Viability of Lactobacillus acidophilus (L. acidophilus) and Bifidobacterium bifidum (B. bifidum)
incorporated with yoghurt culture in three combinations of starter cultures; Treatment 1 (yoghurt culture + L.
acidophilus), T2 (yoghurt culture + B. bifidum) and T3 (yoghurt culture + L. acidophilus + B. bifidum) were studied.
Analyses of pH, titratable acidity (TA), syneresis, acetaldehyde content and sensory evaluation after 1, 3, 7, 14 and 21
days of cold storage of yoghurt were under taken. Counts of L. acidophilus was recorded 5.85 log10 cfu g-1 in T1 which
were higher than counts in T3 (5.79 log10 cfu g-1) at the end of storage period. On the other hand, the viability of L.
acidophilus and B. bifidum was stable until 14 days of storage period. The results showed that the addition of B. bifidum
to yoghurt culture (T2) increased TA of bio-yoghurt comparing with addition of L. acidophilus (T1). Syneresis in all
treatments was in the range of 20 to 33% and it was found higher in T3 than control. The highest sensory values were in
control, T1 and T2 until the end of 14 days of storage period.