The effect of particles on static crystallisation in suspensions: sucrose vs inulin

Abstract

The crystallisation of lipids in suspensions is influenced by the presence of the suspended material, in contrast to crystallisation in bulk lipids. In this research, the impact of carbohydrate particles on the crystallisation of palm oil was studied. Refined crystalline sucrose and glassy inulin were chosen as particulate materials added at a 10 wt% concentration. Suspensions were studied either without additives or together with sucrose ester (HLB 6) at a 0.5% concentration as dispersing agent. Suspensions were crystallized while cooling at 20 °C/min to 20 °C or 25 °C under static conditions. A multiscale analysis of the fat crystal network was conducted where simultaneous wide- and small-angle X-ray scattering were used to study the polymorphism, chain length stacking and crystal nanoplatelet (CNP) thickness. Ultra-small-angle X-ray scattering and cryo-scanning electron microscopy provided insights in the CNP size and shape. Polarized light microscopy and Raman spectroscopy revealed the microscale structure of the fat crystal network. Results show that both crystalline and amorphous particles act as surfaces for heterogeneous nucleation, facilitating nucleation. Polymorphic pathways and lamellar spacings remained unchanged, while CNP size decreased compared to crystallisation in the bulk lipids. The effects of the particle nature were subordinate to those of the dispersing agent.