This research aimed to study the antibacterial activity of some natural preservative materials (rosemary, garlic, onion, black cumin, thyme, parsley, celery essential oils, Kombucha, propolis ethanolic extract 20% and propolis
water extract 20%) compared with the antibacterial activity of some chemical preservatives which may be used in dairy products and their effects on characteristics of yoghurt. The antibacterial activity of these preservative materials was studied on some spoilage and pathogenic bacteria (Bacillus
subtilis subsp spizizenii ATCC 6633, Escherichia coli ATCC 14169, Streptococcus pyogenes ATCC 21060 and Staphylococcus aureus ATCC 29737), through, the inhibition zone and the minimuminhibitory concentration
(MIC). The results indicate thatthe inhibition zone for thyme recorded the highest level ranging from 16 mm for Str. pyogenes to 24 mm for Staph. aureus followed
by celery and rosemary. While, the inhibition zone of propolis water extraction (20%) and onion essential oil recorded the lowest. The effect of using some natural preservative materials in yoghurt manufacture on the keeping quality, sensory evaluation, chemical composition, microbiological analysis and rheological properties of the obtained product was evaluated. The results cleared that the Kombucha (3 & 4%), ethanolic extraction of propolis (0.1%), black cumin essential oil (0.1%) and parsley essential oil (0.05 & 0.1%) can produce yoghurt with good organoleptic, rheological properties and prolonged shelf life for 28 days. |
