Large amplitude oscillatory shear (LAOS) rheology of candelilla wax/canola oil oleogels

Candelilla wax (CW) was added in 5, 6 and 7% w/w to canola oil (CO), heating the mixtures to 90 oC, and cooling down to room temperature, to obtain CW/CO oleogels. The nonlinear viscoelastic properties of the oleogels were addressed using large amplitude oscillatory shear (LAOS) methods. To this end, Fourier analysis of the stress-time response was carried out to extract information on high-harmonic oscillatory moduli. The results showed that nonlinearities were expressed for moderate strain deformations, of the order of 1-15%. In particular, nonlinearities quantified in terms of the harmonic contributions were stronger for the elastic response (about 85-125%) than for the viscous response (less than 40%). In contrast, the mechanical response was essentially harmonic for small amplitude values, indicating the absence of nonlinearities and hence the dominance of linear viscoelastic response. Interestingly, the viscoelastic response was also linear for large strain deformation (>100%). The results reported in the present study demonstrated the viability of LAOS method for obtaining invaluable insights regarding the nonlinear mechanical response of edible oleogels made with natural waxes.

Keywords: Candelilla wax; Oleogels; nonlinear viscoelasticity; LAOS; Fourier analysis; High harmonics.