Experimental studies of freezing fouling of model food fat solutions using a novel spinning disc apparatus

The freezing fouling behavior of a model food fat solution consisting of tripalmitin (PPP) in paraffin oil on 316 stainless-steel surfaces was studied using a novel spinning disc apparatus (SDA). The SDA features all internally cooled, vertical rotating cylinder, which is immersed in the warm test solution. Insulation ensures that deposition occurs only oil the base. Computational fluid dynamics (CFD) simulations of the laminar flow field yielded heat-transfer predictions in good agreement with experimental measurements. The shear stress acting oil the deposit and its surface temperature could therefore be estimated reliably. Studies of freezing fouling at surface temperatures of 2-30 K below the cloud point of solutions of 2-10 wt % PPP showed that the fouling behavior is sensitive to composition, surface temperature, and fluid flow. The deposit consisted of gels of PPP platelets, with solid concentrations much greater than that in the bulk solution. The composition of the deposit varied strongly with formation conditions, particularly flow velocity, indicating that deposition was strongly influenced by factors influencing gelation rather than by heat or mass transfer alone.