Composition and distribution of phenolic compounds of optimized bilberry microcapsules using wood hemicelluloses as protecting materials

Bilberry anthocyanins, known for their antioxidant and functional properties, are highly sensitive to processing conditions, which limits their applications in the food and nutraceutical industries. In this study, we systematically optimized the encapsulation efficiency (EE) of spray-dried bilberry anthocyanins using wood-derived hemicelluloses-galactoglucomannans (GGM) and glucuronoxylans (GX)-as protective materials. We evaluated how spray drying parameters, specifically inlet/outlet temperatures and hemicellulose concentrations, affect anthocyanin retention during spray drying. The results showed that increasing the inlet temperature (140-170 °C) improved EE by approximately 20 %, with GGM achieving a higher EE (86 %) compared to GX (81 %) under optimal conditions. Chromatographic analysis confirmed a 100 % recovery of individual anthocyanins, while confocal laser scanning microscopy demonstrated their homogeneous distribution within the microcapsules, ensuring product quality. Additionally, the microcapsules exhibited a spherical morphology with minimal surface anthocyanin distribution, enhancing their stability against environmental stressors. Raman spectroscopy provided further evidence of anthocyanin-hemicellulose interactions, assumingly non-covalent binding mechanisms such as hydrogen bonding and hydrophobic interactions. These findings advance knowledge on process optimization for anthocyanin microencapsulation using hemicelluloses as protective materials and highlight advanced characterization techniques for food microcapsules.