The application of shear-crystallization often plays an important role in the production of fat based products such as shortenings/margarines but has been rarely reported. In this study, three blends of palm oil (PO) with anhydrous milk fat (AMF) (0, 25 and 50% AMF, w/w) were rapidly crystallized under static (using freezer) and shear condition (using scrapped surface heat exchanger). Various techniques including differential scanning calorimetry (DSC), X-ray Diffraction (XRD), polarized light microscopy (PLM), rheology and texture analysis were applied to investigate physicochemical properties of fat blends as well as their crystal morphology upon the long-term storage (4 weeks) at 5°C. The results revealed that shear-crystallization not only affected melting behavior of fat blends but also limited the polymorphic transformation from β’ to β crystals. Besides, the application of shear-crystallization helped improve significantly the storage modulus as well as the firmness of fat based products. Although the post-crystallization of low melting triacylglycerols (TAGs) in AMF occurred for both static and shear-crystallized fat blends during the storage accompanying with the firmness evolution, it affected more considerable crystal morphology of the latter. This phenomenon promoted the sintering between tiny fat crystals of shear-crystallized fat blends resulting in the formation of unwanted large aggregates (or granular crystals) with the size ranging from 100-500μm.
