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Effects of Drying Parameters on Dehydration of Green Banana (musa Sepientum) and Its Use in Potato (solanum Tuberosum) Chips Formulation

M. S. Islam
Department of Food Technology and Rural Industries, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

M. A. Haque
Department of Agro-processing, Bangabandhu Shaikh Mujibur Rahman Agricultural University, Gazipur-1706, Bangladesh

M. N. Islam
Department of Food Technology and Rural Industries, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Abstract/ Executive Summary:

The present study quantifies the drying kinetics of green banana during mechanical dehydration. The effect of loading density (sample thickness) and the temperature on the drying rate constant and drying time were investigated and quantified. Drying rate increased with increasing temperature but decreased with increase in loading density. The values of exponent ‘n’ of the two parameters power law model describing the drying rate constant (as a function of thickness) were less than 2 which indicated the presence of significant external resistance to mass transfer despite the dominance of internal mass transfer resistance. Investigation with three drying air temperatures (55, 60 and 65^oC) at constant air velocity (0.6 m/sec) resulted that the increase in drying air temperature increased the drying process. The moisture diffusivity values were 1.25×10-10, 1.67×10-10 and 2.19×10-10 m²/sec at 55, 60 and 65^oC respectively. The activation energy (Ea) indicating the temperature dependence of the diffusivity was 51.21 KJ/mole obtained using Arrhenius model. Mixing of green banana flour in the potato chips formulation enhanced the fiber and mineral content in the product.

Keywords: Drying rate constant, Moisture diffusivity, Drying kinetics, Loading density, Activation energy

Location: Food Technology and Rural Industries, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Start Date:

End Date:

Program Area: Postharvest and Agro-processing

Commodity: Banana, Potato

Objectives:

To quantifies the drying kinetics of green banana during mechanical dehydration

Methodology:

Good quality green bananas (Musa sepientum), potato powder, starch, wheat powder and soybean oil were collected from the local market. A cabinet dryer (OV-165, Gallenkamp Company) was used for drying of banana slices. The velocity of drying air was kept constant at 0.6 m/sec. A temperature range of 55 to 65°C was used. Excessively high temperatures were not used to avoid the possibility of nutrient loss and of case hardening. Loading densities of 4, 6 and 8 kg/m² of crushed banana (corresponding initial thickness were 5, 7.5 and 10 mm respectively) were dried at 65^oC to determine the effect of loading on the drying rate. After washing in clean water, each banana was cut into 3 to 4 pieces which were then blanched in boiled water for 5 minutes and peeled manually. Subsequently, they were sliced into 3 mm uniform pieces by a mechanical slicer. These sliced pieces were then dipped into 0.2% KMS solution for 10 minutes to enhance the color of the finished product. The slices were dried in a cabinet dryer for about 8 hours at 65^oC. Finally, the banana flour was obtained by grinding the dried banana pieces in a flour mill and packed in polyethylene bags for further use. Precaution was taken carefully to avoid any mixing with other materials during grinding and packaging. Five formulations of chips were prepared using five different ratios of potato and green banana powder. The ratios of potato powder and green banana powder were 70:30 (Type-111), 60:40 (Type-222), 50:50 (Type-333), 40:60 (Type- 444), and 30:70 (Type-555). A control sample without banana flour was also prepared. In each formulation of chips, 10% starch and 10% wheat flour were added to impart better crunchiness and crispiness. The measured amounts of potato powder, green banana powder, starch and wheat flour were mixed and heated in water for 3 to 5 minutes to gelatinize the dough. Thereafter, salt at the rate of 1.5 kg per 100 kg of chips was added in the mix (Reddy and Das, 1993). Small amount of spices were added to improve the aesthetic value of the chips. The entire mix was finally blended using a blending machine (B50, Guangzhou China youjia Machinery Co.) to prepare the dough. Then the dough was spread out on a clean polyethylene paper and cut into 30×25×0.5 mm slabs. After drying at 65^oC for 3 hours these slabs were fried in good quality soybean oil at 165^oC for 2-3 minutes in order to reduce the final moisture content to 2-3%. The resultant chip s had appealing golden brown color. Moisture, ash, fat, protein, total carbohydrate, crude fiber and vitamin C of the green banana flour, potato flour as well as chips were determined by the methods described by Rangana (1992). The calorie values of the samples were also determined by Bomb calorimeter. Experimental Data was analyzed using different stander equations.

Source of Information: The Agriculturists 10 (1): 87-97 (2012) ISSN-1729-5211, A Scientific Journal of Krishi Foundation

Article Link (Online Journal): http://www.banglajol.info/index.php/AGRIC/article/view/11069/8096

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The study revealed that appropriate conditions of dehydration would enhance the drying performance of mechanical dryer. In case of temperature setting, 65°C drying temperature is suggested to get faster drying of green banana without any irregular burning or stake burning. In case of thickness, it was found that the thinner were the slices the faster was the drying rate. Lower loading density resulted in faster drying rate than the higher ones. Activation energy (Ea) for diffusion of water for green banana pieces was found to be 51.21 KJ/mole. The typical moisture diffusivity values were found to be 1.25×10-10, 1.67×10-10 and 2.19×10-10 m²/sec at 55, 60 and 65^oC respectively. Addition of green banana flour has positive impact on the nutritive values of the potato chips. It enhanced the fiber and mineral content of the chips.

Knowledge Management: Journal