DETERMINATION OF FLOW AND VISCOELASTIC PROPERTIES OF THE KYRGYZ ETHNIC FOOD “SÜZMÖ” DEPENDING ON TEMPERATURE AND MOISTURE CONTENT

Abstract

Consumer interest in concentrated protein-rich food is growing. Kyrgyz traditional food Süzmö, which is a highly viscous dairy product that is produced from fermented milk Ayran, needs to be introduced into the dairy industry. In this study, the rheological parameters of this indigenous food product were investigated in steady and dynamic rheological experiments. The flow behaviours of Süzmö were evaluated at six temperatures (20, 30, 40, 50, 60, and 70°C) and suitable rheological models were found. The flow curves of Süzmö at investigated temperatures have the yield stress (τ0) values between 32.64 Pa and 285.87 Pa. The flow properties of Süzmö samples at 20 and 30°C correspond to the Bingham model. The Casson model was suitable for describing flow curves at 40, 50, 60, and 70°C with correlation coefficients R=0.9506 ‒ 0.9973. The effective viscosity (ƞeff) of Süzmö decreased from 15.88 to 0.26 Pa·s with increasing temperature from 20 and 70°C. The effect of temperature on the viscosity corresponds to the Arrhenius relationship. The calculated activation energy was 61.66 kJ/(mol). A linear model was defined taking into account the influence of moisture content (p>0.05) on effective viscosity (ƞeff) and yield stress (τ0). A temperature-sweep was performed at 20 to 80°C to determine the thermal denaturation of the fermented milk samples. The measured parameters are essential for the industrial production of Süzmö and other concentrated fermented milk products.