RHEOLOGICAL STUDY OF INTEGRAL YOGURTS AT DIFFERENT TEMPERATURES

Yogurts are one of the most consumed foods in the whole world, making them successful for every age. Produced from a mix of milk and specific dairy ferments has high nutritive properties, assisting and bringing health benefits. In order to improve the development of these products and reduce losses in the industry, it is important to carry out technological studies with an emphasis on rheological properties in order to design pipework and equipment for quality control in the industry. This study has as its objective to study rheological varieties of commercial integral yogurts. The study compared the influence of temperatures, using 6, 36 and 45°C because of the temperatures of the storage, the mouth, and the process, respectively. The commercial yogurts analyzed had pH, acidity, ash, moisture, protein, and total fat results within the limits imposed by the legislation. The fluid's behavior in relation to viscosity is influenced by time, so the phenomenon of thixotropy occurs and it is necessary to break it after 40 min so that it is possible to see the fluid's viscosity behavior in relation to the influence of temperature. The rheological characteristics of the yogurt can be affected by adding fat and protein, and can show viscosity changes, analyzing two different brands of integral yogurt confirmed that the concentration has a significant impact on the necessary shear stress for the yogurt to flow and observed that in high temperatures the initial tension was lower. So according to the experiments, the average initial tension in 6, 36 and 45°C was 91,16 Dinas/cm², 27,20 Dinas/cm² and 3,81 Dinas/cm², respectively. Therefore, when the temperatures get higher the shear stress get lower, as expected because, the yogurt has pseudoplastic behavior in different temperatures and the mathematical model that better fixed was Herschel-Bulkley.