Effects of cysteine and different incubation temperatures on the microflora, chemical composition and sensory characteristics of bio-yogurt made from goat’s milk

Yogurt and bio-yogurts were made from goat’s milk using a starter culture and probiotic culture, with or without cysteine addition (0.5%). Incubation was carried out at 37 and 42 °C until pH 4.6 was reached and yogurts were stored 4 ± 1 °C for 14 days. Yogurts were analysed 1, 7 and 14 days after production. The addition of cysteine, incubation temperature and storage time significantly influenced overall properties of the samples. During storage, whey separation, pH and acetaldehyde decreased, while lactic acid increased. Viable bacterial counts in all bio-yogurts were above 107 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 and supplemented with cysteine, in comparison to other samples. This indicates that lower temperature incubation and addition of cysteine can be used satisfactorily for the manufacture of bio-yogurt.