Study of Foam Stability and Effective Moisture Diffusivity in Mango Foam during Drying

Foam-mat drying is the technique to reduce the drying time which the porous structure of the foam. Porosity in food is important to not only food quality but also effective transport property. This work was therefore aimed to study the drying kinetics of mango foam. The mango puree containing total soluble solids content of 16-18 Brix was whipped to form stable foam by adding methyl cellulose as a foaming agent. The mango foam densities prepared in a range of 0.3 - 0.8 g/cm3 were dried at the drying temperatures of 60 – 80 oC and air velocity of 0.5 m/s. The mango foam mat was done in a short cylinder with a size of 5 mm thickness and 4 cm diameter. The final moisture contents of dried mango foam were 0.12 and 0.04 kg/kg dry basis respectively. The experimental results showed that using methyl cellulose did not show up the drainage of foam, but it still appeared the increase of bubble sizes as viewed by digital microscope. The drying of mango foam mat was in falling rate period. A model of heat and mass transfer was used to determine the effective moisture diffusivity and it was related by Arrhenius equation. The effective moisture diffusivity of mango foam mat in the lower foam density was significantly higher than higher foam density