Optimization of viscoelastic properties of low-fat stirred yogurt using mixture-process variable experiments

In this study, the effect of different amounts of konjac gum (KG) (0 to 0.2%) and sage seed gum (SSG) (0 to 0.2%) as experimental variables of the mixture design and fat content (0 to 3%) and homogenization rate (0 to 24000 rpm) as experimental variables of the process design on the viscoelastic characteristics of low-fat stirred yogurt were investigated. Based on the results of stress sweep test for different samples, the storage modulus (G') had a value more than the loss modulus (G''), explaining a solid-like behavior of the samples. Also, according to the stress sweep test, G' LVE (G' at linear viscoelastic region), G'' LVE (G'' at linear viscoelastic region), γc (critical strain), τy (yield stress), τf (yield stress at flowing point), and Gf (elastic modulus at flowing point) of the samples were significantly increased, especially for samples containing higher sage seed gum, with increasing fat content and homogenization rate. To optimize the properties in this study, G" LVE were considered to be minimum and G' LVE, γc, τy and τf were considered to be maximum. According to the mentioned properties, the optimized amount of KG was 0.19%, the amount of SSG was 0.01%, the fat content was 0.59% and the homogenization rate was 12075 rpm.