Two types of yoghurt with Rosmarinus officinalis oil was prepared and stored up to 21 days. The extract plant was added at the rate of 0.14, 0.21, 0.29, and 0.36 g/L. Yoghurt samples were analyzed for some physical, chemical, microbiological and sensory some characteristics. The total and fecal coliform count, Staphylococcus aureus count, Salmonella count, yeast and mold counts were determined in yoghurt samples at two, seven and 21 days of storage period. There were significantly differences between the control and enriched yogurts in the dry matter, lactose, ash and protein contents. No germ detected in all samples during the storage period. Sensory analysis indicated that the highest flavour, taste and texture, of the two yoghurt types added was with 0.14g/L of essential oil among the yoghurts samples.

Abstract:The in vitro antimicrobial and antioxidant activities of the exopolysaccharide (EPS) extracted from yoghurt starter were investigated. Antimicrobial activity tests were carried out using disc diffusion methods with Escherichia coli, Staphylococcus aureus and Streptococcus D, Proteus spp and the yeast of Candida albicans. The antioxidant properties were evaluated using the test of DPPH free radical trapping. The results show that the EPS has weak antimicrobial activity against the tested strains with inhibitions zones ranging from 9 to 13 mm. EPS could reduce the free radical (DPPH) to diphenylpicrylhydrazine a yellow-colored at 24.25% showing antioxidant activity less than that of ascorbic acid which was 69.79%.

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The inhibitory effects of five commercial extracts (Allium sativum, Chamaemelum nobile, Thymus vulgaris, Zingiber officinale and Ricinus communis ) against Alternaria alternata were tested three concentrations (2.5, 5, 12.5 µl/ml) in vitro. T. vulgaris and R.communis extracts both exhibited the most effective antifungal activity against A. alternate with diameter of inhibition zones of 54 mm. The C. nobile extract exhibited a lower degree of inhibition 24.5 to 45 mm at three concentrations. The antifungal indices of T. vulgaris and R.communis extracts at three concentrations against A. alternata were all 98.14%, while this of C. nobile extract was 43.52% at 12.5 µl/ml. The results show that the five commercial extracts have potential for the development of natural antifungal agents, which could be an alternative to chemicals for control of phytopathogenic fungi on fruits or vegetables.