The influence of storage time on rheological properties and texture of yoghurts with the addition of oat-maltodextrin as the fat substitute

Yoghurts from cow's milk containing 2 kg milk fat/100 kg or 2 kg of an oat-maltodextrin/100 kg (maltodextrin included 5 kg beta-glucan/100 kg), were weighed on a laboratory scale and stored in refrigerator conditions for 21 days. Non-fat yoghurt without the addition of maltodextrin was used as a control product. The yoghurts were analysed after 1, 7, 14, and 21 days of storage. Sensory evaluation, instrumental texture profile analysis, and rheological investigations were carried out. They included the determination of the flow curves and the description by Ostwald de Waele and Casson models as well as an account of the apparent viscosity. Differences in the sensory quality of yoghurts containing milk fat or maltodextrin were not found, whereas these yoghurts were characterized by better sensory quality than the control product. The storage time had a significant influence on the sensory evaluation and the texture parameters. During the storage time, the apparent viscosity of yoghurts decreased. A decrease in consistency index value, in deviation from Newtonian flow, and yield stress was noticed, whereas in Casson's viscosity of the yoghurts, an increase was found.