Ultrasound-assisted spray freeze-drying: a cutting-edge approach for gum Arabic cryogel powder production

Gum Arabic is a multifunctional natural polysaccharide that is widely used in the food and pharmaceutical industries, but its powdered form often exhibits poor structural and functional properties. Recent advances in spray freeze-drying (SFD) and ultrasound-assisted spray freeze-drying (US-SFD) present promising strategies for improving powder quality. While prior studies have explored basic SFD applications, limited attention has been paid to the impact of ultrasound during freezing on gum Arabic's structure and functionality. This study aimed to evaluate how US-SFD affects the physicochemical and structural characteristics of gum Arabic cryogels at 1 and 3 % concentrations. Feed solutions were atomized into liquid nitrogen and freeze-dried, with ultrasound applied during freezing for selected samples. Bulk and tapped density, porosity, thermal behavior, morphology, crystallinity, color, and solubility were evaluated. US-SFD-1 % and US-SFD-3 % exhibited the lowest bulk densities (0.003 ± 0.000 and 0.006 ± 0.002 g/cm³) and highest porosities (up to 99.660 ± 0.086 %), indicating the formation of highly porous, lightweight powders. FTIR revealed reduced O-H stretching intensities in US-SFD samples, suggesting alterations in hydrogen bonding, while XRD confirmed their amorphous nature. Color analysis showed SFD-1 % had the highest ΔE (25.260 ± 2.936), though SFD-3 % appeared more yellow. However, the study was limited by the absence of ultrasound intensity optimization and the evaluation of only a narrow concentration range. Future investigations should focus on a more comprehensive exploration of processing parameters and assess the functional applications of these cryogels in food, pharmaceutical, and biomedical industries.