干制被广泛应用于荔枝的保藏和精深加工，但是干制会导致多糖结构的变化以及生物活性的改变。为了探究热风干制对荔枝果肉多糖的影响，本研究通过分析多糖基本成分、分子量分布、紫外光谱、特征粘度等比较了热风干燥前后鲜荔枝果肉多糖（LPF）和干荔枝果肉多糖（LPD）的理化特性；采用DPPH、ABTS、Fe3+还原抗氧化力（FRAP）和氧自由基清除能力（ORAC）4种方法比较两者的抗氧化活性差异。结果表明，经过干制加工后，荔枝果肉多糖的中性糖含量降低，蛋白含量增加，多糖分子发生裂解，特征粘度下降，抗氧化活性显著提高，其中LPD的FRAP和ORAC值分别是LPF的8.98和4.35倍，LPF和LPD的DPPH?清除能力的IC50值分别是1.98和0.11 mg/mL，两者在4 mg/mL终浓度清除ABTS+?百分率分别是21.87%和98.81%。由此表明热风干制能够显著影响荔枝多糖的理化特性，进而增强其抗氧化活性。

Drying is commonly used for preservation and processing of litchi. However, its polysaccharide structure may be altered by drying, resulting in biological activity changes. In order to study the effect of hot-air drying of litchi polysaccharides in the pulp, the physicochemical properties and antioxidant activity of polysaccharides from fresh (LPF) and dried litchi pulp (LPD) were investigated, respectively. The results showed that the protein content of LPD was higher than that of LPF, contained less neutral sugar and lower intrinsic viscosity. LPD exhibited high antioxidant activity in DPPH? scavenging activity (IC50 value 0.11 mg/mL), ABTS+? scavenging activity (98.81% at 4 mg/mL) while LPF were 1.98 mg/mL and 21.87%, respectively. In addition, the FRAP and ORAC value of LPD were 8.98 and 4.35 folds of those of LPF, respectively. In summary, the drying process of litchi can effectively change the chemical structure of polysaccharides to improve their antioxidant activity.

国家自然科学基金-广东联合基金重点项目（U1301211）；国家973项目（2012CB722904）；国家十二五科技支撑计划（2012BAD33B10）