Specific effect of the linear charge density of the acid polysaccharide on thermal aggregation/ disaggregation processes in complex carrageenan/lysozyme systems

We study thermal aggregation and disaggregation processes in complex carrageenan/lysozyme systems with a different linear charge density of the sulphated polysaccharide. To this end, we determine the temperature dependency of the turbidity and the intensity size distribution functions in complex kappa-carrageenan/lysozyme (kCG/lys) and lambda-carrageenan/lysozyme (lCG/lys) systems. We demonstrate that increasing the temperature up to 80 °C in complex kCG/lys systems results in a monotonous decrease of the turbidity and the average sizes of the complex particles. On the contrary, for lCG/lys systems these values considerably increase with temperature. This suggests that disruption of the intermacromolecular hydrogen bonds at high temperature is mainly responsible for the temperature induced disaggregation in kCG/lys systems, whereas enhancement of the hydrophobic forces in lCG/lys systems at high temperature is responsible for the intensification of its aggregation. SEM images of these systems confirm the strong difference in microstructure. DSC data also show that the temperature induced disaggregation in kCG/lys systems is in disagreement with a decreased thermal stability of lys in the presence of kCG