Effect of different molecular characteristics on the lubrication behavior of polysaccharide solutions

Polysaccharides strongly affect the sensorial properties of foods, which is partly related to the lubrication they provide. We investigated the lubrication performance of polysaccharides with different characteristics (i.e. molecular weight, conformation, stiffness, and charge density) to identify the most relevant structural features related to lubrication ability. The effect of viscosity was excluded using isoviscous systems. Conformation resulted to be a key factor in determining lubrication. Rigid rod-like polysaccharides (xanthan) showed higher lubricating capacity and better resistance to changes in pH and ionic strength compared to semi-flexible (pectin and carboxymethyl cellulose) and flexible polysaccharide (guar gum). The friction behavior of flexible polysaccharides was highly dependent on concentration and sliding speed, for which a model including parameters of friction, concentration, and speed was developed. The concentration-dependency of the lubrication was related to the shear-thinning behavior, and possible mechanisms to explain these differences in terms of molecular properties of the polysaccharides are proposed.