Development and Comparison of Drying Tropical Herbal Strategies for Annona muricata Leaves: Integrating of Effective Moisture Diffusivity Using Antioxidant Activity, FTIR Ratios, and Color Attributes

Drying strategy employed exerts a significant influence on the kinetics and functional quality of Annona muricata (soursop) leaves. However, the current literature offers a paucity of practical, non-destructive indicators to inform process decisions. The present study sets out to compare sun drying (SD), room-temperature drying (RTD), convective tray drying (CTD; 40-60 °C), and microwave drying (MWD; 120-380 W), models thin-layer curves, and integrates effective moisture diffusivity (D_eff) with quality metrics-antioxidant activity (IC₅₀, DPPH), FTIR ratios (R_Q, R₁-R₃), and color attributes (ÎE, a*). Multi-parameter models have been shown to outperform simpler forms. The Midilli model provided the most precise global fit (R² > 0.95; RMSE < 0.05), while Jenna-Das performed well in specific convective subsets. As the temperature/power were increased, D_eff increased and reached a peak at an MWD of 380 W. This resulted in an approximate acceleration of ~225à compared to the CTD 50 °C and a drying time of approximately â 4 min. A clear trade-off emerged: CTD 40 °C exhibited a preserved appearance (ÎE â 2.7) but under-retained phenolics (weaker IC₅₀), whereas CTD 60 °C and MWD 380 W produced higher ÎE (> 8) yet superior FTIR ratios (R_Q, R₁-R₃) and stronger antioxidant activity; mid-power MWD (120-250 W) was detrimental. The colorimetric-spectroscopic linkages were found to be quantitative, with ÎE-IC₅₀ exhibiting a weak-moderate relationship, and a* demonstrating a strong colleration with R_Q (R² â 0.73). Chemometrics (PLSR with VIP) identified R_Q/R₃ as dominant predictors (R²LOOCV â 0.33), thereby converting FTIR from descriptive readout to an actionable inline/at-line QC. Collectively, these results establish a predictive quality-control framework-using ÎE and a* with R_Q-for efficient selection, development, and implementation of tropical herbal drying technologies, and provide actionable set-points (optimal: MWD 380 W; convective alternative: CTD 60 °C) that balance speed and bioactive retention. © 2026, Walailak University. All rights reserved.