牛蒡茶加工工艺优化及其多糖体外抗氧化活性

为了优化牛蒡茶加工工艺，提升牛蒡茶的品质，并研究多糖体外抗氧化活性。采用微波真空干燥制备牛蒡茶，根据单因素实验和响应面法确定了预热温度、真空度、干燥温度、切片厚度等工艺条件；利用水提醇沉法提取牛蒡茶中的多糖，并用苯酚-硫酸法测定其多糖含量；多糖经脱蛋白、透析和脱色后，经红外光谱分析多糖特征，高效液相色谱测定其单糖组成；体外试验检测多糖对DPPH·、ABTS+·和·OH的清除能力。结果表明:在预热温度75℃，真空度0.07 MPa，干燥温度66℃，切片厚度3 mm条件下，获得的牛蒡茶多糖含量最高，为51.08 mg/g，含水率为7.85%，复水比5.46 g/g；电镜显示牛蒡茶结构紧致匀整，感官品质好；红外光谱分析牛蒡茶多糖具有典型多糖类物质的特征吸收峰；牛蒡茶总多糖含量较原料牛蒡根提高了1.6倍；单糖组分中，葡萄糖含量提高了135倍，甘露糖提高了7倍；牛蒡茶多糖清除DPPH·、ABTS+·及·OH的半抑制浓度（IC₅₀）分别为1.115、1.556和1.047 mg/mL，清除率都能达到65%以上，具有较好的体外抗氧化活性。

Optimization of Processing Technology of Burdock Tea and Antioxidant Activity of Its Polysaccharides in Vitro

The purpose of this study was to optimize the processing technology of burdock tea,improve the quality of burdock tea,and study the antioxidant activity of polysaccharides in vitro. Microwave-vacuum drying was used to prepare burdock tea. The preheating temperature,vacuum degree,drying temperature and slice thickness were determined by single factor experiment and response surface methodology. The polysaccharide in burdock tea was extracted by water extraction and alcohol precipitation,and its content was determined by phenol-sulfuric acid method. The polysaccharide was characterized by infrared spectroscopy and their monosaccharide composition was determined by HPLC after deproteinization,dialysis and decolorization. The scavenging capacities of polysaccharide on DPPH·,ABTS+· and ·OH were detected in vitro. The results showed that the highest content of burdock tea polysaccharide was 51.08 mg/g under the conditions of preheating temperature 75 ℃,vacuum degree 0.07 MPa,drying temperature 66 ℃ and slice thickness 3 mm. The water content of burdock tea was 7.85% and the rehydration ratio was 5.46 g/g. Electron microscope showed that burdock tea had a compact and uniform structure and good sensory quality. Infrared spectrum showed that burdock tea polysaccharide had characteristic absorption peaks of typical polysaccharide. The total polysaccharide content of burdock tea increased 1.6 times higher than that of burdock root. In monosaccharide component the glucose content of burdock tea increased 135 times,and the mannose content increased 7 times higher than that of burdock root. The semi-inhibitory concentrations(IC₅₀)of DPPH·,ABTS+· and ·OH from burdock tea polysaccharide were 1.115,1.556 and 1.047 mg/mL,respectively. The burdock tea polysaccharide had good antioxidant activity in vitro with over 65% scavenging rates.