Antioxidant activity and emulsifying properties of Dendrobium officinale polysaccharides with distinct structural characteristics

This study compared six extraction techniques, hot water, acid-assised, ultrasound-assisted, microwave-assisted, UV/H₂O₂-assisted, and enzyme-assisted on the structural, antioxidant, and emulsifying properties of Dendrobium officinale polysaccharides (DOPs). Molecular weights ranged from 1155.239 kDa (DOPs-hwe) to 3.139 kDa (DOPs-ee). DOPs-hwe showed the highest uronic acid content (4.52 %) and excellent emulsifying ability (89.2 % activity, 81.5 % stability). In contrast, DOPs-ae and DOPs-ee exhibited stronger antioxidant activity, with DPPH scavenging rates of 52.36 % and 58.05 % (15 mg/mL), linked to lower molecular weights and higher carboxyl group contents (0.58–0.66 mmol/g). FTIR and Congo red analyses confirmed differences in triple-helix conformations. SEM imaging revealed morphological diversity, from dense (DOPs-hwe) to porous (DOPs-ee). Monosaccharide composition varied across extraction methods. Emulsifying performance was mainly influenced by hydrophobic and steric interactions. These findings provide a useful reference for selecting suitable extraction approaches to tailor DOP functionality for specific applications in food, cosmetic, and pharmaceutical industries.