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Drying Kinetics and Sorption Behavior of Two Varieties Banana (sagor and Sabri) of Bangladesh

M.H. Rahman
Police Super Office, Jhalokathi, Bangladesh

M.W. Ahmed*
Department of Agricultural Engineering, Sher-e-Bangla Agricultural University Dhaka-1207, Bangladesh

M. N. Islam
Department of Food Technology and Rural Industries, Bangladesh Agricultural University, Bangladesh

Abstract/ Executive Summary:

The study was concerned with determining the drying kinetics and sorption behavior of two varieties ripe banana of Bangladesh namely, Sagor and Sabri. The fresh ripe banana collected from the local market were sliced into three different thicknesses (4 mm, 6 mm and 8 mm) and dried at 45°C, 55°C and 65°C in a cabinet dryer. The result showed that the drying rate increases with the increase in temperature and decreases with the increase in slice thickness. The sorption properties of dried banana were studied over a wide range of water activity (0.11-0.93). The BET and GAB models were fitted to the sorption data. It was found that both varieties gave sigmoid (type II) shape isotherm and GAB equation gave the much higher value of monolayer moisture content compared to BET equation. The chemical compositions of fresh and dried banana were determined. The dried products gave substantially higher solid content as well as protein, ash and carbohydrate.

Keywords: Drying rate, Sagor, Sabri, Temperature, Thickness, Moisture sorption.

Location:

Start Date:

End Date:

Program Area: Variety and Species

Commodity: Banana

Objectives:

The goal of this work was the study of the influence of slice thickness and temperature in drying kinetics of bananas in a mechanical dryer, as well as knowing the proximate composition of fresh samples before drying. Sorption behavior of dried bananas was also studied as well as prediction of moisture adsorption by BET and GAB models.

Methodology:

Samples and Equipment Fresh bananas of Sagor (Musa sapientum, AAA genome) and Sabri (Musa sapientum, AAB genome) were purchased from the local market (Mymensingh, Bangladesh). Fruit selection was done by visual inspection where initially ripened bananas were used for proximate composition analysis and drying. Cabinet dryer (Model OV-165, Size-three, Gallen Kamp Company) was used for the dehydration of banana slices. The dryer has a heater installation where the air blows by a fan over the trays containing the samples to be dried. The velocity of air was recorded (0.6 m/sec) by an Anemometer, which was maintained throughout the drying period. Proximate Composition Analysis Fresh ripe banana of two varieties (Sagor and Sabri) were analyzed for moisture, carbohydrate, protein, fat and ash content as per the methods of AOAC (2016) and Ranganna (1992). All the trial were done in triplicate and the results were taken as the average value Mechanical drying Fresh Sagor and Sabri banana were sliced at 4 mm, 6 mm and 8 mm by potato slicer and placed in numbered trays of dryer. For observation of thickness and temperature effect on drying rate, banana slices were dried at three different temperatures (45°C, 55°C and 65°C) at constant air velocity (0.6 m sec^-1). The initial moisture content of all samples was determined previously. The mass change of samples during drying over specific time interval was recorded to calculate moisture ratio that needed to calculate the drying rate. Analysis of sorption behavior The moisture sorption properties of dried bananas were determined at room (25°C) temperature under conditions of various relative humidity (11-93% R.H) in the vacuum desiccators. The various RH conditions were achieved in vacuum desiccators using saturated salt solutions (ASTM E104-02). The method involved putting accurately weighed 3 gm dried and crushed sample in a previously weighed Petridish into desiccators contained saturated salt solutions. An external pump was used to evacuate the desiccators less than 50 torr. After placing into desiccators, the sample weight was taken continuously until it reached to a constant weight. All the trials were done in triplicate and the results were taken as average value. The monolayer moisture content for the moisture adsorption process was determined using the BET and GAB linear model, by linear regression using the Microsoft Office Excel 2007 software. The coefficient of determination (R2) were used to compare the goodness of fit of both modes.

Source of Information: SAARC J. Agri., 16(2): 181-193 (2018)

Article Link (Online Journal): DOI: https://doi.org/10.3329/sja.v16i2.40269

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The study was conducted to determine the effects of thickness and temperature on drying rate of ripe bananas (Sagor and Sabri varities) during mechanical drying. A smaller thickness of 4 mm with higher temperature of 65°C was found the best condition for drying of both verities. Proximate composition of dried bananas was also investigated. According to the moisture absorption data, both varieties gave sigmoid (type II) shape isotherm and more susceptible to decay after 0.75 water activity. Finally, the GAB model was highlighted over BET model for its ability to predict moisture sorption isotherm of both banana flours at room temperature (25°C).

Knowledge Management: Journal