Microencapsulation of Moringa oleifera leaf extract using food-grade biopolymers: A study on structure, stability and functionality

The encapsulation of phenolic compounds is a promising strategy to improve the stability and bioactivity of plant-based extracts for application in functional foods. This study aimed to encapsulate bioactive compounds extracted from Moringa oleifera leaves using gum arabic (GA) and maltodextrin (MDX), both food-grade carriers, via freeze-drying technique. These biopolymers were selected due to their non-toxic nature, emulsifying properties, and thermal resistance. The encapsulation performance was evaluated in terms of process yield, encapsulation efficiency, total phenolic compounds (TPC) and total flavonoid content (TFC), antioxidant activity, and physicochemical characteristics such as microscopical, FTIR and thermal analysis. The freeze-drying process resulted in a high yield (83 ± 3%) and encapsulation efficiency for TPC (78 ± 2%). The resulting microcapsules exhibited fine particle size (D₅₀ = 1.6 ± 0.1 µm). TPC and TFC were 21 ± 4 GAE mg/g and 12 ± 2 CE mg/g (dry basis), respectively. Antioxidant activity, assessed through DPPH and ABTS assays, showed IC₅₀ values of 171 ± 9 µg/mL and 102 ± 5 µg/mL, respectively, indicating strong radical scavenging potential. Microscopic analysis revealed irregular but compact particle morphology. FTIR spectra confirmed the presence of phenolic compounds, with characteristic O–H and C=O stretching bands, as well as evidence of hydrogen bonding interactions between the core and wall materials. Thermogravimetric analysis demonstrated good thermal stability, with major decomposition events above 220°C and structural integrity maintained below 180°C. In conclusion, freeze-drying with GA and MDX proved effective in preserving the chemical and thermal stability of M. oleifera leaf phenolics, supporting their potential use in thermosensitive functional food formulations.