High acyl gellan gum and low acyl gellan gum are two forms of gellan gum that are commonly used in the food industry as thickening, stabilizing, and gelling agents. While both forms of gellan gum can form gels, there are differences in their thermo-reversible gel formation properties.
High acyl gellan gum is known to form thermo-reversible gels, which can be melted and re-gelled upon heating and cooling, respectively. The gelation process of high acyl gellan gum is primarily driven by the formation of double helical structures between the acyl groups and the gellan gum polymer chains. When the solution is heated above the gelation temperature, the double helices unravel and the gel melts. When the solution is cooled below the gelation temperature, the double helices reform and the gel is reformed. The thermal gelation temperature for high acyl gellan gum is typically around 35-40°C.
In contrast, low acyl gellan gum does not generally form thermo-reversible gels. The gelation process of low acyl gellan gum is primarily driven by the interaction of the polymer chains with divalent cations such as calcium ions. The resulting gels are relatively rigid and brittle and do not typically melt upon heating. Instead, they may undergo syneresis or shrinkage upon heating, and once the gel is broken, it cannot be reformed upon cooling.
In summary, high acyl gellan gum can form thermo-reversible gels, while low acyl gellan gum does not generally form such gels. The choice between the two types of gellan gum depends on the specific application and the desired properties of the final product.
