Formulation of agar fluid gels in the presence of sugar for confectionery applications

The influence of sucrose was investigated on the formation, microstructure and rheological behaviour of (1.5 wt%) agar fluid gels, with a focus on both the particulate and continuous phases. Rheology, texture analysis and phase contrast microscopy were used to assess the impact of sucrose concentration (0-60 wt%) and the timing of its addition. Increasing sucrose concentration resulted in a reduction of fluid gel particle size, increase in bulk viscosity, and slowed aggregation rate. At high concentrations of sucrose (>45 wt%) present during gelation, a significant increase in the gel particle stiffness and viscoelastic moduli was also observed. In contrast, sucrose addition after gel formation resulted in weakened rheological properties due to a reduction in effective volume fraction of the gel phase. Dilution studies revealed that unbound agar chains in the continuous phase contribute to maintaining interparticle interactions at reduced gel phase volume fractions. However, sucrose diminished the functional role of the continuous phase, likely due to contracted conformation of agar chains in the solution. These results provide insights into the functional relationship between agar and sucrose and offer practical guidance for the formulation of novel fluid gel-based foods where sucrose is a key component.