以芹菜渣为原料，采用水提（W），碱提（A）和超声辅助碱提（UA）工艺制备三种可溶性膳食纤维（Soluble dietary fiber, SDF)，并对比其结构及抗氧化活性的差异。通过傅里叶红外光谱（FT-IR）、热分析技术和扫描电镜等表征SDF的结构，结果显示：碱处理可导致酯键断裂，而超声辅助碱处理可裂解醚键致SDF含量增多；W-SDF、A-SDF和UA-SDF的吸热峰温分别为146.99、150.09和153.44 ℃，热稳定性大小为：UA-SDF>ASDF>W-SDF；W-SDF表面光滑紧实，平均粒径最大（1 481 nm），而A-SDF与UA-SDF均呈现多孔疏松的结构，A-SDF粒径次之（841 nm），UA-SDF最小（588.34 nm），这说明通过碱处理和超声处理，可导致酯键和醚键的断裂，进而将不溶性SDF转变为可溶性SDF。三种SDF体外抗氧化活性存在显著性差异（P<0.05），其中UA-SDF对•OH和DPPH•清除能力最强，且IC50分别为0.67和0.31 mg/mL，其次是A-SDF的IC50分别为1.25和0.58 mg/mL，W-SDF的IC50分别为1.72和0.86 mg/mL。综合分析，芹菜可溶性膳食纤维的抗氧化特性差异是由其化学成分和表面结构的差异引起的。

Three types of soluble dietary fibers (SDF) were prepared from celery residue by water extraction (W-SDF), alkali extraction (A-SDF), and ultrasound-assisted alkali extraction (UA-SDF), and the differences in their structure and antioxidant properties were compared. The structures of the SDF samples were characterized by Fourier-transform infrared spectroscopy (FT-IR), thermal analysis techniques and scanning electron microscopy. The results showed that alkali treatment could cause ester bond cleavage, while ultrasound-assisted alkali treatment could increase the content of SDF through breaking the ether bonds. The endothermic peak temperatures of W-SDF, A-SDF, and UA-SDF were 146.99, 150.09, and 153.44 ℃, respectively, and the thermal stability followed the order of UA-SDF>A-SDF>W-SDF. The W-SDF had a smooth and compact surface with the largest average particle size (1 481 nm), whilst the A-SDF and UA-SDF showed porous and loose structures with average particle sizes being 841 nm and 588.34 nm, respectively, indicating that the alkali treatment and ultrasound treatment resulted in the cleavage of ester and ether bonds thereby causing the conversion of insoluble fiber to soluble fibers. The in vitro antioxidant activity results showed significant differences (P<0.05) among the three kinds of fibers. Among them, the UA-SDF exhibited the strongest abilities to scavenge •OH and DPPH• with IC50 values being 0.67 and 0.31 mg/mL, respectively, followed by A-SDF (which had IC50 values of 1.25 and 0.58 mg/mL, respectively), and W-SDF (which had IC50 values of 1.72 and 0.86 mg/mL, respectively). Comprehensive analysis suggests that the differences in the antioxidant properties of the soluble dietary fibers from celery residue were caused by the differences in their chemical compositions and surface structures.

湖南省教育厅科学研究优秀青年项目（22B1094）