Comparative studies of Listeria monocytogenes survival in bifidus and traditional yoghurt during production and storage

Huda E. Othman; Hamdi M. Abdelsamei; Adham M. Abdou.; Ekbal M. A. Ibrahim and Azza, H. Elbaba1


Antagonistic activity of Bifidobacterium bifidum against Listeria monocytogenes during the production and storage of Traditional yoghurt (TY) (Streptococcus thermophiles+ Lactobacillus bulgaricus) and Bifidus yoghurt (BY) samples (Streptococcus thermophiles+ Lactobacillus bulgaricus+ Bifidobacterium bifidum). Traditional & Bifidus yoghurt samples were inoculated with 106 cfu/g L. monocytogenes and stored for 21 days at 4±1oC. Samples were taken at zero time (fresh samples) then after 3, 5, 7, 10, 14 and 21 days of storage for titratable acidity measurement and bacterial count of the culture starters and L. monocytogenes counts. The results revealed that the titratable acidity of TY & BY was increased during the 21 days of storage, while the population of L. monocytogenes became non-detectable level in 10th days of storage in BY and still detected in TY till the day 14th of storage and became 2.20± 0.31 log10 cfu/g. The count of all starter cultures (S. thermophiles+ Lb. bulgaricus+ B. bifidum) in both yoghurts increased during the fermentation and cold storage and remained stable with values >6 log10 cfu/g throughout the storage period at 4±1°C.

Key words

probiotics, Bifidobacteria, L. monocytogenes, yoghurt, bifidus yoghurt

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