Impact of sucrose and trehalose on different agarose-hydrocolloid systems

• Impact of sucrose/trehalose on thermo-mechanical properties of hydrocolloids.
• Sugar affects macroscopic scale by local interaction with water or hydrocolloids.
• Trehalose forms bigger hydrate shells and has a stronger influence.
• Gelling point shifted to higher temperatures by addition of disaccharides.
• Water holding capacity is influenced at long and short time scales.

Adding high amounts of sugar influences the physical properties of hydrocolloid systems enormously, due to their mutual interactions with each other as well as with water molecules. The impact of the two disaccharides sucrose and trehalose on the thermo-mechanical properties of agarose based hydrogels is investigated. Agarose, a typical gelling agent, is combined with the nongelling agents sodium-alginate and xanthan, two polyelectrolytes which differ significantly in their flexibility. Material properties, such as viscoelasticity, water holding capacity, gelling temperature and thermal stability can be adapted by the controlled addition of sugar. These properties are investigated by strain and temperature dependent oscillatory rheological measurements as well as by controlled drying experiments. The experiments clearly indicate the competition of the different carbohydrates for water. The differences in water binding of sucrose and trehalose are clearly visible. A phenomenological model is presented and illustrates the different effects of the sugar molecules on the hydrocolloid systems. It is suggested that hydrate shells and the differences in local water binding on atomistic and nano scales have strong effects on macroscopic properties.

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