Mathematical approach for two component modeling of salep–starch mixtures using central composite rotatable design: Part II. Dynamic oscillatory shear properties and applicability of Cox–Merz rule

Dynamic shear rheological properties of salep–corn starch mixture (SCSM), salep–wheat starch mixture (SWSM) and salep–potato starch mixture (SPSM) samples were determined using a 2-factor-5-level Central Composite Rotatable Design (CCRD). Salep increased loss modulus (G″) values, and decreased loss tangent (tan δ) values of only SCSM; however, all starch types increased the storage (G′), loss (G″), complex (G∗) modulus, complex viscosity (η*) values and decreased tan δ values. At various salep and starch combination levels, a remarkable synergistic effect was observed in the dynamic shear properties. Potato starch exhibited completely different rheological performance in terms of G′, G″ and η∗ values. Salep did not obey the Cox–Merz rule; however, a modified Cox–Merz rule was applicable for SCSM and SPSM samples. The ridge analysis revealed that maximum G′, G″, η* and G∗ values for the SCSM, SWSM and SPSM samples would occur at salep = 0.54% and 0.26%, respectively, and each starch type = 2.83%.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Dynamic shear rheological properties of salep–starch mixture were investigated. ► Central Composite Rotatable Design was used for the modeling of the parameters. ► All starch types increased the storage, loss, complex modulus and complex viscosity. ► A remarkable synergistic effect was observed in the dynamic shear properties. ► Salep did not obey Cox–Merz rule; however, a modified Cox–Merz rule could be applied.