DSC study on properties of water in concentrated agarose gels

The state of water in concentrated agarose gels was studied by differential scanning calorimetry. An endothermic peak was observed at temperatures <0 degrees C in addition to an endothermic peak accompanying the melting of frozen free water at 0 degrees C. The endothermic peak was attributed to the thawing of disordered frozen water, and was found only in concentrated gels whose concentration is >20% w/w. It was found also that there must be some non-freezing water, because the sum of the frozen disordered water and the frozen free water, which was estimated qualitatively from the area enclosed by a DSC peak and a baseline, was less than the total content of water in gels. It was suggested that the disordered frozen water and the non-freezing water exist mainly in junction zones of agarose gels.