The influence of charge on the multiple thermal transitions observed in xanthan

Amir Abbaszadeh, Mita Lad, Gordon Morris, William MacNaughtan, Graham Sworn, Tim Foster

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Helix-coil transitions in xanthans occur at lower temperatures when the pyruvate group is charged, destabilising the polymer chains. Increasing salt content increases the transition temperature by reducing the effective charge on the pyruvate. A simple equivalent mass action model predicts how transition temperatures change as a function of salt concentration. The functional form of the change in transition temperature (1/T) versus natural log (salt concentration) is approximately linear and similar to more traditional polyelectrolyte theories. Transition temperatures in xanthans containing nominally homogeneous pyruvate contents show biphasic transitions, this is because the phases contain different pyruvate levels, however the transitions approach one another in temperature and eventually merge as salt content is increased. It is proposed that pyruvate groups, despite being present at a lower concentration relative to glucuronic acid, dominate the charge interactions due to their location on the outside of the helices.
Original languageEnglish
Article number105184
JournalFood Hydrocolloids
Volume97
Early online date25 Jun 2019
DOIs
Publication statusPublished - 1 Dec 2019

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