The seed structure of the carob bean tree and guar plant, from the outside to the interior, is shown below:

• the hull,
• the albumen or endosperm which is light cream in color. It is made up of two hemispherical segments (splits) which surround the germ. Its major constituent is the polysaccharide and
• the germ (embryo), which is rich in protein.

Locust bean gum is a polysaccharide that is composed of two sugar molecules: galactose and mannose.

The main chain consists of (1-4) linked beta-D mannose residues and the side chain of (1-6) linked alpha-D galactose. Guar gum has an overall ratio of mannose to galactose of about 2:1, while it is 4:1 for locust bean gum.

1 galactose unit for 4 mannose residues

Studies using partial hydrolysis and Carbon C¹³ NMR have demonstrated that these compositions are only averages. In reality, the galactose sugars are not evenly distributed along the chain, but tend to be clustered together in blocks. This is especially true for locust bean gum. The chains have an irregular structure with alternating "smooth" and substituted zones.  

The ratio of galactose to mannose and their distribution has a significant effect on the physical properties. The galactose substituents are regularly distributed along the mannose chain. Guar gum can be quickly differentiated from locust bean gum using infrared spectroscopy.  In locust bean gum, the ratio of mannose to galactose is higher than in guar gum, giving it slightly different properties, and allowing the two gums (LBG combined with either carrageenan or xanthan gum) to interact synergistically to make a thicker gel than either one alone.  Locust bean gum dissolves when heated up to 80°C - 90°C. Time and mechanical treatment play a role as well. Used alone, it is a thickener. Viscosity at 1% ranges from 2000 cps to 3500 cps.  In the presence of kappa carrageenan and/or xanthan gum, locust bean gum is able to form a gel. There is a particular synergy with kappa carrageenan, leading to:

• Reinforcement of the carrageenan gels
• Elastic texture
• Prevention of syneresis

Structure of a gel combining Kappa Carrageenan + Locust bean gum

Unlike locust bean gum, guar gum is cold soluble, as the molecules contain less mannose and have fewer smooth zones. Both can be introduced into the formulation in solution or sometimes directly dispersed in the medium where heat treatment will achieve proper dissolution. They are both insoluble in media where the total soluble substance is higher than 50%.

Both polysaccharides form viscous, shear-thinning solutions. The viscosities of solutions of the two gums are similar but the range of viscosity is slightly greater for guar gum due to its molecular weight. In terms of properties, guar gum produces a longer texture while locust bean gum has a more pasty and sticky texture. The viscosity increases with concentration. For a given concentration, the viscosity and shear-thinning behavior increase with molecular weight.

The viscosity decreases significantly as the temperature rises. This phenomenon is reversible. Guar gum is more sensitive to acid combined with severe heat treatment, resulting in viscosity loss.