The conformational properties of gellan gum hydrogels

Abstract The conformational properties of gellan hydrogels were examined using a range of experimental techniques. DSC analysis reveals progressive development of the water/polysaccharide interaction at temperatures higher than the gel-sol transition temperature (T ∗ ). X-ray and TMA analyses show that maintaining the gel at temperatures higher than T ∗ (annealing) before cooling has a dramatic effect on the gel structure. The gel strength is increased four-fold by annealing at 365 K for 30 min. The integrity of gellan gels is thought to be maintained by junction zones linked by extended helices. From the collated data a junction zone in gellan gel is estimated to be four double helices wide and five repeat sequences long. SOR data reveal an increase in the size of the junction zones proportional to the annealing time. A nematic liquid crystalline structure is observed following annealing. The sol state of gellan gels is shown not to be an isotropic liquid state but that a high order structure is evolved in the sol state. It is proposed that on heating a gellan gel to a temperature higher than T ∗ initially partial denaturation takes place. Aggregation subsequently occurs and the size of the junction zones increases.

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