Texture properties of gellan gels as affected by temperature

Gellan gels can be made very brittle, similar to agar gels, or very flexibl e, like gelatin gels. The entropy or enthalpy nature governing those gellan gel behaviors was studied by mechanical testing at temperatures varying fr om 2 to 62C. Both failure stress and strain for 1 % low acyl and low acyl/h igh acyl mixed gellan gels decreased with increasing temperature, indicatin g that the hydrogen bonding contributed significantly to the stabilization of gellan gels in addition to the polyanion-calcium-polyanion bonding. Hydr ophobic interactions were less important. The initial Young's modulus for t wo mixed high: and low acyl gellan gels containing 2 mM Ca++ increased with temperature from 2-42C, indicating entropy elasticity. Average molecular w eighs between adjacent crosslinks:for these two mixed gels was larger than 10(4). For-other gels, the entropy elasticity was not a dominant mechanism for elastic force because of molecular: weights between crosslinks; and fro m the observation: of negative temperature dependence of the modulus.