Foam-mat drying characteristics of overripe banana pulp using superfine (< 100 µm) fraction of defatted soybean flour as foaming agent

In tropical and subtropical countries, an enormous amount of fruits and vegetables are produced, which are extremely attractive from a commercial point of view, a typical example being the banana.Preservation methods such as drying are of great relevance to increase the shelf life and commercial value of fruit and their derivatives.This investigation aimed to study the drying kinetics of overripe banana fruits at three different drying air temperatures and calculate the effective moisture diffusivities of FMD banana powders, evaluate the effect of concentration levels of defatted soybean flour as foaming agent on the stability and drying kinetics of overripe banana foam-mats.Banana powders were prepared using overripe banana paste incorporating defatted soybean flour (DSF) as foaming agent at a mass concentration of 10%, 15% and 20% (w/w), and drying the resultant foams until a constant moisture content was reached.The maximum foam expansion (87.50%) and foam stability (98.55%) of DSF were found after 5 min whipping.The total drying time required to achieve up to a constant moisture level was 9 hours, 4 hours and 3 hours for 55 o C, 70 o C and 85 o C drying air temperatures, respectively.The fitted logarithmic model was found to be best in almost all cases.The effective moisture diffusivity increased with increasing temperature from 1.6510 -6 m 2 /s to 9.4610 -6 m 2 /s, but decreased with the increase in the incorporation rate of DSF.Based on the above parameters, it was resolved that foam mat drying using 10% DSF at 70 o C air-drying temperature was the best combination.