Physico-Chemical Properties of Sugar and Polyol Dispersions

Sucrose Crystals in Fondant: Only crystals smaller than approx. 25 µm will not be detected as particles by the human tongue, leading to a silky texture. Bright field (left) and polarized light (right) microscopy of two semi-coarse samples, 40x magnification.

Sucrose Crystals in Fondant: Only crystals smaller than approx. 25 µm will not be detected as particles by the human tongue, leading to a silky texture. Bright field (left) and polarized light (right) microscopy of two semi-coarse samples, 40x magnification.

Apart from sweeting foods, sugar (sucrose) defines physical properties such as viscosity and moisture as well as textural perceptions such as crunchiness in well-defined preparations. Due to its pronounced water binding capacities, sucrose extents the stability and shelf life of products considerably. These empirically observed and useful properties rely in many cases on complex time- and temperature-dependent – and thus non-equilibrium – processes. While substantial technological experience exists in food technology, engineering, and production, a thorough physical understanding of the links between thermodynamic, kinetic and molecular interactions in sucrose-based foods does not exist. Detailed investigations by rheological experiments, combined with microscopic and X-ray observations of highly concentrated sucrose dispersions provide a more in-depth understanding of the multiscale physical properties spanning molecular to macroscopic length and time scales.
Polyols, for example xylitol, erythritol, or isomalt, are gaining in popularity as sugar substitutes. Due to their different molecular structure, however, these sugar alcohols display different crystallization kinetics and dissolution properties. For example, erythritol crystallizes rapidly whereas isomalt can easily be kept amorphous after melting and cooling. A combination of in-depth understanding of the physico-chemical properties of highly concentrated sugar as well as polyol solutions can thus help to gain knowledge about how to substitute sugar in systems whose viscoelastic qualities highly depend on the solubility and crystallization of the bulk material. For this research, rheology as well as microscopy, laser-diffraction and calorimetric techniques are mainly used, and a close exchange with the project on factors influencing erythritol crystallization is fostered.