Foam-Mat Drying Characteristics of Custard Apple Pulp

Abstract

In the present study, foam mat drying of the custard apple pulp have been conducted by using Glycerol monostearate (GMS) (0.5%, 1.5%, 2.5%, 3.5% and 4.5%) as foaming agent and 0.5% methyl cellulose (MC) as the stabilising agent with whipping time of 2, 4, 6, 8 and 10 minutes. Drying was carried out in a cabinet tray dryer at five different drying temperatures (50, 60 and 70 C) with foam thickness of 2, 4 and 6 mm. The optimum foaming conditions providing foam expansion of (61.11%), foam stability (94%) and lowest foam density (0.60 gm/cm 3) was found to be 3.5% GMS with 0.5% methyl cellulose whipped for 6 minutes. The tray drying of foamed pulp took 240-450 minutes whereas the non-foamed pulp took 420 to 450 minutes saving about 180-240 minutes drying time. Among all the parameters studied, the combination of 3.5% GMS and 0.5% methyl cellulose whipped for 6 min dried at 60 C with foam thickness of 4 mm was found to be the best treatment for custard apple powder preparation.