High sugar content impacts microstructure, mechanics and release of calcium-alginate gels

Artikel i vetenskaplig tidskrift, 2018

The use of calcium-alginate gels as carriers of food and pharmaceutical compounds is of great interest due the versatile properties of such systems. In this work, we investigated the influence of sugars (glucose: fructose) as cosolutes (15-60% (wt)) on the physico-chemical properties of calcium-alginate gel particles. Sugar concentrations above 15% (wt) reduced extensibility of alginate molecules, as shown by intrinsic viscosity measurements, and lead to a more open or less connected gel network with aggregated alginate strands. Furthermore, it is shown for the first time that sugar impacted swelling-deswelling ability of calcium alginate gels under simulated gastric (pH 1.2) and intestinal (pH 6.6) conditions. Release of sugar from calcium alginate gels with 15% (wt) and 30% (wt) sugar was close to Fickian diffusion mechanism, in both simulated gastric and intestinal fluid, with diffusion coefficient close to that previously reported for calcium-alginate gels with lower sugar contents. However, release from 60% (wt) gels in gastric fluid was slower than for 15 and 30% (wt) and, there was a drastic shrinkage of the gels under acid conditions. In intestinal fluid 60% (wt) gels showed slower release than gels with lower sugar content, this was hypothesised to be due to the lower surface area of these gels. Understanding the structure-function relationship of these gels is key to the successful design of delivery systems for food and biotechnological applications.