The Effects of Fat and Non Fat Dry Matter Concentration and Storage Time on the Physical Properties and Acidity of Yoghurts Made with Probiotic Cultures
The effects of fat and non fat dry matter (NFDM) concentration and storage time on the physical properties and acidity of yoghurts made using commercial probiotic cultures (ABY and ABT-1) were investigated by using response surface methodology. All yoghurts made with ABY and ABT-1 cultures exhibited shear thinning behaviour. The power low model was used to describe the shear thinning behaviour of yoghurt samples. The flow behaviour index ( n) and the consistency coefficient ( m) were determined. NFDM levels in milk strongly affected syneresis, apparent viscosity at a constant speed of 100rpm, flow behaviour index and the consistency coefficient. Titratable acidity and pH were mainly affected by the storage time. Under all conditions examined, yoghurt made with ABT-1 culture had higher apparent viscosity, consistency coefficient and pH value than those of the yoghurt made using ABY culture.