The influence of incubation temperature and starter culture type on physical properties of ayran

Abstract

In this study, the effects of the incubation temperature and type of starter culture on the physical properties, including graininess and visual roughness, of ayran were determined. Ayran samples were produced from milk inoculated with two different starter cultures (Yo-Mix 410, Yo-Mix 883) and incubated at temperatures of 37 or 45°C, and then stored at 4°C for 15 days. As incubation temperature decreased the number and perimeter of grains and syneresis decreased and the amount of exopolysaccharide (EPS) increased in ayran samples. The high amount of EPS resulted in low syneresis value, the number and perimeter of grains and visual roughness in ayran samples. The apparent viscosity and consistency coefficient values of ayran samples produced from milk incubated at 37°C were higher than those from milk incubated at 45°C. The Power law model was found more satisfactory to describe flow behaviour of all ayran samples. The rheological properties of ayran samples changed with measurement temperature. As the measurement temperature increased from 5°C to 15°C, the apparent viscosity and consistency coefficient values of ayran samples were significantly decreased. The activation energy values for apparent viscosity of ayran samples varied depending on the incubation temperature, type of starter culture and storage period.