Single-phase mixed gels of xyloglucan and gellan

Gelation in mixtures of xyloglucan and gellan was investigated using dynamic rheometry, differential scanning calorimetry (DSC), and atomic force microscopy (AFM). The examined gellan and xyloglucan did not form a gel at concentrations below 0.5% w/w and 0.75% w/w, respectively, while a mixture of 0.05% w/w gellan and 0.7% w/w xyloglucan formed a single-phase gel, demonstrating synergistic interactions between gellan and xyloglucan. The coil-to-helix transition temperature of gellan alone, determined by DSC, increased with increasing gellan concentration. In the case of binary polysaccharide mixtures, the conformational transition temperature of gellan increased with increasing xyloglucan content at a total polysaccharide concentration of 0.75% w/w. AFM images of mixtures diluted from 0.05% w/w gellan and 0.7% w/w xyloglucan revealed network structures of gellan at the micrometer scale. These results suggest that xyloglucan increases the effective concentration of gellan in a mixture, presumably via volume exclusion effects, and thus a network of gellan is formed even at concentrations much lower than the gelation threshold of gellan alone.