INFLUENCE OF GALACTOMANNAN ON THE STRUCTURE AND THERMAL-BEHAVIOR OF XANTHAN GALACTOMANNAN MIXTURES

Mixed gels of xanthan gum and galactomannans (guar, whole and fraction ated locust bean gum - LBG) were compared by means of oscillatory shea r measurements. Whatever the LBG fraction, a synergistic maximum was o bserved 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 observ ed that the mannose to galactose (M/G) ratio of LBG fractions determin ed the sol-gel transition (gelation and melting temperature) of the xa nthan/galactomannan mixed systems. From the galactomannan fine structu re and thermorheological profiles it is evident that the higher the M/ G ratio of galactomannan samples, the higher is the synergistic intera ction as is also the transition temperature of the xanthan/LBG systems .