Effects of water and salt level on rheological properties of ayran, a Turkish yoghurt drink

Ayran is a yoghurt drink traditionally manufactured by mixing yoghurt with water and salt. The effects of different levels of water and salt on the rheological properties and serum separation during storage of traditionally manufactured ayran were investigated. Ayran samples were prepared by the addition of water at levels of 30 or 50 g 100^-1 and salt at levels of 0, 0.5 or 1 g 100 g^-1 and stored at 4°C. All samples exhibited non-Newtonian behaviour with shear-thinning and slight thixotropy was observed in some of the 30 g 100 g^-1 water-containing samples. The rheological properties of ayran samples were determined by using the power law model. The consistency coefficient decreased and the flow behaviour index increased dramatically with increasing levels of water and salt. Increasing the levels of added water and salt resulted in more serum separation. Proper adjustment of the amount of water and salt during the manufacture of ayran was necessary to obtain optimum consistency and to prevent serum separation during storage.