Effects of steam explosion pretreatment at different severity factors on the structure, chemical composition, and digestive properties of Dendrobium officinale (Tiepishihu) polysaccharides

The bioactive molecules of Dendrobium officinale , an edible medicinal plant native to China, comprise mainly polysaccharides, which exhibit diverse physiological activities. However, the rigid cell wall structure of D. officinale hinders their efficient release. Steam explosion (SE) is an effective pretreatment technology for disrupting the cell walls of raw materials. In this study, the effects of SE at severity factors (SF) of 3.50 and 3.91 on the yield of D. officinale polysaccharides were evaluated. Additionally, the structural features, chemical composition, and antioxidative activities of polysaccharides from SE-treated D. officinale (SEDOPs) before and after in vitro digestion were analyzed. Compared with the untreated group (DOP), the SE-treated samples exhibited enhanced polysaccharide release rates. Additionally, SEDOP 3.50 was significantly purer and had a higher uronic acid content than that of DOP. SE treatment also reduced molecular weights of the polysaccharides. Mannose and glucose were identified as the predominant monosaccharides, with SE altering their molar ratios. Structurally, the SEDOPs developed porous architectures while their primary structures remained preserved. Their triple-helical conformations were disrupted following intestinal digestion. Furthermore, SE treatment enhanced their antioxidative capacities, with SEDOP 3.50 consistently exhibiting the highest uronic acid content and strongest antioxidative activity throughout the digestion process.