The complex mechanism of HM pectin self-assembly: A rheological investigation

• HM pectin gelation is studied through time-resolved mechanical spectroscopy.
• The sol-gel transition is described by time evolution of the mechanical spectrum.
• Viscoelastic models offer suitable guidelines for analyzing the gelation kinetics.
• A generalized plot is suggested for the time evolution of the equilibrium modulus.
• The critical gel time is individuated from data fitting with linear viscoelastic models.

Several biopolymers are widely employed in food, pharmaceutical and biomedical sectors by virtue of their ability to generate supramolecular structures, typically physical hydrogels. In the case of high methoxyl pectins (HMP) the gel formation is promoted by the presence of cosolutes (sugars or polyols) and low pH. The present investigation regards the structuring kinetics of aqueous HMP solutions having different polymer concentration and equal sucrose content at 20 °C. A sequence of consecutive frequency sweep was applied to each sample immediately after its preparation. The time evolution of the linear viscoelastic behavior is described by the sigmoidal profiles of both moduli at each applied frequency and more thoroughly defined through the change of the mechanical spectrum, i.e. the variation of the parameters of the generalized Maxwell model or the Friedrich–Braun model which are both suitable to provide a satisfactory data fitting.