Spray-drying encapsulation of sour guava (Psidium friedrichsthalianum) bioactive compounds: A response surface approach for functional powder development

Introduction: Sour guava (Psidium friedrichsthalianum) is a tropical fruit rich in phenolic compounds, including ellagitannins and proanthocyanidins, with antioxidant and anti‑inflammatory activities (Muñoz‑Arrieta et al., 2021; Navarro et al., 2024). However, its high moisture (~82%) limits shelf life and agroindustrial use. Spray drying encapsulation is an innovative technology to stabilize bioactive compounds (Shishir & Chen, 2017). Maltodextrin (MD) and inulin (IN) are complementary wall materials: MD offers high solubility and low cost, while IN provides prebiotic effects and hydrogen‑bond interactions with phenolics (Mensink et al., 2015). Despite sour guava's potential, no study has optimized its spray‑drying encapsulation with MD and IN, representing a clear knowledge gap. Objective: To optimize the spray‑drying encapsulation of sour guava juice phenolics using MD and IN as wall materials via response surface methodology. Methodology: A rotatable central composite design (2³, α=1.68, 17 runs) evaluated the effects of inlet air temperature (150–180°C), wall material concentration (5–15% w/v), and inulin proportion (20–50% w/w) on process yield, moisture content, hygroscopicity, water solubility index, clarity, and polyphenol encapsulation efficiency. Relative contribution analysis (threshold >10%) was applied for model reduction. The optimal powder was characterized for physicochemical properties, flowability, structural features (FTIR, DSC), morphology, and antioxidant activity (DPPH, ABTS). Results: The optimal conditions (150°C, 14.84% w/v wall material, 50% w/w inulin) yielded a powder with 83.80% encapsulation efficiency and experimental values closely matching predictions (deviation <10%). The powder exhibited low water activity (0.227), adequate flowability (Carr index: 20%; Hausner ratio: 1.25), and high antioxidant capacity (DPPH: 171.71±34.86 µmol TE/100 g; ABTS: 421.17±24.60 µmol TE/100 g). FTIR and DSC confirmed effective encapsulation through hydrogen bonds between phenolic compounds and wall materials (Mensink et al., 2015), and morphology revealed spherical particles with smooth surfaces (7.17–19.26 µm). Discussion: Wall material concentration was the most influential factor on moisture, hygroscopicity, solubility, clarity, and encapsulation efficiency. Increasing it reduced moisture and hygroscopicity while improving solubility and encapsulation efficiency. Inulin enhanced phenolic retention through its hydrophilic structure, though it slightly increased hygroscopicity. Temperature had moderate effects: higher values reduced hygroscopicity but slightly decreased encapsulation efficiency. The reduced models maintained high predictive capacity with greater parsimony. The powder's low water activity and adequate flowability make it technologically viable for industrial applications. Conclusion: Spray drying with MD and IN is a viable technology for sour guava functional powder with high bioactive retention and technological feasibility, contributing to the valorization of this underutilized fruit within a circular economy framework

Funding: This research was self-financed by the authors. The University of Córdoba provided laboratory facilities and equipment.