Determination and quantification of interactions at the molecular scale between polysaccharides in aqueous solution using fluorescence spectroscopy

National audienceNowadays, due to their natural origin, reasonable price and abundancy, a variety of polysaccharides are widely used in many industries such as the food or cosmetics because of their gelling or thickening properties. Among all the polysaccharides available, it is established that some may interact together thus inducing large increasing of viscosity and/or new properties such as gel forming. Such phenomenaare of primary interest from industrial point of view as it brings dramatic increase of macroscopic properties. Nevertheless, such phenomena often remain misunderstood for both the nature and the intensity of the interactions involved at the molecular level.Based on this lack of knowledge, the present work aims (i) to determine the nature and (ii) to measure the intensity of the different types of interactions involved in aqueous solutions containing different polysaccharides by using fluorescence spectroscopy.To this end, xanthan/galactomannan mixtures were chosen due to their well-known synergy when mixed together in aqueous media. Over the past forty years, many researchers investigated this positive synergy at a macroscopic scale; these works resulted in proposing interaction models1,2,3,4 that nowadays still remain controversial.This difficulty is mainly due to a lack of consideration of the fine chemical structure for both polysaccharides, this structure being subject to variability due to a number of parameters such industrial processes, climate, origin, … In our laboratory we have already finely characterized such polysaccharides5,6.Previous fluorescence spectroscopy measurements using specific probes allowed demonstrating the existence of different types of interaction for xanthan/galactomannan mixtures (unpublished results). Now, work is in progress in order to, firstly, identify all the types of interactions and, in a second step, to rank and quantify the intensity of each type of interaction.The final goal is to build a model allowing predicting the macroscopic properties (e.g. rheology) on the basis of the chemical structure of both polysaccharides.It is obvious that such an innovative methodology may be easily generalized to anyother polysaccharide/polysaccharide mixtures.1 Dea, I. C. M.; Morris, E. R.; Rees, D. A.; Welsh, E. J.; Barnes, H. A.; Price, J. Carbohydr. Res. 1977, 57, 249–272.2 McCleary, B. B. Carbohydr. Res. 1979, 71 (1), 205–230.3 Tako, M.; Nakamura, S. Agric. Biol. Chem. 1984, 48 (12), 2987–2993.4 Cairns, P.; Miles, M. J.; Morris, V. J.; Brownsey, G. J. Carbohydr. Res. 1987, 160, 411–423.5 Tapie, N.; Malhiac, C.; Hucher, N.; Grisel, M. J. Chromatogr. A 2008, 1181 (1–2), 45–50.6 Grisel, M.; Aguni, Y.; Renou, F.; Malhiac, C. Food Hydrocoll. 2015, 51, 449–458