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Influência das cascas e películas na cinética de secagem de castanhas (Castanea sativa Mill.)

Publication . Delgado, Teresa; Pereira, J.A.; Baptista, Paula; Casal, Susana; Ramalhosa, Elsa

O objetivo do presente trabalho foi analisar se existiam diferenças na cinética de secagem de castanhas (Castanea sativa Mill.) secas a 50 °C, com e sem casca exterior. Neste estudo foram estudadas duas variedades portuguesas, Longal e Judia. A adequação de dois modelos matemáticos de secagem, Page e Two-term, foi analisada. Adicionalmente, pela primeira vez, foram realizadas análises microscópicas à casca exterior e película, a fim de detetar diferenças entre as duas variedades. Verificou-se que o comportamento de secagem de ambas as variedades com casca e com película foram semelhantes. Além disso, pequenas diferenças no tempo de secagem foram obtidas quando se removeu a casca exterior da castanha, verificando-se que esta deve ter uma pequena influência na perda de água. Bons ajustes entre os dados experimentais e os previstos pelos dois modelos matemáticos estudados foram obtidos. Contudo, pequenas diferenças foram detetadas nas cascas exteriores das duas variedades de castanha, tendo apresentado a Judia uma maior espessura do que a Longal. No entanto, em relação ao formato das células, na variedade Longal estas são mais regulares do que na variedade Judia.

2014Conference paper

Open access

Comparison of different drying methods on the chemical and sensory properties of chestnut (Castanea sativa M.) slices

Publication . Delgado, Teresa; Pereira, J.A.; Ramalhosa, Elsa; Casal, Susana

The aim of this work was to determine the effect of hot-air convective drying (D), osmotic dehydration (OD), osmotic dehydration + drying (OD + D) and freeze-drying (FD) on chemical and sensorial characteristics of chestnut slices. Proximate composition, sugars, organic acids and lipid profiles were determined along 60 days of storage. Immediately after production, D and FD samples had similar proximate compositions, both with higher fat and protein contents than the osmodehydrated ones, the latter with increased sucrose contents. FD was the method that better preserved starch, amylose, ascorbic and citric acid molecules at day 0, while D originated samples with higher glucose and fructose contents. Along storage, the major variations were observed on organic acids: ascorbic acid decreased on all methods, while fumaric acid increased. Only small variations were observed on the fatty acids and vitamin E profiles and amounts. All samples presented similar and good overall sensorial acceptance with the exception of D. FD was the method that better preserved the sensorial characteristics until 60 days of storage, while D only preserved freshness until 15 days and OD + D until 30 days. In general terms, the most adequate and accepted preservation methods to apply to chestnuts would be FD and OD + D.

2017Journal article

Open access

Optimization of osmotic dehydration of chestnut (Castanea sativa Mill.) slices using response surface methodology

Publication . Delgado, Teresa; Paim, Bruna; Pereira, J.A.; Casal, Susana; Ramalhosa, Elsa

Osmotic dehydration of chestnut slices in sucrose was optimized for the first time by Response Surface Methodology (RSM). Experiments were planned according to a three-factor central composite design (α=1.68), studying the in uence of sucrose concentration, temperature and time, on the following parameters: volume ratio, water activity, color variation, weight reduction, solids gain, water loss and normalized moisture content, as well as total moisture, ash and fat contents. The experimental data was adequately fitted into second-order polynomial models with coeffcients of determination (R2) from 0.716 to 0.976, adjusted-R2values from 0.460 to 0.954, and non-significant lacks of fit. The optimal osmotic dehydration process conditions for maximum water loss and minimum solids gain and color variation were determined by the \Response Optimizer" option: 83% sucrose concentration, 20 °C and 9.2 hours. Thus, the best operational conditions corresponded to high sugar concentration and low temperature, improving energy saving and decreasing the process costs.

2018Journal article

Open access

Organic acid profile of chestnut (Castanea sativa Mill.) as affected by hot air convective drying

Publication . Delgado, Teresa; Ramalhosa, Elsa; Pereira, J.A.; Casal, Susana

The objective of the present work was to evaluate the effect of hot air convective drying on the organic acid profile of chestnut. An extractive method, with internal standard, followed by HPLC-UV was validated, allowing the quantification of malic, ascorbic, citric, and fumaric acids with good precision and accuracy. Fresh chestnuts presented differences between varieties. The thermal process caused equivalent losses of ascorbic acid on both varieties, but higher losses of malic acid in Longal. Furthermore, fumaric acid contents increased on both varieties. Therefore, hot air convective drying affected the organic acid composition of chestnut slices, and this effect was varietal dependent.

2018Journal article

Open access

Efeito da secagem por ar quente na cor e propriedades nutricionais de duas variedades de castanha (Castanea sativa Mill.)

Publication . Delgado, Teresa; Pereira, J.A.; Casal, Susana; Ramalhosa, Elsa

O objetivo do nosso trabalho foi avaliar o efeito da secagem por ar quente, realizada num secador de tabuleiros a 50 °C (convecção forçada), nas propriedades físicas e nutricionais de castanha laminada ao longo do tempo de secagem (0, 4, 6 e 10 horas). Verificou-se um aumento na variação total de cor (ΔE) ao longo da desidratação. Contudo, esta mudança de cor não foi visualmente percetível. As alterações na composição nutricional também foram pouco significativas, mesmo após 10 horas de secagem. A variabilidade entre variedades foi maior do que a observada ao longo da secagem para cada variedade, sugerindo que o processo de desidratação não alterou significativamente as propriedades nutricionais da castanha. Devido ao seu baixo teor calórico (cerca de 367 kcal/100 g produto), reduzido teor de gordura e um interessante teor em fibras, além de não conter glúten, a castanha laminada apresenta-se como um excelente snack.

2014Conference paper

Open access