Ultrasonic-assisted citrus pectin modification in the bicarbonate-activated hydrogen peroxide system: Chemical and microstructural analysis

Weiwei Hu; Shiguo Chen; Dongmei Wu; Jiaqi Zheng; Xingqian Ye

doi:10.1016/j.ultsonch.2019.04.036

Ultrasonic-assisted citrus pectin modification in the bicarbonate-activated hydrogen peroxide system: Chemical and microstructural analysis

Ultrason Sonochem. 2019 Nov:58:104576. doi: 10.1016/j.ultsonch.2019.04.036. Epub 2019 Apr 29.

Authors

Weiwei Hu¹, Shiguo Chen¹, Dongmei Wu¹, Jiaqi Zheng¹, Xingqian Ye²

Affiliations

¹ College of Biosystems Engineering and Food Science, Zhejiang Key Laboratory for Agro-Food Processing, Department of Food Science and Nutrition, Zhejiang University, Hangzhou 310058, China.
² College of Biosystems Engineering and Food Science, Zhejiang Key Laboratory for Agro-Food Processing, Department of Food Science and Nutrition, Zhejiang University, Hangzhou 310058, China. Electronic address: psu@zju.edu.cn.

PMID: 31450350
DOI: 10.1016/j.ultsonch.2019.04.036

Abstract

The modified pectin (MP) showed the improved functional properties than the native one. The aim of present study was to develop the ultrasonic accelerated bicarbonate-hydrogen peroxide system for pectin modification to generate short fragments with advanced bioactive properties. The depolymerization effects of this system on the physicochemical properties, structural features, and bioactivity of the degraded fragments were studied systematically. The results indicated that the molecular weight of pectin was reduced drastically from 1088 kDa to 33 kDa within 50 min under an optimized condition (M_H2O2-M_NaHCO3 = 1:2.5, 50 °C, and ultrasound intensity = 11.4 W/cm³). The resulting fragments also showed lower degree of methoxylation and rheological viscosity. The investigation on the sample structures and active oxygen species demonstrated that the highly active O₂^- species generated from HCO₄^- of NaHCO₃-H₂O₂ acted preferentially on the GalA backbone in the HG region, while the RG-I region was maintained; and ultrasound enhanced the degradation efficiency via both chemical effects (increasing the transformation of free radicals) and mechanical effects (disaggregating polysaccharide clusters). The atomic force microscope (AFM) imaging directly verified the branched-chain morphology of pectin and the small-strand degradation fragments. Moreover, ultrasound and NaHCO₃-H₂O₂ treatment induced high galactose content in the degraded products, contributing to an improved inhibitory activity against A549 lung cancer cells, as shown by MTT assay.

Keywords: Anti-tumor activity; Bicarbonate-activated hydrogen peroxide; Citrus pectin; Depolymerization; Modification; Ultrasound.