Yield Stress Dependent Foaming of Edible Crystal-Melt Suspensions

Crystal-melt suspensions (CMSs) are yield stress shear thinning fluids in which crystal network formation is responsible for the appearance of a yield stress. This study investigates the influence of crystal concentration and morphology on the yield stress of CMSs made from palm kernel oil (PKO) and aims to understand gas bubble stabilization in such systems. Crystallization in laminar flow depends on shear; thus, different shear rates were applied to produce PKO CMSs. With increasing shear rate, a higher yield stress at a constant crystal content was found. This behavior is expected to originate from the increased aspect ratio and/or smaller size of crystals or crystal agglomerates formed at higher shear rates. The related influence of crystal network formation on gas bubble stabilization was investigated. Normalized bubble diameters of PKO CMS foams were shown to decrease for an increasing Bingham number approaching a value of 1. We demonstrate hereby that gas bubbles are best stabilized within fat melts by crystal network formation resulting in stable fat microfoams with an adjustable structure–rheology relationship through tailored crystallization and low dissipation membrane microfoaming.