Rheological characterization of triglyceride shortenings

Abstract

The rheological properties of shortenings with similar physicochemical characteristics but diverse functionality were investigated under small and large oscillatory shear. Particular attention was drawn to the mechanical behavior of roll-in shortenings, characterized for resisting work softening and forming continuous fat thin films during dough lamination and sheeting. All shortenings displayed low-frequency dependence, reminiscent of viscoelastic solids where the storage modulus is higher than the loss modulus, and displayed a comparable linear envelope, encompassing relatively small shear strains, such as those encountered in other fat systems. Linear elastic moduli and yield stress, previously used to designate roll-in functionality, remained unremarkable. In contrast, nonlinear viscoelastic behavior of roll-in shortenings differed considerably from all-purpose commercial shortenings. Lissajous–Bowditch curves suggested less local intracycle strain stiffening and less average intercycle strain softening for roll-in shortenings than other shortenings. Likewise, their Fourier spectra indicated a gradual evolution of the third harmonic into the nonlinear regime characterized by higher slopes. The third and fifth harmonics grew monotonically, and the third overtone leveled off and showed no stress decays unlike other samples, suggesting a marked ability of roll-in shortenings to withstand deformation at high stresses. Conversely, the dissipative energy scaled in a similar fashion for all shortenings. Moreover, roll-in shortenings displayed enhanced thixotropic behavior supported by lower power law indexes and prompt structural rebuilding after steady shear cessation. Overall, these rheological signatures facilitated the differentiation among the utilization of shortenings and correlated well with the functionality of roll-in shortenings.