Optical and Thermal Characterization of Locust Bean Gum Using Photopyroelectric Techniques

Galactomannans, like locust bean gum, are polysaccharides widely used in the food and pharmaceutical industries because of their rheological and functional properties. However, their optical and thermal characterization is challenging due to their viscous and highly dispersive nature, which hinders the applicability of conventional spectroscopic and calorimetric techniques. In this study, photopyroelectric techniques were used to simultaneously determine, for the first time, the optical absorption coefficients and thermal diffusivity of locust bean gum in aqueous suspension at various concentrations. Optical characterization was performed at 660 nm (visible) and 1550 nm (near-infrared), revealing strong absorption at 1550 nm associated with hydroxyl group overtones and allowing reliable quantification at concentrations as low as 0.5 g/100 mL. Thermal characterization yielded diffusivity values ranging from 1.50 × 10−3 to 1.47 × 10−3 cm2/s, with a slight decreasing trend as concentration increased. These results confirm the applicability of photopyroelectric methods for the dual optical and thermal characterization of galactomannans and highlight their potential for analyzing complex biopolymer suspensions where traditional methods fall short.