Phase behavior, structure and rheology of candelilla wax/fully hydrogenated soybean oil mixtures with and without vegetable oil.

Vegetable oil organogelation is one of the most promising strategies to eliminate trans fatty acids in plastic fats. Organogels prepared with edible wax are stable at refrigerator and room temperature. Some functional properties (i.e., texture) of wax organogels can be improved by adding saturated triacylglycerols. Mixtures of fully hydrogenated soybean oil (FH) and candelilla wax (CW) were studied with and without the addition of high oleic safflower oil (HOSFO). Crystallization and melting behavior, X-ray diffraction, and crystalline microstructure of the mixtures were analyzed. The elastic modulus (G'), and the structural recovery after shear of the organogels were also assessed. Mixtures without HOSFO formed solid dispersions of CW and FH crystals, where up to ~10% CW crystals were incorporated into the FH crystal lattice. The vegetable oil solutions of FH/CW mixtures crystallized from the melt, developed mixed crystal networks composed of FH crystals in the ß polymorph and CW in an orthorhombic subcell packing. As the systems crystallized in the most stable polymorph, only minor microstructural changes were shown along 28days of storage at 25°C. CW and FH crystals showed a synergistic effect on the elasticity of organogels. This was attributed to the large number FH crystals nucleated on the surface of CW crystals. The structural recovery after shear was superior for mixed organogels composed of CW platelets and grainy FH crystals compared to that of CW organogels. A recovery of up to 65.7% the G' of gels formed under static conditions was observed upon shearing.

Comparing the crystallization and rheological behavior of organogels developed by pure and commercial monoglycerides in vegetable oil.

We investigated the crystallization and rheological behavior of organogels developed with commercial (MSGC) and pure (MSGP) monoglycerides in safflower oil solutions (0.5% to 8% wt/wt). The MSGC was composed of 1-mono-stearoyl-glycerol (1-MSG, 37.7%) and 1-mono-palmitoyl-glycerol (1-MPG, 54.0%), and the MSGP essentially by 1-MSG (93.51%). The elastic (G') and loss (G″) moduli of the MSGC and MSGP-oil solutions were measured from 80°C until achieving 5°C, and then during isothermal conditions. The d(G')/d(time) rheograms, where d(G')/d(time) is the difference in G' between subsequent time-temperature conditions during cooling, followed closely the phase transition observed by the monoglycerides (MG). The d(G')/d(time) profile showed that the formation of the inverse lamellar α mesophase provided a limited structure to the vegetable oil. In contrast, the crystallization of the sub-α phase in the MSGC-oil system, and of the sub-α1 and sub-α2 phases in the MSGP-oil system structured the vegetable oil through the uptake and retention of oil within their microstructure. Additionally, smaller crystals formed the three-dimensional crystal structure in the MSGC organogels. This is in comparison with the larger crystal size observed in MSGP organogels. Nevertheless, for a similar MG concentration the MSGC organogels showed higher G' and solid fat content (SFC) than the MSGP organogels, and the differences were greater as the MG concentration increased. We consider that the mixed sub-α structure developed by 1-MSG and 1-MPG in the MSGC-oil systems favored the incorporation and retention of higher amounts of oil, in comparison with the sub-α1 and sub-α2 structures developed just by 1-MSG in the MSGP-oil systems.