氯化钙浸渍对冻干霍山石斛品质影响及其作用机制研究OA

To improve the freeze-drying quality of fresh Dendrobium huoshanense,this study explored the effects of calcium chloride(CaCl2)immersion pretreatment on the physical properties,active components,and underlying mechanisms of freeze-dried samples.The results showed that appropriate CaCl2 treatment enhanced the moisture characteristics,texture,color,and polysaccharide content of freeze-dried samples.Among all treatments,the 3.0%CaCl2 group exhibited the best performance,with a moisture content of 7.40%±0.19%,rehydration ratio of 3.02±0.03,hardness of 2.70±0.23 N,crispness of 1.34±0.11 N·S,and a minimal color difference(ΔE)of 2.02±0.07.Its polysaccharide content reached 32.47%±0.73%,an increase of 10.3%was made compared with the untreated control.Subsequently,the differences between extracted dendrobium pectin and calcium pectate prepared by reacting with CaCl2 were analyzed.FT-IR analysis revealed a shift of the characteristic carboxylate peak from 1 591.2 cm-1 to approximately 1 621.1 cm-1,and NMR spectra showed significant changes in proton signals.The weight-average molecular weight of pectin(414 777 g/mol)increased gradually with CaCl2 concentration(1.5%-6.0%)to 529 211 g/mol.SEM observations showed that the microstructure of calcium pectate changed from loose and collapsed to dense and compact.These findings indicate that Ca2+forms a stable"egg-box"crosslinking structure with pectin in the cell wall,which is the core mechanism for quality improvement.This study provides theoretical and technical support for the high-quality and value-added processing of Dendrobium huoshanense.