Determination of effect of homogenization and heat treatment applications on physicochemical and sensorial properties of ayran produced from milk with different fat content

In this research, during storage period, the effects of different homogenization and heat treatment applications on physicochemical and sensorial properties of ayran produced from milk with different fat content were determined. Milk with different fat contents (0.1, 1.0 and 2.0%) standardized to 8% total solids was used in the ayran production. The milk was homogenized at different pressure (single stage homogenization; 150 and 300 bar, two stage homogenization; 150/50 and 300/50 bar). Ayran produced from unhomogenized milk was the control group of the study. The homogenized and unhomogenized milks were heated at 95°C for 256 s and at 95°C for 80 s. After heating, the milks were cooled to 42°C, inoculated 2% ayran stater culture and incubated at 42°C until pH reached to 4.6. After incubation, the samples were cooled to 20°C, and 0.5% salt was added to samples. The ayran samples were stored at 4°C for 30 days, and physicochemical and sensorial properties of the ayrans were determined on day 1, 15 and 30 of the storage. The effects of heat treatment, homogenization, fat rate and storage period on the titratable acidity, pH, syneresis and apparent viscosity values of the ayran samples were found be statistically significant (P<0.001). Based on the results of rheological analysis, the power law model was more accurate for ayran samples. The flow behaviour index and thixotropy values of ayran samples increased as the severity of heat treatment and homogenization presure increased. The flow behaviour index and thixotropy values of ayran samples decreased as fat rate and storage period increased. Acording to results of sensorial analyses, the effects of heat treatment, homogenization, fat rate and storage period on the structure scores of the samples were found to be insignificant (P>0.05). The effects of heat treatment and storage period on the taste scores of the ayran samples were found statistically significant (P<0.001), while the effects of homogenization and fat rate on the taste scores of the samples were found statistically insignificant (P>0.05). The effect of fat rate and storage period on the appearance scores of the ayran samples were found statistically significant (P<0.001), while the effects of heat treatment and homogenization on the appearance scores of ayran samples were found statistically insignificant (P>0.05).