Tribological properties of neutral polysaccharide solutions under simulated oral conditions.

Predictability of the perception of foods thickened by polysaccharides is only poor. Therefore, the effect of saliva on the lubrication properties of 2 types of neutral polysaccharides, cross-linked starch and locust bean gum, was studied. Despite the similar bulk rheological behavior of the 2 polysaccharides, the starch solution exhibited a significantly lower friction coefficient. Although starch viscosity was strongly decreased upon 10 s incubation with human saliva, a low friction coefficient was retained. The presence of remaining granules is held partly responsible for this. Addition of starch granules to locust bean gum also resulted in a decrease in the friction coefficient, but the effect was smaller compared to starch solutions digested by saliva. Smaller contact angles were measured for (digested) starch compared to locust bean gum solutions. This points to other parameters that assist in lubrication, such as the interaction of starch solution constituents with the rubbing surfaces. In addition, the importance of bulk viscosity for spreadability on surfaces was demonstrated. This study illustrates that the type of starch will determine not only the viscosity change but also the presence of intact granules upon digestion by saliva in the oral cavity; the combination of these 2 properties is regarded to be responsible for the poor predictability of sensory responses of starch containing foods.