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.

Oleaginous yeasts offer a promising sustainable alternative for producing edible lipids, potentially replacing animal and unsustainable plant fats and oils. In this study, we screened 11 oleaginous yeast species for their lipid profiles and identified Apiotrichum brassicae as the most promising candidate due to its versatility across different growth media. A. brassicae grown in a dairy side stream produced lipids with a composition most similar to cocoa butter, but the stearic acid and linoleic acid content varied greatly when grown on different substrates. We visualised the formation of lipid droplets by digital holotomography. Pilot-scale production was followed by enzymatic and ultrasonic treatment of biomass and heptane/ethanol extraction. The fatty acid (FA) and triacylglycerol (TAG) composition, thermal behaviour, and solid fat content of A. brassicae lipids was compared to benchmarks such as beef fat, cocoa butter, palm oil and milk fat. The FA profile of the A. brassicae lipids shares the same types of fatty acids with cocoa butter, beef fat and palm oil, however concentrations differ resulting in a lower content of saturated FAs. This increased the proportion of unsaturated TAGs, reducing the melting and crystallisation temperatures and the solid fat content. The microbial lipids contained the major TAGs of cocoa butter at similar ratios, resulting in a comparable melting peak and crystallisation peaks similar to the low-melting groups of beef fat and palm oil. Fractionation has the potential to produce beef fat, cocoa butter or palm oil equivalents with desired techno-functional properties. This study demonstrates the potential of A. brassicae to produce tailored lipid profiles for various food applications through strain and process engineering or downstream processing.

Cryogel particles were obtained by freeze-drying and grinding hydrogel monoliths made from 20 % (w/w) whey protein isolate (WP) suspensions prepared at different pH (pH 4.8, 5.7, and 7.0). The microstructure, porosity, and density of the cryogels were strongly affected by the starting pH of the suspension. At pH 4.8, corresponding to the isoelectric point, proteins assumed a globular form leading to a cryogel with the highest porosity and lowest density compared to those formed at higher pH values (5.7 and 7.0). Such morphological differences accounted for different oil structuring capabilities. When mixed with oil, the cryogel particles formed at the pI were capable of entrapping larger quantities of oil (∼63 % w/w) than those obtained distant from the pI (∼47 %, w/w), forming a spreadable material. In this system, as confirmed by confocal microscopy, WP particles were evenly distributed in oil forming a network connected by capillary bridges and surface hydrophilic interactions. Thus, the mixture of sunflower oil with cryogel particles formed at the pI allowed to obtain an oleogel, exploitable for fat replacement, as confirmed by the preparation of a cocoa spread prototype. Results highlighted the critical impact of protein hydrogel structure in determining the ability of the cryogel particles thereof to entrap oil and tune the oleogel characteristics. The potentialities of this innovative material as ingredient of low saturated fat food products were also demonstrated.

Fat polymorphism plays a critical role in the structural and functional properties of fat-based food products. However, research on the polymorphism of monoglyceride oleogels remains limited. Previous work demonstrated the impact of composition and processing on the polymorphic transitions of monoglyceride oleogels, indicating that high shear and cooling rates accelerate β-polymorph formation. However, a detailed understanding on the effect of shear is still lacking. This research extends previous observations by using a CSS450 shear cell, allowing for precise control over cooling and shear rates. Two commercially available food-grade monoglycerides were mixed with rapeseed oil (10% w/w). Crystallization was performed with varying shear rates and analyzed with synchrotron radiation X-ray scattering techniques (SAXS and WAXS), differential scanning calorimetry and microscopy. The results showed that applying a low shear rate did not result in changes in the polymorphic transitions compared to static crystallization for both monoglyceride oleogels. However, increasing the shear rate resulted in the formation of the β-polymorph, even before the formation of the metastable sub-α polymorph. These findings provide new insights into the role of shear in monoglyceride oleogels, allowing for further optimization of fat structuring in food applications.