Effect of sucrose on agarose gels mechanical behaviour

The use of sucrose solutions as a binary solvent for the agarose biopolymer is investigated over a broad range of concentration. Three different molecular weight agarose samples have been studied in different sucrose/water ratios using small and large deformation mechanical measurements, DSC measurements, turbidity measurements and TEM microscopy. It is shown that the addition of sucrose results in a less heterogeneous gel network though the aggregation of helices into fibres is still present. The small deformation oscillatory measurements indicate that addition of sucrose induces a modification of the kinetics of gelation, i.e. a modification of the apparent gelation temperature and long-time modulus. Large deformation results indicate that increasing the sucrose/water ratio results in a large increase in the strain at failure, which can extend from 40% to more than 150%. This phenomenon can be explained by melting (under stress) and reforming of cross-links within a more homogeneous physical network (character exhibited by gelatin/water gels). Strain and stress at failure have been fitted empirically using an exponential function whose parameters can be interpreted in terms of agarose molecular weight and concentration. An inflexion point is always found at 20% w/w sucrose concentration when strain and stress at failure and also the Youngʹs modulus are plotted as functions of sucrose concentration at a given agarose concentration. ition it is concluded that the effect of agarose average molecular weight on gelation and gel properties is reduced when sucrose is added.