An Attempt to Relate Oleogel Properties to Wax Ester Chemical Structures

Abstract

Wax esters are considered to have a dominant contribution in the gelling properties of wax-based oleogels. To understand their gelling behavior, oleogels of seven different wax esters (total carbon number from 30 to 46; c = 10% [m/m]) in medium-chain triglycerides oil were characterized. Scanning electron microscopy revealed that wax esters crystallize in rhombic platelets with a thickness of 80 to 115 monomolecular layers. Bright field microscopy showed that the regularity and face length of the crystals increased with the total carbon number and molecular symmetry of the respective wax ester. Oscillatory rheology was used to characterize the gel rigidity (Gmax*). Here, wax ester oleogels with smaller total carbon numbers yielded higher Gmax* values than those of wax esters with higher total carbon numbers. The gel rigidity (Gmax*) inversely correlated with the crystal face length. Smaller and optically less well-defined platelets promoted higher gel rigidities. In the case of the microstructure of a specific oleogel composition being manipulated by a variation in the cooling rates (0.8; 5; 10 K/min), this relationship persisted. The information compiled in this manuscript further elucidates the crystallization behavior of wax esters in oleogels. This contributes to the understanding of the composition–structure–functionality relationship of wax-based oleogels supporting future food applications.

Food-Grade Oleogels: Trends in Analysis, Characterization, and Applicability

“…The advantages of monoglycerides as oleogelators are that they can crystallize and form strong networks even at low concentrations (3%) [1]. As shown in numerous studies, the crystallization mechanism of monoacylglycerols consists of the formation and growth of a laminar crystal network, and some of the oleogel properties (thermal stability, mechanical properties) can be controlled by the chain length, molecular weight, and concentration of monoacylglycerols [2][3][4][5][6].…”

“…Recently, research in the field of oleogels has focused on investigating new molecules or combinations of molecules that can act as structuring agents, as well as developing new methods for gelation. This includes exploring different types of structuring agents, such as waxes [3][4][5][6][7][8][9][10] and polymers [11,12], and investigating their properties and interactions with liquid oils to create stable and functional oleogels [13,14]. Scientists are also investigating the use of new techniques, such as micro-and nano-structuring [15][16][17][18][19][20][21][22][23][24], to modulate oleogel properties and create novel structures with specific functionality [17,[25][26][27][28].…”