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

Karaman S., YILMAZ M. T. , Kayacier A.

FOOD HYDROCOLLOIDS, vol.31, no.2, pp.277-288, 2013 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 31 Issue: 2
  • Publication Date: 2013
  • Doi Number: 10.1016/j.foodhyd.2012.10.002
  • Title of Journal : FOOD HYDROCOLLOIDS
  • Page Numbers: pp.277-288


A 2-factor-5-level central composite rotatable design (CCRD) of response surface methodology (RSM) was used to model linear, interaction and quadratic effects of some processing variables (salep and each starch type, the composition variables) on the response variables; physicochemical characteristics (pH, brix and turbidity) and steady shear rheological properties (apparent viscosity η, consistency coefficient K, shear stress σ and flow-behavior index n) of salep–starch mixtures (SSM); namely, salep–corn starch mixture (SCSM), salep–wheat starch mixture (SWSM) and salep–potato starch mixture (SPSM). The linear, interaction and quadratic effects of the processing variables were also modeled to develop predictive models for the tested properties to optimize the effect of these variables (salep and each starch type) using ridge analysis involved with RSM. It was concluded that salep and all starch types increased the apparent viscosity (η), shear stress (σ) and consistency coefficient (K) values; decreased the flow-behavior index (n) values of SSM samples. Salep was observed to vastly increase the viscosity of mixture samples when mixed with corn, wheat or potato starches. However, potato starch exhibited very different performance as compared to the other starches in terms of the physicochemical and steady shear rheological properties. The ridge analysis used to optimize these effects revealed that maximum η (0.84, 0.46 and 1.38 Pa s), and K (16.64, 6.48 and 28.86 Pa sn) values for the SCSM, SWSM and SPSM samples, respectively would occur at salep = 0.54% and starch = 2.83% w/w.


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 delta) values of only SCSM; however, all starch types increased the storage (G'), loss (G ''), complex (G*) modulus, complex viscosity (eta*) values and decreased tan d 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 eta* 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 '', eta* 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%. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.