XANTHAN LOCUST BEAN GUM INTERACTIONS AND GELATION

The gelation of xanthan-locust bean gum (LBG) mixtures has been investigated. It has been observed that, over the ionic strength range chosen, the melting temperatures of the gels (T(g)) remains constant, whereas the order-disorder transition temperature (T(m)) for xanthan alone increases with increasing ionic strength. The preparation temperature (T(p)) of the mixed gels is known to affect gelation. Studies have been made on the effect of T(p) relative to T(g) and T(m) on gelation. It has been observed that gelation occurs at all T(p), even when T(p) < T(m). At a given ionic strength, increasing T(p) leads to an increase in the measured storage modulus (G') which closely follows the degree of disordering of the xanthan molecules. Similarly, for a fixed T(p), increasing the ionic strength stabilises the ordered xanthan conformation and is found to reduce the measured storage modulus (G'). These results are discussed in the light of the current models for mixed-biopolymer gelation.