Tara gum, locust bean gum (E417) and guar gum (E412) have similar structures that consist of a linear main chain of (1-4)-ß-D-mannopyranose units attached by (1-6) linkages with α-D-galactopyranose units. The molecular weight of these gums is in the order of 106 Dalton.
The galactose residues are distributed non-uniformly along the mannan chain. The presence of galactose side units tends to inhibit aggregation, so those gums with more side chains are easier to dissolve in water. The ratio of mannose to galactose in tara gum is 3:1, in the middle compared to LBG which is 4:1 and guar gum 2:1. Tara gum requires heating to disrupt the aggregates and to achieve complete hydration, whereas guar gum hydrates completely in cold water.
Tara gum shows an intermediate acid stability between LBG and guar gum. Tara gum resists the depolymerisation effect of organic acids to a pH of 3.5. LBG is stable to a pH of 3.0 and guar gum to a pH of 4.0.
The viscosity of a 1% solution of tara gum is around 5,500 cps, similar to guar gum and almost three times higher than LBG.
Tara gum is stable to high temperature heat treatment. It can resist up to 145°C in a continuous process plant or 121°C for 30 minutes in batch sterilisation. These characteristics are similar to the ones shown by LBG and far superior to guar gum.
Tara gum could therefore used as a replacement for locust bean gum and guar gum.