Oleogels or, more precisely, non-triglyceride structured lipid phases have been researched excessively in the last decade. Yet, no comprehensive knowledge base has emerged, allowing technology elevation from the laboratory bench into the industrial food application. That is partly due to insufficient characterization of the structuring systems studied. Examining a single composition decided upon by arbitrary methods does not stimulate progress in the research and technology area. A framework that gives much better guidance to product applications can easily be derived. For example, the incremental structure contribution concept is advocated as a parameter to compare the potency of structuring systems. These can straightforwardly be determined by combining solubility data and structural measurements in the recommended manner. The current method to determine the oil-binding capacity suffers from reproducibility and relevance. A newly developed method is suggested to overcome these shortcomings. The recommended new characterization of oleogels should contribute to a more comprehensive knowledge base necessary for product innovations.
In this paper, the structuring of liquid oils, also known as oleogelation, is systematically investigated for the first time using a quasi-quaternary mixing system approach. Native waxes with different quantities of wax esters (WE), n-alkanes (hydrocarbons (HC)), fatty acids (FA), and fatty alcohols (FaOH) are applied in mixtures with hydrolyzed waxes to systematically change the composition. Hydrolyzed waxes contain high levels of FA and FaOH. The model systems are investigated on microscopic level (brightfield light microscopy (BFM), cryogenic scanning electron microscopy (cryo-SEM)) as well as on their macroscopic properties (rheology, gel hardness) and calorimetric behavior (differential scanning calorimetry (DSC)). It is found that sunflower wax (SFW)-based gels (12% structurant) become less hard on any admixture. Beeswax (BW)-based gels show significant increases in hardness when 25% and 50% (w/w) hydrolyzate are admixed. This could be related to stepwise crystallization. Further analysis reveals that the dissolution/melting behavior of the wax ester mixtures can be surprisingly well described as ideal solubility of a single pseudocomponent. The approach to unravel the individual contributions of the different species present in waxes is successful and marks a first step to better understand the systematic of wax functionality as oleogelators. Practical Application: The substitution of hardstock fats in structured oil phases is of interest for two reasons. The improved nutritional profile oleogels offer are beneficial for public health while the elimination of palm oil based ingredients appears to be a general public desire. Among the technical solutions for non-TAG oil structuring waxes are very promising. This is primarily due to their availability, prior consumption, potentially low cost for functionality. Currently waxes are technically and scientifically wrongly treated as single components. In order to better utilize the potential of waxes and design future sourcing strategies it is necessary to understand the wax functionality at a compositional/molecular level. This contribution marks the first step into this direction by considering classes of molecules with respect to their contribution to functionality. This understanding is considered as a key for future compositional design.
Current research on wax‐based oleogels indicates wax esters to be the key component in many natural waxes. This necessitates understanding the properties of pure wax esters to unravel the gelling mechanism in wax‐based oleogels. Therefore, available literature data on pure wax esters is summarized and critically reviewed. The detailed analysis of the pre‐existing data on crystallographic (SAXS) and thermal properties, facilitates the interpretation of subsequently performed experiments: Specific wax esters with different carbon numbers and symmetries were studied as such and in oleogels formed in combination with medium chained triglyceride oil at inclusion levels of 10% (w/w). They were characterized regarding their thermal (differential scanning calorimetry [DSC]) and viscoelastic (oscillatory rheology) behavior. It is found that all observations concerning pure wax esters behave systematically, linking molecular makeup, crystal structure, and behavior. The experimental study of oleogels structured by four different binary mixtures of wax esters revealed that substantial chain length differences induce separate crystallization (CN30 + 36 and CN30 + 42). Mixtures of wax esters with only limited chain length difference (≤ 2 carbon atoms) reconfirmed earlier speculations on mixing behavior and crystal structure. Applying mixtures of wax esters only differing in their position of the ester bond (CN36 [14_22] + CN36 [22_14]) indicated ideal mixing behavior in the solid phase of the gels. Surprisingly, the data revealed that additional thermal events occur at specific mixing ratios, predominantly at 1:1 (w/w). Their supposed relation to compound formation certainly needs further confirmation. Rheological analysis confirmed that sequential crystallization results in highest firmness values for the systems studied.
The non-triglyceride structuring of liquid oils, so-called oleogelation, enables new and more beneficial product designs. Natural waxes have proven to be excellent oleogelators due to their wide availability and low inclusion levels. However, waxes vary greatly in their compositions and contain different proportions of major components: wax esters (WE), fatty acids (FA), fatty alcohols (FaOH), and hydrocarbons (HC). In this study six waxes (bees (BW)-, sunflower (SFW)-, ricebran(RBW), carnauba (CRW)-, candelilla (CLW)-, and sugarcane wax(SCW)) are selected to develop a pairwise assessment regarding the major components. Commercial canola oil, rich in minor and polar components, and medium-chain triglycerides (MCT), as a "clean" saturated solvent, are used to elucidate the effect of solvent type on the gel forming behavior of 10% w/w oleogels. The gels are analyzed rheologically, penetronomically, microscopycally, and by calorimetry. It can be shown that the solubility and presence of polar minor components are crucial factors in oleogelation. Practical applications: Useful areas of application can be found in products with high proportions of saturated and trans fatty acids, a high potential of substitution, and can for instance include bakery-, meat-, culinary-and confectionary products.
The functionalities of wax-based oleogels in sponge cakes, a product with a high potential of substitution (fat-rich product) was investigated.
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