Abstract

Recently, probiotics and their extracted bacteriocin are used in food preservation especially in fermented foods as drinking yoghurt. Lactobacillus gasseri (Lb. gasseri) is widely recognized as one of the important porbiotics and has potential healthy role in suppressing the growth of some spoilage and pathogenic bacteria by its bactriocin. Bacteriocin of Lb. gasseri was extracted and its antibacterial activity was detected against (Bacillus subtiles, Staph. aureus and E.coli) by agar diffusion assay. Lb. gasseri and its extracted bacteriocin were inoculated separately in the examined drinking yoghurt samples. All groups were examined for T.A%, microbiological examination and sensory evaluation at time of production and weekly till signs of spoilage were detected. Obtained results revealed that the drinking yoghurt group samples which contain Lb. gassri bacteriocin showed the lowest T.A% and highly significant inhibitory effect on the examined pathogenic and spoilage microorganisms with improved sensory evaluation, as well as it could extend their shelf life up to 42 days during refrigerated storage. On conclusion, Lb. gasseri and its extracted bacteriocin showed strong antibacterial activity against the examined pathogenic bacteria and can be applied for safe food preservation with prolonged shelf life.

Key words: Probiotics; lactobacillus gasseri; bacteriocin; drinking yoghurt; antibacterial activity; fermented milk.