Dispersed, optical and concentration characteristics of submicron heterogeneities in aqueous solutions of sugars

[Display omitted] •Submicron heterogeneities spontaneously form in aqueous solutions of sugars.•A method for determining the refractive index of low-contrast particles in solutions.•Submicron heterogeneities are stable regions with altered sugar concentrations. In this work, a multilateral analysis of submicron heterogeneities (SMH) spontaneously formed in aqueous solutions of sugars - glucose, fructose and sucrose - was carried out at 25 °C using laser scattering methods. The hydrodynamic diameters of SMH in 0.5 mol% solutions are 100–150 nm and vary slightly over a wide range of concentrations. However, the geometric diameters of SMH turn out to be much larger – 150–250 nm. This observation assumes that SMH are rather loose objects. The absence of depolarization of scattered radiation shows that the shape of MH is close to spherical. A new approach based on the methods of dynamic and multi-angle static light scattering using the Mie theory has been developed, which allows determining the refractive index of SMH. In 0.5 mol% solutions of sugars, the refractive index of SMH differs from the surrounding solution by no more than 0.005 for glucose and fructose and no more than 0.01 for sucrose. This corresponds to a 1.8-fold higher concentration of sugars in SMH compared to the average concentration in solution. Although SMH in sugar solutions are practically invisible due to the very small contrast, their numerical concentration is quite large, ∼1011–1012 ml−1, and they occupy a ∼0.1–1 % volume fraction of the solution. Dispersed and optical characteristics of SMH depend on the type and concentration of sugar.