Thiolated citrus low-methoxyl pectin: Synthesis, characterization and rheological and oxidation-responsive gelling properties

Jinfeng Chen; Fayin Ye; Yun Zhou; Guohua Zhao

doi:10.1016/j.carbpol.2017.11.053

Thiolated citrus low-methoxyl pectin: Synthesis, characterization and rheological and oxidation-responsive gelling properties

Carbohydr Polym. 2018 Feb 1:181:964-973. doi: 10.1016/j.carbpol.2017.11.053. Epub 2017 Nov 16.

Authors

Jinfeng Chen¹, Fayin Ye¹, Yun Zhou¹, Guohua Zhao²

Affiliations

¹ College of Food Science, Southwest University, Chongqing 400715, People's Republic of China.
² College of Food Science, Southwest University, Chongqing 400715, People's Republic of China; Chongqing Engineering Research Centre of Regional Foods, Chongqing 400715, People's Republic of China. Electronic address: zhaogh@swu.edu.cn.

PMID: 29254061
DOI: 10.1016/j.carbpol.2017.11.053

Abstract

In the present study, citrus low-methoxyl pectin was modified by conjugating cysteine via amide bonds, and the resultant polymer (CYS-PEC) was characterized. CYS-PEC conjugates with thiol contents varying from 77.8μmol/g to 296μmol/g were synthesized, and the successful conjugation was evidenced by elemental, and FT-IR analyses. The sulfur in CYS-PEC is predominately in the thiol form, with a minor fraction forming disulfide bonds (∼15%), which occur when thiol/disulfide interchange interrupts the intended thiolation. Both native and modified pectin dispersions exhibited strong pseudoplastic properties, and the frequency sweeps revealed them to be dispersions containing microgel particles. Dynamic viscoelastic analysis was used to determine the oxidation-response gelling capacities of polymer dispersions containing H₂O₂, especially those that are highly thiolated and have cross-linked gel properties. For oxidation-induced CYS-PEC gels, their gelation time, hardness, viscosity and elastic moduli and swelling-disintegration ratio are dependent on the thiol group content, H₂O₂ concentration and polymer concentration.

Keywords: Citrus low-methoxyl pectin; Cysteine; Gelling property; Oxidation-responsive; Pectin-cysteine conjugate; Rheological property.