Rapeseed Oil in New Application: Assessment of Structure of Oleogels Based on their Physicochemical Properties and Microscopic Observations

Abstract

The aim of the study was to analyze the effect of the type of gelling substance on the selected physicochemical properties of oleogels. Rapeseed oil (RO) and 5% w/w of one of the following structuring compounds (SC) were used for their production waxes: sunflower (SUN), candelilla (CAN), bees white (BW), bees yellow (BY), or monoacylglycerols (MAG). The ability of SC to form a network in RO was assessed on the basis of an analysis of the texture of oleogels (hardness and spreadability test, stability determined by the centrifugal method). Oxidative stability was determined using the Rancimat test. In addition, the microstructure of an oleogel samples was observed at a magnification of 600 times in polarized light and in a bright field. Differences in the brightness and color of the samples were also assessed using the CIELab reflection method. The highest hardness (5.52 N) and physical stability (99.67%) were found in oleogel with candelilla wax. A higher value of the force causing deformation of the sample indicates a denser network of oil gel, which was confirmed by the microscopic images analyzed in the work. The organogel with CAN had the shortest (on average 8.49 nm) and the most regularly distributed crystals compared to other samples. The lowest values of organogel strength and spreadability test parameters (e.g., firmness, work of shear, stickness, work of adhesion), which were respectively 0.73 N, 4.39 N, and 9.74 N mm, while −4.87 N and −2.68 N mm were obtained with the variant, which was yellow beeswax. Considering the texture results obtained and the centrifugal stability, it was found that organogels with yellow beeswax were characterized by the worst structuring of rapeseed oil. Sunflower wax was considered the best among the analyzed gelling agents (under the conditions of the experiment). The organogel with its 5% w/w share was distinguished by the closest to the white color and texture most reminiscent of cream. In addition, it had the highest work of shear value and the longest induction time (6.8 h) in the Rancimat test.

Influence of oil combinations on the structural properties of oleogels

“…The oil binding capacity of oleogels was determined by centrifugation as described in [5], using a CM-50 centrifuge SIA "ELMI" (Latvia). In a centrifuge tube, previously weighed, were placed approximately 1 g of oleogel and weighed again.…”

Application of Analytical Methods for the Comprehensive Analysis of Oleogels—A Review

“…For instance, rice bran wax in rice bran oil crystallizes as large dendritic crystals and the resulting network is loose and incapable of retaining the liquid oil inside it, but it also forms a fibrous morphology in other oils [42], while beeswax presented the same crystal arrangement and morphology when dispersed into medium chain triglycerides and long chain triglycerides [36]. In the study of rape seed oil oleogels, it was concluded that the more esters there are in the composition of a wax, the more needle-like a form (Figure 3) will result in the networks of structured oils; on the other hand, fat clusters irregularly distributed were observed for rape seed oil oleogel based on monoacylglycerols [66].…”

“…The microstructure of oleogels at 600× magnification, obtained by polarization (images at the top-1) and bright field (images at the bottom-2) for rapeseed oil oleogel structured with 5% sunflower wax (SUN), candelilla wax (CAN), bees wax white (BW), bees wax yellow (BY), or monoacylglycerols (MAG). Taken from Kupiec et al [66]. Copyright 2020 Creative Common Attribution License.…”

“…Rancimat tests are also performed in order to determine the oxidative state of oleogels by determining the longest induction time, which is the time from the beginning of the experiment to the starting point for oxidation [66].…”

Preparation of Protein Oleogels: Effect on Structure and Functionality

“…LMWOGs are often amphiphilic and self-assemble into supramolecular structures, building space-spanning networks [9]. Examples of LMWOGs that have been shown to form oleogels are monoglycerides [10][11][12][13][14][15][16][17][18], natural waxes [17,[19][20][21][22][23], enzymatically synthesized wax esters [24], ceramides [25], hydroxylated fatty acids [26,27], lecithin [28,29], and oligopeptides [30]. Additionally, combinations of LMWOGs have been studied, such as fatty acids and fatty alcohols [31,32], oleic acid and sodium oleate [33], sorbitan tri-stearate, tocopherol, phytosterol, β-citosterol or ceramide in combination with lecithin [34][35][36][37][38], γ-oryzanol and β-sitosterol [39][40][41][42][43], monoglycerides and phytosterols [44], beeswax and β-carotene [45], wax and monoglycerides [46], and combinations of fully hydrogenated oil, candedilla wax and monoglycerides [47].…”