In this article, a shape-dependent model for the interpretation of USAXS data is proposed. CNPs are modeled as polydisperse parallelepipeds, and the aggregates are characterized by fractal dimensionality.

Palm oil (PO) is still widely used for the production of all types of food products. Due to its triacylglycerol (TG) composition, PO is semisolid at ambient temperature, offering possibilities for many applications. In order to tailor the fat crystal network for certain applications, it remains imperative to understand the structural build-up of the fat crystal network at the full-length scale and to understand the effect of processing conditions. In this study, PO was crystallized under four temperature protocols (fast (FC) or slow (SC) cooling to 20 °C or 25 °C) and was followed for one hour of isothermal time. A broad toolbox was used to fundamentally unravel the structural build-up of the fat crystal network at different length scales. Wide-angle and small-angle X-ray scattering (WAXS and SAXS) showed transitions from α-2L to β’-2L over time. Despite the presence of the same polymorphic form (β’), chain length structure (2L), and domain size, ultra-small-angle X-ray scattering (USAXS) showed clear differences in the mesoscale. For all samples, the lamellar organization was confirmed. Both cooling speed and isothermal temperature were found to affect the size of the crystal nanoplatelets (CNPs), where the highest cooling speed and lowest isothermal temperature (FC and 20 °C) created the smallest CNPs. The microstructure was visualized with polarized light microscopy (PLM) and cryo-scanning electron microscopy (cryo-SEM), showing clear differences in crystallite size, clustering, and network morphology. Raman spectroscopy was applied to confirm differences in triglyceride distribution in the fat crystal network. This study shows that both cooling rate and isothermal temperature affect the fat crystal network formed, especially at the meso- and microscale.

Palm oil (PO), a semi-solid fat at room temperature, is a popular food ingredient. To steer the fat functionality, sucrose esters (SEs) are often used as food additives. Many SEs exist, varying in their hydrophilic-to-lipophilic balance (HLB), making them suitable for various food and non-food applications. In this study, a stearic–palmitic sucrose ester with a moderate HLB (6) was studied. It was found that the SE exhibited a complex thermal behavior consistent with smectic liquid crystals (type A). Small-angle X-ray scattering revealed that the mono- and poly-esters of the SE have different packings, more specifically, double and single chain-length packing. The polymorphism encountered upon crystallization was repeatable during successive heating and cooling cycles. After studying the pure SE, it was added to palm oil, and the crystallization behavior of the mixture was compared to that of pure palm oil. The crystallization conditions were varied by applying cooling at 20 °C/min (fast) and 1 °C/min (slow) to 0 °C, 20 °C or 25 °C. The samples were followed for one hour of isothermal time. Differential scanning calorimetry (DSC) showed that nucleation and polymorphic transitions were accelerated. Wide-angle X-ray scattering (WAXS) unraveled that the α-to-β′ polymorphic transition remained present upon the addition of the SE. SAXS showed that the addition of the SE at 0.5 wt% did not significantly change the double chain-length packing of palm oil, but it decreased the domain size when cooling in a fast manner. Ultra-small-angle X-ray scattering (USAXS) revealed that the addition of the SE created smaller crystal nanoplatelets (CNPs). The microstructure of the fat crystal network was visualized by means of polarized light microscopy (PLM) and cryo-scanning electron microscopy (cryo-SEM). The addition of the SE created a finer and space-filling network without the visibility of separate floc structures.

Anhydrous milk fat (AMF) is a flavorful, but particularly complex fat containing a wide variety of fatty acids (FAs) and triglycerides (TGs), resulting in an extended melting range of -40 °C to 40 °C. The functionality of this fat can be steered by the addition of sucrose esters (SEs). In this study, the crystallization behavior of AMF in the presence of a stearic-palmitic SE was assessed. Samples were cooled at 1 °C/min (slow cooling) or 20 °C/min (fast cooling) to 0 °C, 20 °C or 25 °C and kept isothermal for one hour. At each of these temperatures, AMF was found to crystallize via different polymorphic pathways and chain length structures, as studied by wide- and small-angle X-ray scattering. The addition of the SE (0.5 wt%) accelerated nucleation and allowed crystallization to start at higher temperatures. Polymorphic transitions were accelerated, but not changed. For fast-cooled samples, ultra-small-angle X-ray scattering provided insights into the mesoscale behavior of the crystal nanoplatelets (CNPs). It was observed that CNPs formed at 20 °C were smaller than those at 25 °C. The addition of the SE did not change the size nor the shape of CNPs. Polarized light microscopy (PLM) and cryo-scanning electron microscopy (cryo-SEM) gave insight into the microstructure of the networks. Addition of the SE resulted in more fine and dense fat crystal networks at 0 °C and 20 °C. At 25 °C, large separate floc structures were encountered, with and without the addition of the SE.

Time-resolved multiscale analysis of triglycerides during crystallization.