. The apparent diffusivity was predicted by Fick’s second law equation, and it ranged from 1.25x10-11 m2/s, at 20ºC, to 8.42x10-10 m2/s, at 100ºC.