Sucrose release from agar gels: Effects of dissolution order and the network inhomogeneity

The effect of sucrose addition prior to or following the dissolution of agar on sucrose release from 1 wt% agar gels was studied. The order of addition was found to affect the fracture stress, fracture strain and sucrose release ratio. At sucrose concentrations below 30%, the rheology (fracture stress and strain) and structure of the gels did not depend on the order of addition of sucrose and agar. At sucrose concentrations >40%, however, the network structure of gels where sucrose was dissolved before agar addition was weaker than that of gels where sucrose was added after agar dissolution. The weaker network structure resulted in lower fracture stress and strain values. For gels prepared by adding agar to sucrose solutions, both fracture stress and strain decreased with increasing sucrose concentration in the range 40–55%. The decrease in fracture stress and strain led to an increase in the sucrose release ratio. The sucrose release ratio decreased monotonously with increasing concentration of sucrose when agar was dissolved prior to sucrose addition. The findings are discussed in relation to recent publications on gel inhomogeneity.