From Curdlan Powder to the Triple Helix Gel Structure: An Attenuated Total Reflection—Infrared Study of the Gelation Process

Abstract

Infrared spectroscopy was used to probe the hydration and gelation of curdlan, a linear polysaccharide built from repeating units of (1→3)-β-D-glucose. The spectra have been recorded using a temperature-controlled attenuated total reflection (ATR) device. Thermal gelation of curdlan could therefore be followed in situ and in real time. The transformation of the low-set gel, mainly formed with single helices, into a high-set gel, associated with a triple helix structure, could be directly observed. The relative intensities and positions of characteristic absorption bands in the C–O region (1200–850 cm⁻¹) were found to be representative of the gel structure, as they are believed to be sensitive to the helical conformation of the polymer chains. Infrared (IR) spectroscopy is shown to be a useful tool for rapid and efficient characterization of curdlan gels.