Drying kinetics of bananas by natural convection: Influence of temperature, shape, blanching and cultivar

Abstract

The influence of variables as temperature, solid shape, temperature, branching and cultivar on drying of bananas were studied. Bananas from cv. Prata and D'água, on disk and cylindrical shape, blanched or not, were dehydrated in a tray dryer in natural convection at 40 and 70 o C. Drying behavior was analyzed by using a mathematical model. The exponential model showed good agreement to experimental data (r 2 0.93 -0.99 and standard error: 0.01-0.05). Temperature presented positive influence on drying rate in all the tested conditions. With respect to the sample shape, the disk shape carried out to significantly higher drying rates only for D'água cultivar without blanching. Blanching was significantly influent, with positive influence, on drying rate of banana cv. Prata at 40º C. The influence of the cultivar did not present a defined tendency.Index terms: Fruit, dehydration, pretreatment. RESUMONo presente trabalho, estudou-se a influência de variáveis como temperatura, formato do sólido, branqueamento e cultivar na secagem de bananas. Bananas cultivares Prata e D'água, nos formatos disco e cilindro, branqueadas ou não, foram desidratadas em secador de bandejas com convecção natural nas temperaturas de 40 e 70 o C. O comportamento da secagem foi analisado utilizandose modelagem matemática. O modelo exponencial mostrou bom ajuste aos resultados experimentais (r 2 : 0,93 -0,99 e erro de estimativa padrão: 0,01 -0,04). A temperatura apresentou influência positiva na taxa de secagem em todas as condições testadas. Com relação ao formato das amostras, o formato disco conduziu a taxas de secagem significativamente maiores somente para o cultivar D'água e sem branqueamento. O branqueamento se mostrou significativamente influente, com influência positiva na taxa de secagem da banana Prata a 40º C. A influência da cultivar não apresentou uma tendência definida.Termos para indexação: Fruta, desidratação, pré-tratamento.

Use of Ultrasound in the Distilled Water Pretreament and Convective Drying of Pineapple

“…Hence, the time needed to reduce the weight sample to 80 % of its initial weight at 70°C (3.8 ± 0.2 h for P0-D70) was the 31 % of the needed at 40°C (12.2 ± 0.9 h for P0-D40). The effect of temperature on drying rates is well reported in literature [5,12,28,47]. The internal resistance to moisture transport decreased with increasing drying temperature; this was caused by an increase in the mobility of water molecules within the food product.…”

“…The dehydrated product could be used as a ready-to-eat product or as an ingredient in other foods such as snacks, breakfast cereals, pastries and desserts [5,7,20]. Besides, the dried fruits is associated with improvement in the diet and reduction in obesity [31].…”

Cinética de secagem, contração volumétrica e análise da difusão líquida do figo (<italic>Ficus carica</italic> L.)

“…Constantes do modelo Polinomial e os valores do coeficiente de determinação (R², %), erro médio estimado (SE, adimensional) e relativo (P, adimensional) e qui quadrado (χ², adimensional) do modelo para elaboração das curvas de contração volumétrica sobre a cinética de secagem do figo. Como observado por Borges et al (2011) -10 e 9,19 x 10 -10 m² s -1 . Segundo Madamba et al (1996) os valores para difusão líquida de produtos agrícolas estão na ordem de grandeza de 10 -9 a 10 -11 .…”

The Influence of Ethanol and Vacuum on Okara Drying

“…The increase in air temperature resulted in larger driving forces for heat transfer and water evaporation [24]. This effect was observed by [5,10] during the drying process of pineapple and banana, respectively. The use of reduced pressures in vacuum drying improves the drying time (C80 and V80).…”

“…It is considered a simultaneous heat and mass transfer process, wherein water is transferred by diffusion from the interior of the food to the air-food interface and by convection from the food-air interface [9]. However, convective drying requires a large period of time [10].…”