Friction properties of oral surface analogs and their interaction with polysaccharide/MCC particle dispersions

Abstract

To optimize food products to better accommodate food product acceptance by end consumers and health or ecological regulations, it is necessary to gain a reliable view of the process that occurs during mastication of products in the oral cavity. The physical description of the mechanical responses due to oral processing is required for a more effective prediction in product (re)formulation. The aim of this work is to derive such an adequate and relevant methodology. For this purpose a tribological and rheological study of polysaccharide solutions was employed using a set of different rubbers that mimic different soft (oral) surfaces and to relate these measurements to material surface properties, as roughness, hydrophobicity and elasticity. The polysaccharides chosen, locust bean gum, pectin and xanthan, represent important components in food products.It is shown that the nature (hardness or roughness) of a surface under good lubrication conditions is not that important. Therefore, in developing new food products it may be of prime importance to control the lubrication properties rather than focus on adaptation to oral surface characteristics, like the consequences of human aging. Xanthan is more effective as lubricant than the negatively charged pectin, while locust bean gum is the worst lubricant that was tested. No clear relation with the apparent contact angle could be made between friction and the aqueous solutions tested.The presence of hard particles on friction is predominantly observed at relatively low entrainment speed (below about 50mm/s) and is most explicitly detectable when lubrication is poor (as for locust bean gum). The MCC particles used in this study may not fit in the surface asperities and thereby enhance surface roughness, which results in extended boundary regime of the Stribeck-curve. Tribology is shown to be useful to detect particles dispersed in a solution, but the better the lubricant the more difficult the detection of such particles will be. Alternatively, this work shows that food products characterized by low friction coefficient can be mixed with elongated particles without large influence on their lubrication properties. This insight might provide openings in reformulation-strategies not only in food but also in pharmacy applications.