Impact of purification and fractionation process on the chemical structure and physical properties of locust bean gum

Crude locust bean gum (CLBG) was purified and fractionated into two parts: the first was obtained by solubilization in water at 25 °C (GM25) and the second consisted in a further extraction at 80 °C on the residual impoverished fraction (GM80). The complete structural characterization has shown that GM80 possessed relatively longer chain lengths than GM25, a slightly lower degree of galactose substitution and a somewhat sharper galactosyl distribution in substituted and unsubstituted regions. A physical behavior analysis was carried out on solubilization kinetics, viscosity, viscoelasticity and formation of associated gels with xanthan or carrageenan. The average structure of GM80 generated larger intra-chain, inter-chain and inter-molecular interactions, resulting in the appearance of a stronger network. Small structural differences therefore generated very different physical behaviors. This study thus allowed to establish, in a precise and complete manner, fractionation–purification–structure–function relationships of galactomannans extracted from carob.