Comparative Analysis of Drying Techniques for Custard Apple Pulp: Hot Air, Vacuum, and Microwave-Assisted Methods

The drying characteristics of custard apple pulp were investigated using three different drying techniques: hot-air tray drying, vacuum tray drying, and tray combined with microwave drying. The effects of drying temperature (45, 50, and 55°C) and maltodextrin addition (0, 15, 20, and 25%) on the drying kinetics, solubility index, dried product recovery percentage, and color values (L*, a*, and b*) were evaluated. Non-linear regression analysis was performed to fit the experimental data to seven thin-layer drying models. The Hii model best described the drying behavior of custard apple pulp, which was dried using a hot-air tray dryer and tray combined with a microwave dryer, whereas the Midilli et al. model was most suitable for the vacuum tray dryer. The drying time was significantly reduced by increasing the temperature and using a vacuum dryer (240 to 420 min) followed by a tray combined with a microwave dryer (394 to 420 min). The addition of maltodextrin improved the solubility index and recovery percentage of the dried pulp. The L* value, solubility index, and product recovery ranged from 54.56 to 69.59%, 49.23 to 69.72%, and 20.83 to 50.25 %, respectively. The vacuum dryer and tray combined with the microwave dryer showed potential for industrial applications because of their shorter processing times. This study provides valuable insights into optimizing the drying process of custard apple pulp and selecting appropriate drying techniques for commercial preservation while maintaining the quality attributes of the product.