Microstructure development in semi-liquid shortenings upon storage

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.

Insights in the Structural Hierarchy of Statically Crystallized Palm Oil

“…The average trends seen by the BWA method are thus similar to those found by the Scherrer equation. The number found by the BWA method is smaller, as found by den Adel et al (2018) and Rondou et al (2022) [2,24]. After one hour of isothermal crystallization, around 60% of the CNPs consist of 3-10 lamellae and about 40% of 11-20 lamellae.…”

“…Thirdly, the Bertaut-Warren-Averbach method (BWA) was applied to obtain the CNP thickness distribution by taking into account the full SAXS peak shape as described in den Adel et al (2018) [24]. The method of Rondou et al (2022) was optimized by fitting the SAXS peak with a Gaussian of multiple terms [2]. Within the range of −0.5 < s* < 0.5, 15 equally spaced peaks were used.…”

“…A certain amount of solid fat and the presence of a fat crystal network are often necessary to create a food product that is technologically, sensorially, and nutritionally functional. In order to control the macroscopic fat properties, a thorough understanding of the distinct structural levels of the fat crystal network (nanoscale: 0.1 nm-100 nm; mesoscale: 100 nm-1 µm; microscale: 1 µm-200 µm; macroscale: >200 µm) is a prerequisite [2].…”

“…Nikolaeva et al (2018) applied USAXS to study the network formation of micronized fat samples [19]. Rondou et al (2022) applied USAXS to study the stability of monoglyceride oleogels [2]. So far, focus has been put on the mesoscale of stable crystallized fats and finished food products and not on the relation between processing conditions and the development and evolution of the mesoscale and the full-fat crystal network during crystallization.…”

From Nucleation to Fat Crystal Network: Effects of Stearic–Palmitic Sucrose Ester on Static Crystallization of Palm Oil

“…The goal was not to obtain an absolute strain value, but to investigate the strain differences with and without the SE. • The CNP thickness distribution was derived by means of the Bertaut-Warren-Averbach method (BWA) as described by den Adel et al (2018) [33] and Rondou et al (2022) [34].…”