Structure impact of two galactomannan fractions on their viscosity properties in dilute solution, unperturbed state and gel state

Two fractions of carob galactomannans (GM25 and GM80) were extracted at respectively 25 °C and 80 °C from crude locust bean gum. Those fractions having slightly different chemical structures, previously characterized, were studied for their viscosity properties over a wide range of concentrations: diluted solution, unperturbed state and gel state. For each of the physical properties, links to the chemical fine structure could be established, expanding knowledge on the topic: in dilute solution, GM25 is more soluble in water while GM80 seems to tend to self-association due to its structure as highlighted by intrinsic viscosity measurements ([η]GM25 = 9.96 dL g−1 and [η]GM80 = 4.04 dL g−1). In unperturbed state, initial viscosities η0 were more important for GM80 fractions at 1% and 2% due to greater hyperentanglements (η0(GM80,1%) = 9.9 Pas; η0(GM80,2%) = 832.0; Pa.s η0(GM25,1%) = 3.1 Pas; η0(GM25,2%) = 45.1 Pas). In gel state, hydrogels obtained from GM80 were also stronger (hardness GM80 (2%) = 0.51 N and hardness GM25 (2%) = 0.11 N), suggesting a much more important number of junction areas within the gel network. The findings discussed herein demonstrate the potential for new applications.