Complex modulus (G*) at 1 Hz, for Gelose 50, Gelose 80, MAZACA, and Melojel as a function of time for storage starch pastes stored at 4°C.

<p>Black: Non-treated control sample, Olive: Pressure releasing rate: 50 MPa/min, Magenta: Pressure releasing rate: 100 MPa/min, Blue: Pressure releasing rate: 900 MPa/min.</p

Chemical composition (w/w, %) of the maize starches used.

<p>Chemical composition (w/w, %) of the maize starches used.</p

Storage modulus <i>G’</i> (solid symbols) and loss modulus <i>G”</i> (open symbols) as a function of frequency.

<p>Symbols are Gelose 80 starch after HHP treatment (pressure releasing rate 100MPa/min) for 0 day storage (blue) and 30 days storage (red).</p

Retrogradation monitored using the FTIR absorbance ratio 1045:1022 cm^-1 for Gelose 50, Gelose 80, MAZACA, and Melojel.

<p>Black: Non-treated control sample, Olive: Pressure releasing rate: 50 MPa/min, Magenta: Pressure releasing rate: 100 MPa/min, Blue: Pressure releasing rate: 900 MPa/min.</p

The original and deconvoluted FTIR spectrum of maize starch Gelose 80 after 0 and 30 days storage after HHP treatment (pressure releasing rate: 100MPa/min).

<p>The original and deconvoluted FTIR spectrum of maize starch Gelose 80 after 0 and 30 days storage after HHP treatment (pressure releasing rate: 100MPa/min).</p

Relationship between the normalized G* (relative to the plateau value) and the normalized FTIR intensity ratio (1045: 1022 cm^-1) for all maize starches during retrogradation.

<p>Relationship between the normalized G* (relative to the plateau value) and the normalized FTIR intensity ratio (1045: 1022 cm^-1) for all maize starches during retrogradation.</p

Zooming in: Structural Investigations of Rheologically Characterized Hydrogen-Bonded Low-Methoxyl Pectin Networks

Self-assembled hydrogen-bonded networks of the polysaccharide pectin, a mechanically functional component of plant cell walls, have been of recent interest as biomimetic exemplars of physical gels, and the microrheological and strain-stiffening behaviors have been previously investigated. Despite this detailed rheological characterization of preformed gels, little is known about the fundamental arrangement of the polymers into cross-linking junction zones, the size of these bonded regions, and the resultant network architecture in these hydrogen-bonded materials, especially in contrast to the plethora of such information available for their well-known calcium-assembled counterparts. In this work, in concert with pertinent rheological measurements, an in-depth structural study of the hydrogen-bond-mediated gelation of pectins is provided. Gels were realized by using glucona-delta-lactone to decrease the pH of solutions of pectic polymers that had a (blockwise) low degree of methylesterification. Small-angle X-ray scattering and transmission electron microscopy were utilized to access structural information on length scales on the order of nanometers to hundreds of nanometers, while complementary mechanical properties were measured predominantly using small amplitude oscillatory shear rheology