Unexpected phase behavior of amylose in a high solids environment

Area of Science:

• Food science
• Polymer science
• Materials science

Background:

• Amylose is a key component of starch with unique structural properties.
• Understanding amylose behavior in complex mixtures is crucial for food processing and material development.
• Industrial polysaccharides often exhibit coil-to-helix transitions and influence vitrification kinetics.

Purpose of the Study:

• To investigate the structural behavior of amylose in glucose syrup mixtures.
• To compare amylose's phase transitions with those of industrial polysaccharides.
• To elucidate the mixing and phase separation phenomena in amylose/glucose syrup/water systems.

Main Methods:

• Small-deformation dynamic oscillation on shear.
• Modulated differential scanning calorimetry (MDSC).
• Scanning electron microscopy (SEM).
• Mechanistic modeling (free volume/reaction rate theories).

Main Results:

• Amylose retains structural characteristics at low to intermediate glucose syrup levels.
• Phase inversion occurs at >70% solids, forming a cosolute-dominated system.
• Two distinct glass transition temperatures (Tg) were identified, indicating micro phase separation.
• Thermorheological simplicity breaks down, evidenced by two tan delta peaks.

Conclusions:

• The amylose/glucose syrup/water system does not achieve molecular mixing.
• Morphological analysis indicates a micro phase-separated material.
• Amylose exhibits distinct structural behavior compared to typical industrial polysaccharides in concentrated solutions.