Effect of different incubation temperatures on the microflora, chemical composition and sensory characteristics of bio-yogurt

Yogurt and bio-yogurt were made using a starter culture and a probiotic culture. Incubation was carried out at 37°C and 42°C until pH 4.6 was reached and the yogurts were stored at 4+1°C for 14 days. Yogurts were analysed 1, 7 and 14 days after production. In the samples the levels of acetaldehyde, lactic acid, titratable acidity and whey separation were determined. Viable bacterial counts and sensory assessment were also determined. The incubation temperature and storage time significantly influenced overall properties of the samples. During storage, whey separation, pH and acetaldehyde decreased, but titratable acidity and lactic acid increased. Viable bacterial counts in all bio-yogurts were above 10 7 cfu g -1 at the end of storage. Whey separation, titratable acidity and lactic acid contents were lower, while acetaldehyde and viable bacterial counts were higher in the bio-yogurts incubated at 37°C in comparison to bio-yogurt incubated at 42°C. This indicates that lower temperature incubation can be used satisfactorily for the manufacture of bio-yogurt.