Surface properties and emulsification activity of galactomannans

Galactomannans are considered to be predominantly hydrophilic carbohydrate polymers (gums) with a rigid backbone. The gums are not expected to have significant surface activity nor to form primary adsorbed layers on oil—water interfaces. However, it was found that commercial, native LBG and guar gum reduce surface tension of water to ~55 mN/m, and adsorb/precipitate on oil—water interfaces, reducing their interfacial tensions. The surface activity of purified guar, where levels of proteins were reduced to a minimum of 0.8% wt, was not inferior to that of the crude gum, unlike gum arabic. Oil-in-water emulsions of various oils with LBG or guar were prepared. The oil droplets were covered with precipitated gum layers exhibiting strong birefringency, indicating formation of organized gum layers on the interface. The adsorption capacity and surface load have been evaluated. Coalescence and flocculation have been minimized by establishing the best gum/oil ratios for full droplets coverage.