RESUMEN

The food industry confronts an enormous challenge to develop stable margarine-type water-in-vegetable oil (W/O) emulsion-based table spreads with reduced concentration of saturated fat and without trans fats. In the present work, we developed a gelled W/O emulsion (Gelled-W/O-E) containing 20% of water using a mixture of a conventional W/O emulsion (W/O-E) stabilized with glycerol monostearate (GMS), and an ethyl cellulose (EC) oleogel. The mechanical, microstructure and stability of the resulting gelled emulsion (Gelled-W/O-E) was compared with control systems consisting of conventional W/O emulsions (W/O-E) and EC-GMS oleogels (EC-GMS-O; no water added) formulated using the same GMS (0.5% and 1.0%) and EC (7%) concentration as in the Gelled-W/O-E. The Gelled-W/O-E showed higher elasticity and emulsion stability in comparison with the control systems. This in spite the EC and GMS concentrations used were below the minimal concentration required to develop a gel, and the tentatively lower solid content in the Gelled-W/O-E than in the EC-GMS-O because the presence of water. We observed that by increasing the GMS concentration in the Gelled-W/O-E, the water droplet size decreased as gel elasticity and W/O emulsion stability significantly increased. We associated this behavior to a synergistic GMS-EC interaction that kept the GMS at the water-oil droplet interface. These results showed the role of water droplets as active fillers in determining the rheological properties of the Gelled-W/O-E, and that the GMS efficiency as emulsifier increased in the presence of EC in the oil phase. After comparing the microstructural properties of commercial margarine spreads with those of the Gelled-W/O-E, we concluded that the structured W/O emulsion is a novel way to achieve similar functionality to margarine spreads, without the use of saturated and trans-fats.

Asunto(s)

Agua , Celulosa/análogos & derivados , Emulsiones , Compuestos Orgánicos , Reología

RESUMEN

The gelation process, elasticity, and mechanical recovery after shear were studied in mixed oleogels of ethylcellulose (EC), monoglycerides (MG), and candelilla wax (CW). EC oleogels produced without MG showed grainy texture due to incomplete dissolution of crystalline fractions of raw EC in the vegetable oil (150 °C). These fractions were eliminated by dissolving the raw EC/MG mixture in ethanol, evaporating the solvent, dispersing, and dissolving the solid residue in the vegetable oil (150 °C) prior gelation. The EC polymeric network, and MG, and CW crystals had a positive interaction on the elasticity of mixed oleogels. Mixed oleogels produced under static conditions showed a 100 % of elasticity recovery after shearing, a phenomenon associated with an EC interchain hydrogen bonding mediated by hydroxyl groups of MGs. This tentatively resulted from the formation of junction zones of the type EC-[MG]n-EC. The rheological behavior of these olegels was remarkably close to that of commercial shortenings.

RESUMEN

In this study we investigated the combined effect of shearing and cooling rate in the rheology of organogels developed in high oleic safflower oil by (R)-12-hydroxystearic acid (HSA), its primary amide derivative [(R)-12-hydroxyoctadecanamide, HOA], and the N-octadecyl derivative of HOA [(R)-N-octadecyl-12-hydroxyoctadecanamide, OHOA]. The experimental set up to develop the organogels involved: 1). The use of quiescent (0s-1) or shearing (300, 600, and 1200s-1) conditions during cooling the gelator solutions (2%) just until achieving the gelator's melting temperature (TM) in the vegetable oil, to then continuing the cooling under static conditions until achieving 15°C) The use of cooling rate protocols involving a constant cooling rate of 1°C/min (CR1) or 10°C/min (CR10) in the shearing and static stages, or variable cooling rates in each stage (i.e., VR1-10 or VR10-1). The elasticity of the organogels (G') was measured while cooling under static conditions, once the systems achieved 15°C, and after 60min at this temperature. The rheological results obtained at 15°C showed a cooling rate and molecular weight-dependent effect of shearing on G'. We propose that the molecular relaxation time of gelator molecules, and its increase as molecular weight increases and as temperature decreases, plays an important role on the gelator's susceptibility to go through a shear induced crystallization process. Therefore, high molecular weight molecules like OHOA (551.97Da) would remain stretched by shearing longer times than HSA (300.49Da) and HOA (299.49Da). Thus, when shearing was applied while cooling at the higher cooling rate (i.e., CR10 and VR10-1), the stretched OHOA molecules would lead to the development of mesophase precursors that upon further cooling under quiescent conditions, crystallize developing a well-structured organogel. In contrast, stretched low molecular weight molecules (i.e., HSA and HOA) with shorter relaxation time would dissolve back to the isotropic state during cooling. Additionally, the rheological results of HSA and HOA organogels suggested that the shear induced crystallization process might be dependent on the gelator polarity also. These results show that the application of shear and the extent of its application as temperature decreases until achieving TM, have important implication on the self-assembly of gelator molecules, and therefore in the organization and rheology of the three-dimensional crystal network of the organogel.

Asunto(s)

Frío , Geles/química , Reología , Cristalización , Elasticidad , Tecnología de Alimentos , Peso Molecular , Transición de Fase , Aceite de Cártamo/química , Estearatos/química , Termodinámica

RESUMEN

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.