No abstract

Saturated fats are widely present as components in fat-rich products because of their structuring and organoleptic properties. Nevertheless, their intake needs to be limited from a nutritional perspective. Therefore, alternative approaches for oil structuring are necessary to produce a solid-like fat with a reduced saturated fat content. However, these products often show instability upon storage. Therefore, this project evaluated the microstructure development in semi-liquid shortenings (6% hardstock in rapeseed oil) upon storage. The shortenings, produced at an industrial pilot plant, were stored at 5, 15 and 20 °C and evaluated from nano- tot macroscale with DSC, rheology, oil binding capacity test, PLM, (U)SAXS and WAXS during storage. Concerning the hardstock types, two of them originated from fully hydrogenated palm oil and two from fully hydrogenated rapeseed oil. In each group, one hardstock mainly contained TAG and one mainly MAG. The aim of my project was to investigate the microstructure development in shortenings and relate this to their stability and their resistance to shear. As function of the storage time, the major changes could be established for the rheological parameters |G*|, d and ty. Regarding storage temperature, the behavior of the TAG-based shortenings was more temperature-dependent compared to MAG-based shortenings. Storage at 5 °C resulted in less rigid shortenings compared to 15 and 20 °C. The most rigid shortenings were those containing mainly MAG derived from palm oil (|G*| ± 104 Pa). The highest recovery (> 65%) and oil binding capacity (oil release < 0.2%) were found for the shortening based on TAG from rapeseed oil when stored at 15 and 20 °C. The crystallite thickness distribution obtained with SAXS could be linked to the quality (rigidity, oil binding capacity) of the shortenings. The USAXS results were in line with other parameters, but further validation is required regarding CNP size and cluster dimensions.

Fat suspensions, i.e. heterogenous mixtures of solid particles in a fat, are omnipresent in food products. Depending on the temperature, the lipid phase consists of a liquid and a solid fraction, often expressed as solid fat content (SFC). In suspensions, the solid particles also tend to affect the SFC, which makes it an important parameter to study. Conventionally, for plain fats, the SFC is acquired via an NMR measurement (AOCS Cd16b-93). Complex mixtures, like suspensions, are more difficult to study by NMR, as the solid particles produce an interferent signal. This can be overcome by using a specific standard and an adapted method (AOCS Cd16-81). As an alternative, the use of small-angle X-ray scattering (SAXS) for determining the SFC was studied. The aim of this study was to develop a methodology for determining the SFC in plain fats, but also in complex mixtures, without the need for extra standards or calibration. Moreover, SAXS has proven to be a suitable technique as there is no (or a constant) contribution of solid particles to the signal obtained from the fat. The SAXS equipment used is a Xenocs Xeuss 3.0 equipped with a Cu-source and moveable detector. Plain palm oil and palm oil-sucrose mixtures were studied at several isothermal crystallization temperatures. The SAXS technique allows to follow the SFC continuously over time during isothermal crystallization, which is not possible with NMR. From a SAXS profile, the liquid and solid fat contribution can be clearly separated. The separation of the solid and liquid contribution and their respective quantification was optimized. Special interest was put into the contribution of different triacylglycerol polymorphs. For plain fats, the results were compared to conventional results obtained with NMR and were found to be very similar. For suspensions, the results were verified with other techniques, such as DSC.

Oleogelation offers the possibility to reduce the saturated fatty acid (SAFA) content while maintaining the desired organoleptic properties. Hereby, SAFAs are replaced by other structurants which can create a three‐dimensional network that immobilizes the liquid oil. Depending on the type of structurants, different structuring routes are identified. The use of monoacylglycerols (MAGs) as structurants is a promising approach thanks to their great self‐assembling properties. However, implementation into the food industry is still hampered due to insufficient characterization. This research includes a multiscale analysis of two dynamically produced MAG‐based oleogels (6% MAGs in oil, MO1 and MO2) as a function of the storage time (up to 8 weeks). Slight differences in the production process resulted in pronounced differences in techno‐functional properties of the MAG‐based oleogels. MO1 consisted of larger crystals, which resulted in a lower rigidity, reduced stability, and lower oil binding capacity compared with the other oleogel (MO2). On the nanoscale, it was found that the crystal nanoplatelets (CNPs) of MO1 contained a higher number of lamellae compared with MO2. Additionally, the results obtained with ultra‐small angle x‐ray scattering indicated a larger equivalent diameter for the CNPs of MO1. As a function of the storage time, both oleogels did not show major structural changes up to 8 weeks of storage.

Oleogelation offers the possibility to reduce the saturated fatty acid (SAFA) content while maintaining the desired organoleptic properties. Hereby, SAFA are replaced by other structurants which can create a three-dimensional network that immobilizes the liquid oil. Depending on the type of structurants, different structuring routes are identified. The use of monoglycerides (MAGs) as structurants is a promising approach thanks to their great self-assembling properties. However, implementation into the food industry is still hampered due to insufficient characterization. This research includes a multiscale analysis of two dynamically produced MAG-based oleogels as a function of the storage time (up to 8 weeks). Slight differences in the production process resulted in differences in techno-functional properties between the MAG-based oleogels MO1 and MO2. MO1 consisted of larger crystals, which resulted in a lower rigidity, lower stability and lower oil binding capacity compared to the other oleogel (MO2). On the nanoscale, it was found that the crystal nanoplatelets (CNPs) of MO1 contained a higher number of lamellae compared to the MO2. Additionally, the results obtained with ultra-small angle X-ray scattering indicated a larger equivalent diameter for the CNPs of MO1. As a function of the storage time, both oleogels did not show major structural changes up to 8 weeks of storage.