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.

Crystalline glycerides play an important role in the formation of multiphase systems such as emulsions and foams. The stabilization of oil/water interfaces by glyceride crystals has been extensively studied compared to only few studies which have been dedicated to oil/air interfaces. This study investigates the crystallization and network formation of tripalmitin (TP) and monopalmitin (MP) at the middle-chain triglyceride (MCT) oil/ air interface. TP crystals were found to crystallize in the bulk before aggregating as large rectangular crystal conglomerates at the MCT oil/air interface. This leads to the slow formation of a plastic deformable, macroscopic crystal layer with high interfacial rheological moduli. MP crystals form directly at the MCT oil/air interface resulting in a comparatively fast formation of an elastic deformable network. Crystals with tentacle-like morphology were found to be responsible for the network elasticity. In this work, we show how interfacial crystallization dynamics and mechanical strength can be linked to the molecular structure and crystallization behavior of glyceride crystals.

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