Paper Number
GG4 

Session
Arrested Systems: Gels and Glasses

Title
Multi-staged progression of the viscoelastic moduli during gelation of Aiyu pectin

Presentation Date and Time
October 11, 2021 (Monday) 11:05

Track / Room
Track 6 / Ballroom 1

Authors (Click on name to view author profile)

  1. Chen, Yeng-Long (Academia Sinica, Institute of Physics)
  2. Wang, Fan-Wei (University of Michigan, Department of Chemical Engineering)
  3. Geri, Michela (Massachusetts Institute of Technology)
  4. Chen, Yun-Ru (Academia Sinica, Institute of Physics)
  5. Huang, Jung-Ren (Academia Sinica, Institute of Physics)
  6. McKinley, Gareth H. (Massachusetts Institute of Technology, Mechanical Engineering)

Author and Affiliation Lines (in printed abstract book)
Yeng-Long Chen1, Fan-Wei Wang1, Michela Geri2, Yun-Ru Chen1, Jung-Ren Huang1 and Gareth H. McKinley2
1Institute of Physics, Academia Sinica, Taipei 11529, Taiwan; 2Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA

Speaker / Presenter 
Chen, Yeng-Long

Keywords
experimental methods; theoretical methods; applied rheology; biological materials; gels; polymer solutions

Text of Abstract

Aiyu is an edible gel dessert made from the extract obtained by washing the seeds of Ficus Pumila var. Awkeotsong, uniquely cultivated in Taiwan. Water is the only component needed in order to make the gel at room temperature. The main gelation components are ions, low methoxyl pectin, and methoxylesterase enzyme. The multivalent ions, in particular calcium, crosslink with pectin polymers to form an elastic network.

During gelation, we observed an inflection point in the storage modulus together with a corresponding frequency-dependent maximum and subsequent plateau in the loss modulus. We characterized the rheological and microstructural evolution with Optimal Window Chirp rheometry (OwCh) and conventional oscillatory shear time sweeps, as well as microstructural characterization with cryo scanning electron microscopy.

Many calcium pectate systems have crosslinks formed by consecutively bonded calcium junction zones, but the length of the junction zones vary from system to system. By considering the reaction kinetics model of a microstructural transformation from transient, short junction zones to longer, more stable junction zones, we developed an ideal rubber network model that captures the characteristics of the viscoelastic moduli progression and their dependence on salt and calcium concentration.