Rheological properties of set yogurt during gelation process: II. Impact of incubation temperature

The effect of incubation temperature on the rheological properties of set yogurt during the gelation process using a cylindrical rotational viscometer was carried out in this study. Fresh raw milk was standardized (3% fat), heated at 90°C for 3 min using a plate heat exchanger and homogenized at 13.79 Mpa. The homogenized milk was divided into 3 parts (450 ml each), inoculated with 3% yogurt starter culture (Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus) and incubated at 40, 45, and 48°C. The optimum incubation temperature for acid development was observed at 45°C. The minimum viscosity was at 40°C, the maximum viscosity at 48°C. These results indicated that incubation temperature affected yogurt viscosity during the gelation process. Increasing the incubation temperature decreased the flow behaviour index and increased the consistency coefficient.