Analysis of energy consumption, heat and mass transfer, drying kinetics and effective moisture diffusivity during foam-mat drying of mango in a convective hot-air dryer

Abstract

This study mainly aimed to analyse the energy requirement, consumption and efficiency during foam-mat drying of mango in a convective hot-air drier. Modelling thin-layer drying kinetics was performed to predict drying behaviour and analysed moisture diffusivity, heat and mass transfer in the drying conditions. The effect of drying on some quality characteristics of dried powder was evaluated. The mango fruit was transformed into foam using egg albumin and dried at 60-80 °C with 2–6 mm foam thicknesses. The result showed that the drying rate increased as the drying temperature (DT) increased and foam thickness (FT) decreased. The Logarithmic model was found best to describe the drying behaviour. The effective moisture diffusivity (0.81–5.75 × 10 −9 m 2 s −1 ) increased as the DT and FT increased with an activation energy level of 24.11–26.32 kJ mol −1 , Arrhenius constant values of 1.35–5.77 × 10 −9 m 2 s −1 and R 2 value higher than 0.98. The heat and mass transfer coefficients decreased as the FT increased, but no significant changes as DT increased, corresponding to their values in the range of 33.35–58.0 W m 2 C −1 and 3.51–6.41 × 10-2 m s −1 . The specific energy consumption decreased whereas total energy required, thermal, and energy efficiency increased as the FT and DT increased; corresponding their values were in the range of 20.58–41.03 kWh kg −1 , 12.5–27.41 kWh, 7.26–21.32% and 1.3–2.56%. Mango powder's quality characteristics (pH, vitamin C, β-carotene and total phenolic contents) were significantly decreased as the DT and FT increased. Still, the total soluble solids and rehydration capacity did not affect statistically. • Energy requirement for foam-mat drying of mango was evaluated experimentally. • Drying conditions significantly affected energy consumption, thermal & energy efficiency. • Logarithmic model was found best to describe drying behaviour among drying kinetics. • Effective moisture diffusivity was raised as drying temperature and foam thickness increased. • Heat and mass transfer coefficients decreased as foam thickness increased.