Enhancing mangosteen peel drying: Impact of ethanol pre-treatment, vacuum pulsing, and blaching on process efficiency and bioactive compound levels

The processing of mangosteen yields a substantial volume of waste material. One efficient method for harnessing the potential of mangosteen peels is through their exposure to a drying process. This study investigated pre-treatment methods, ethanol (E), blanching (B), and vacuum pulsing (V), individually and in combination, to mitigate the effects of temperature during the drying of mangosteen peel. The mangosteen peels were dryied, three different models were employed to fit the experimental data: the empirical models of Page and Midilli, and a diffusive model with type I boundary conditions. The combination of pre-treatments (BE, BV, and BEV) at 80 °C significantly reduced drying time to 95 min. Furthermore, the pre-treatments led to reductions in the activation energy (Ea), enthalpy, and Gibbs free energy compared to the control sample (C), while entropy increased. The pre-treated samples exhibited a lighter reddish hue compared to the C sample. The pretreatments had significant effects on the levels of total phenolic compounds (TPC), anthocyanins (A), and flavonoids (F). The BEV sample exhibited notable increases, reaching up to 101% for TPC, 47% for A, and 97% for F at a drying temperature of 80 °C. The combination of pre-treatments B, E, and V resulted in the production of high-quality flour.