Effect of drying methods on the physicochemical and thermal properties of Mexican plum (Spondias purpurea L.)

Abstract

Plum slices (diameter 2.5 cm and thickness 0.2 cm) were dried using vertical tray-drying (VTD) and freeze-drying. Models were used to determine the thermal conductivity (k) and specific heat (Cp). In addition, water activity (aw), colour total change (∆E), pectin yield (ypec) and rehydration capacity were investigated. The moisture content of tray- and freeze-dried plum was relatively significant (p < 0.05). No significant difference was found in terms of aw. There was a maximum decrease in k and Cp of 90% and 91.5% during drying process, respectively. In terms of quality, ∆E showed that tray-dried samples had slight darker (browning), whereas the freeze-dried samples had a lighter colouring compared to the fresh fruit. The quality and rehydration characteristics of freeze-dried plum were higher than that of a tray-dried product; however, VTD could be appropriate for industrial production because of its advantages in lower cost and energy consumption.

Keywords

• Plum
• drying
• physicochemical properties
• thermal properties
• rehydration
• pectin yield