Locust Bean Gum

One of the vegetable gums that has received much attention in froth flotation is locust bean gum (LBG). LBG, as a vegetable-originated chemical, can be produced in the extraction process from the carob plant’s seed (Ceratonia siliqua), a flowering evergreen tree. It comprises hydrocolloidal polysaccharides (with high molecular mass) composed of galactose and mannose units linked together by glycosidic connections (Fig. 5.1) and is chemically known as galactomannan. As a commercially available water-soluble polysaccharide, LBG can form a solution with high viscosity from slightly acidic to neutral pH (pH: 5.4–7) when dissolved in hot water (around 85 °C). This solution turns into a gel when sodium tetraborate is added. The solution viscosity remains unchanged even when the pH varies from 3.5 to 9.0. Additionally, divalent cations such as Mg2+ and Ca2+ do not affect the viscosity. However, adding an acidic solution or an oxidation agent leads to the formation of LBG salt and, therefore, decreases the viscosity. Various applications are possible for LBG, including gelling, thickening, emulsifying, and stabilizing agents.