Influence of locust bean gum on the rheological behaviour and microstructure of K-kappa-carrageenan

Mixtures of kappa-carrageenan-locust bean gum (LEG) were analysed by transmission electron microscopy and dynamic viscoelastic measurements. The effect of two different mannose:galactose (M:G) ratios of LEG on the rheology and microstructure of kappa-carrageenan in KCl was studied. The rheological differences observed in the mixed gel as LBGs were added were found to be dependent on M:G ratio, salt concentration and LEG content. Monolayers of dilute samples of kappa-carrageenan mixed with LBGs in varying ratios in 0.10 M KCl were visualised by low-angle rotary metal shadowing for transmission electron microscopy. The results obtained showed that LEG hindered the self-association of kappa-carrageenan, and that the effect was enhanced at a higher M:G ratio and as the LEG contents were increased. Small deformation viscoelastic measurements were performed on kappa-carrageenan-LBG mixtures in 0.050 and 0.10 M KCI at constant temperatures of 38 and 48 degrees C, respectively. Increased rheological stability was observed for mixtures containing a relatively high LEG content. Mixtures with a relatively low LEG content showed a maximum in storage modulus and an increase in phase angle. The stabilising effect of LEG on the theology of the blends was more effective for the LEG with high M:G and as the LEG content was increased.