Effect of hydrogel/oleogel ratio, speed and time of mixing, on the mechanical properties of bigel materials and the application of Cox-Merz rule

Bigels, are materials that combine hydrogels and oleogels. However, a major problem with them is the characterization of a single material compound by two materials that have different physical characteristics. The objective of this research was to evaluate the effect of the mixing time, the interaction of ratio hydrogel/oleogel, mixing rate and the applicability of Cox-Merz rule in bigels. Bigels were obtained blending monoglycerides, canola oil for oleogel phas, esters of polyglycerol with linearly esterified polyricinoleic acid, Polyoxyethylene sorbitan monostearate (Tween 60), guar gum and water. The bigels were prepared by incorporating the oleogel into the hydrogel and mixed at different ratios (67:33, 83:17; 85:15), followed by stirring at two different rate (600 and 800 rpm) for 20 min. Firmness was evaluated for all experimental samples. Thermal scanning was done by DSC. Steady Shear and Oscillatory test were carried out on the samples. Creep- Compliance test, and Cox-Merz rule were used for data analysis. Texture analysis indicated that a higher level of oleogel in the bigel, diminished firmness, however, major differences were observed between samples at low rate of agitation and high time of mixing. The creep test was modeled by Burgers model with good fit (R2 > 0.9). High recovery (66–67%) was observed at lower presence of oleogels and high mixing rate. Data of steady shear and oscillatory shear were adjusted to empirical Cox-Merz rule with good fit at low shear rate (> 10 s−1).