Mechanical properties of wax-oleogels: Assessing their potential to mimic commercial margarine functionality under small and large deformations.

Utilizing waxes to gel oils presents a viable approach for diminishing trans and saturated fat levels in commercial fats such as margarines. This technique ensures that oleogels mimic traditional fats in terms of rheological properties, oil-binding capacity, and overall structure. Our study employed cooling-shear rates to finely adjust physical characteristics, evaluating rheology via SAOS-LAOS, oil retention, and crystal structure of wax oleogels, compared against commercial margarines as benchmarks. Findings indicate that wax oleogels, under specific cooling/shear conditions, exhibit softer yet more ductile-like behavior, akin to margarine, while retaining oil effectively. This similarity is evidenced through Lissajous curves and plastic dissipation ratio during yielding, reflecting a ductile yielding response characterized by square-like Lissajous curves and a plastic dissipation ratio index approximating one. Although these crystallization conditions influence the mechanical properties of wax oleogels, they do not alter oil losses or wax characteristics.

Thermoresponsive oil-continuous gels based on double-interpenetrating colloidal-particle networks.

Gels composed of multicomponent building blocks offer promising opportunities for the development of novel soft materials with unique and useful structures. While interpenetrating polymer networks have been extensively studied and applied in the creation of these gels, equivalent strategies utilizing colloidal particles have received limited scientific and technological attention. This study presents a novel class of thermo-responsive apolar double gels from interpenetrating networks of attractive colloidal silica and lipid particles. These double gels are easily assembled and suitable for the fabrication of 3D-printed edible soft constructs. Emphasis is focused on the rheological properties and structure emerging on the dilute regime (ϕ ≲ 0.1). Rheological investigations demonstrate that double gels exhibit greater stiffness and resilience to yielding compared to their single lipid gel counterparts. The scaling behavior of the oscillatory linear shear moduli and the critical strain for yielding with volume fraction remain comparable between single and double gels. Creep yielding in double gels exhibits two exponential decay regimes, suggesting the presence of thicker gel strands undergoing flow. Visualization and quantification of the quiescent microstructure confirms the existence of such denser aggregates devoid of larger clusters due to steric hindrance of interpenetrating networks in double gels. This is in stark contrast to lipid single gels where aggregates grow unrestrictedly into larger clusters. Our study constitutes the first demonstration on the assembly of apolar double gel networks as a promising avenue for the design of novel soft materials and foods with tailored structure and mechanics.

Linear and nonlinear rheological behavior of fat crystal networks.

Fats are ubiquitous in biological membranes, foods, and many other commercial products. In these, they play essential roles in biological, nutritional, and physical functions. In this review, we focus on physical mechanical functions. The rheology of fats arises from the crystal network, which displays hierarchical structural levels from the molecular to the mesoscopic. Under linear deformations, the crystal network behaves as a viscoelastic solid with elasticity dictated by particle concentration and microstructural features as represented in fractal rheo-mechanical models. Under nonlinear deformations, the crystal network yields, showing a variety of nonlinear phenomena, i.e., softening, stiffening, thixotropy. These features largely contribute to functionality or performance as essentially all processing and end-uses of fatty materials involve large nonlinear deformations. Early work on rheology of fats gave hints of their nonlinear mechanical behavior, although in many cases the measured properties were empirical. In contrast, recent efforts from our group measured fundamental rheological functions using large amplitude oscillatory shear rheology. We demonstrate the ability of this technique to discern among the bulk functionality of bakery fats (all-purpose and lamination shortenings) based on well-defined rheological signatures that also relate to the fat structure. This technique has the potential to provide similar insights on other fatty systems and novel ideas for reformulation and design of alternative lipid-structuring materials.