Influence of galactomannan on the structure and thermal behaviour of xanthan/galactomannan mixtures

Mixed gels of xanthan gum and galactomannans (guar, whole and fractionated locust bean gum — LBG) were compared by means of oscillatory shear measurements. Whatever the LBG fraction, a synergistic maximum was observed when the ratio of xanthan to galactomannan was 1:1. However, the magnitude of this maximum varied with the LBG fraction used. The thermal behaviour of 1:1 xanthan/LBF fractions was characterized by cooling-heating cycles. A slight thermal hysteresis was systematically described for the several xanthan/LBG fraction systems. It was observed that the mannose to galactose (M/G) ratio of LBG fractions determined the sol-gel transition (gelation and melting temperature) of the xanthan/galactomannan mixed systems. From the galactomannan fine structure and thermorheological profiles it is evident that the higher the M/G ratio of galactomannan samples, the higher is the synergistic interaction as is also the transition temperature of the xanthan/LBG systems