(上海应用技术大学香料香精技术与工程学院 上海 201418)
(School of Perfume and Aroma Technology， Shanghai Institute of Technology， Shanghai 201418)
以铁皮石斛多糖(DOP)为研究对象，通过流变与FT-IR方法，考察多糖质量浓度、温度、体系pH值及金属离子种类与浓度对铁皮石斛多糖的流体性质及凝胶性质的影响。结果表明:在不同质量浓度、温度、金属离子和pH值条件下，DOP水溶液表现出剪切稀释现象。DOP水溶液的黏度随DOP质量浓度的增加而增大；在5~75 ℃范围，DOP水溶液的黏度随温度的升高而降低；Na+的添加显著提高了DOP溶液的黏度，K+、Ca2+、Al3+可降低溶液的黏度，黏度变化趋势与金属离子浓度和价态有关。DOP水溶液在pH 2.0~6.8范围具有良好的稳定性，在碱性条件下，DOP水溶液的黏度显著增加。具体而言，当pH>10.0时，DOP溶液形成真正的凝胶。FT-IR结果显示，凝胶现象可能与1 735，2 935，2 881 cm-1处吸收峰的变化有关。上述结果表明，DOP水溶液具有独特的流体性质和凝胶性质，研究结果对铁皮石斛多糖的制备和加工具有一定的参考价值。
The effects of mass concentration， temperature， inorganic cation type and pH on the fluid and gelation properties of polysaccharide from Dendrobium officinale(DOP) were evaluated by rheological analysis and FT-IR analysis in this study. The results showed that the DOP aqueous solution exhibited shear-thinning flow behavior under different concentration， temperature， inorganic cation type and solution pH. The viscosity of DOP solution increased with its increasing concentration and the pseudoplastic was more obvious. The viscosity of DOP solution decreased with the increasing of temperature in the range of 5~75 ℃. The addition of Na+ significantly increased the viscosity of DOP solution. However， the viscosity of DOP solution was decreased when K+， Ca2+， Al3+ were added respectively and the change trend was related to the inorganic cation concentration and valence. DOP extracted with hot water had good stability under acidic conditions. However， the viscosity of DOP solution significantly increased under alkaline conditions and the gelation of solution will be occurred under alkaline conditions (pH>10.0). The dynamic rheological results showed that the gel transition was enhanced with the increasing of polysaccharide mass concentration. The FT-IR results indicated that the gelation was related to the absorption peaks at 1 735 cm-1， 2 935 cm-1 and 2 881 cm-1. The above results suggested that the aqueous solution of DOP had unique fluid and gelation properties for processing. The results are useful for the formulation and processing of polysaccharide extracted from Dendrobium officinale.