Microencapsulation of Kratom Leaf Extract via Spray Drying: Impact of Inlet Temperature and Wall Materials on Stability and Shelf Life

Abstract

Microencapsulation offers a sustainable approach to improving the stability, functionality, and shelf life of bioactive compounds in food systems, reducing product waste and enhancing resource efficiency. The objectives of this study were to microencapsulate kratom leaf extract (KLE) using spray drying with gum arabic (GA) and resistant maltodextrin (RMD) at two inlet temperatures (150 and 160 °C), to evaluate the resulting microcapsules in terms of their physicochemical properties and assess bioactive retention, specifically total phenolic and flavonoid contents, as well as antioxidant activity, and to investigate stability and shelf-life prediction using kinetic modeling. The resulting microcapsules were evaluated for physicochemical properties, bioactive retention, antioxidant activity, and storage stability. Encapsulation yield ranged from 45.3–62.7%, while encapsulation efficiency was 70.8–83.5%, with GA at 160 °C showing the highest performance. Moisture content remained within 2.1–3.6%, and solubility ranged from 82.4–92.1%, with RMD providing greater solubility and lower residual moisture. Total phenolic content retention ranged from 65.2–79.6%, while total flavonoid retention was 61.4–76.8%. Antioxidant activity (DPPH inhibition) decreased by approximately 20% during processing, with GA at 160 °C preserving the highest activity. Storage studies showed that water activity remained below the stability threshold (aw = 0.30), and first-order kinetic modeling predicted a shelf-life extension of up to 90 days under ambient conditions. Morphological analysis revealed spherical particles with smooth surfaces at 160 °C, whereas higher temperatures induced surface collapse and shrinkage. Overall, GA provided superior protection of phenolics and antioxidants, while RMD enhanced solubility and reduced residual moisture. The findings highlight the potential of using food-grade wall materials and optimized spray drying conditions for scalable production of stable KLE microcapsules suitable for functional food and nutraceutical applications.