Molecular characteristics of tara galactomannans: Effect of degradation with hydrogen peroxide

Tara gum (M_w = 1519 × 10³ g/mol) was degraded by hydrogen peroxide in the presence/absence of ascorbic acid, and properties of the products were investigated using gel permeation chromatography, Fourier transform infrared spectroscopy, atomic force microscope, and rheometer methods. Results showed that molecular weight of tara gum decreased with increasing concentration of hydrogen peroxide. The addition of ascorbic acid could sharply increase the degradation rate and degree of tara gum by hydrogen peroxide, which is also confirmed by atomic force microscope. The degradation products kept the structure characteristics of galactomannan. However, they performed different rheological properties. At 1% (w/v) of concentration, DP1 (941 × 10³ g/mol) and DP2 (335 × 10³ g/mol) prepared by H₂O₂ exhibited non-Newtonian behavior, while DP3 (35.1 × 10³ g/mol) and DP4 (14.2 × 10³ g/mol) obtained by hydrogen peroxide plus ascorbic acid displayed Newtonian property. These results may promote the application of tara gum in diverse fields.