Influence of exopolysaccharide producing starter cultures and incubation temperatures on the physical and rheological properties of low fat set type yogurt
Special Symposium - Innovations in Food Technology (LMC Congress)
White BioTech & Related Processes (Food-2b)
Keywords: Low fat, set yogurt, Rheology, Synersis, Incubation temperature, Exopolysaccharide
Different strains of yogurt starter cultures and different incubation temperatures were investigated in the production of low fat set yogurt. Milk samples were incubated with 2% X-11 (exopolysaccharide (EPS) producing) and CH-1 (non-EPS producing), and then incubated at 37, 42 and 45Ċ until the pH reached 4.7. Whey separation, water holding capacity (WHC), firmness, storage modulus (G’) and loss modulus (G”) were measured as quality criteria on the yogurt samples. Firmness of samples was measured using Universal Testing Machine. The constant crosshead velocity of 0.5 mms-1, to a sample depth of 35 mm and maximum force (N) to penetrate the probe in 35mm depth was recorded. Rheological properties were determined using a UDS-200 rheometer by means of frequency sweep with the measurement of storage modulus (G’) and loss modulus (G”). Test conditions were frequency 0.1 to 50 Hz. and maximum strain was < 0.05, to maintain in linear viscoelastic region.
Results showed that all determined parameters was influenced by starter culture type (except firmness) and incubation temperature, (p<0.05). Interaction effect only on firmness was significant. Maximum values of firmness, G’ and G” in samples of both starter cultures was found in 42Ċ. Increase in incubation temperature and using EPS producing culture resulted in higher WHC and lower synersis, storage and loss modulus values. Synersis was decrease more with EPS producing culture produced at 37Ċ than with yogurts made with non-EPS producing culture at higher incubation temperature.
