Using capillary bridges to tune stability and flow behavior of food suspensions

Abstract

Adding a small amount of an immiscible fluid to a particle suspension can lead to particle bridging and network formation. This effect occurs both if the secondary fluid wets the particles better or worse than the bulk fluid. The capillary bridging phenomenon can be used to stabilize particle suspensions and precisely tune their rheological properties. This allows stable food products to be created as shown here for starch and cocoa model suspensions. Adding small fractions of water to suspensions of starch or cocoa particles in oil increases the yield stress by several orders of magnitude. The yield stress and viscosity can be tuned in a wide range by changing the fraction of the secondary liquid or the wetting properties of the ternary particle/fluid/fluid system. The presence of aqueous capillary bridges between cocoa particles improves the heat stability of model chocolate systems. In suspensions of starch granules that have been conditioned over water, the network induced by capillary bridges forms spontaneously and results in the same yield stress as when the water is added to the suspension of dry particles. This demonstrates, that in contrast to Pickering emulsions, the formation of capillary suspensions is an energetically driven phenomenon. Water continuous suspensions can potentially be used to design novel low fat food products. We have modified suspensions of cocoa particles in water with trace amounts of appropriate oil to achieve texture and flow properties of regular fat continuous cocoa spreads.