Influence of variable temperature drying on red beetroot chips drying kinetic parameters and specific energy consumption

In this work, variable temperature drying regimes, mass of the samples, and the blanching pretreatments were varied to determine the influence of these parameters on the kinetics and specific energy consumption of red beetroot chips during convective drying. Beetroot samples used for the analysis were fresh and blanched slices of 5 mm thickness. Three different temperature regimes were used during drying experiments: first regime (I) was drying at a constant temperature of 70?C, second regime (II) was performed with two-stage drying at temperatures of 80?C and 55?C, and third regime (III) was conducted with three-stage drying at temperatures of 80?C, 60?C, and 55?C, respectively. Results obtained from the experiments were analyzed from the aspects of equilibrium moisture content, drying time, specific energy consumption and drying kinetics including determination of effective moisture coefficient. It was concluded that stage drying strongly affects equilibrium moisture content, while blanching pretreatment increases initial moisture content. The drying time was strongly dependent on the initial mass of the samples, while the energy consumption was depended, besides on the mass, also on drying regime, and it was found to be smallest for two-stage drying. Visually, beetroot had the typical red color for all samples at the beginning, with notable shrinkage effect at the end of the drying process.