فهرست مطالب a. ahmadi-dastgerdi

Pet birds have close contact to human and resistant bacteria can transfer from birds to intestinal flora of human.

This study was carried out to determine the tetracycline resistance genes in Escherichia coli strains associated with enteric problem in pet birds.

Totally, 295 cloacal swabs were collected from 195 healthy and 100 diarrheic pet birds in Isfahan province, Iran. The presence of E. coli was identified by conventional bacteriological, biochemical, and molecular examinations. The presence of tetracycline resistance genes (tetA, tetB, tetC, tetD, tetE, tetG, tetK, tetL, tetM, tetO, and tetS genes) were examined using three multiplex PCR.

The results showed that 18.9% and 43% of cloacal samples of healthy and diarrheic pet birds contained E. coli, respectively. The mean percentage of E. coli isolated from cloacal samples of diarrheic birds was significantly higher than the healthy birds (46.6 vs 23.1%). In healthy birds, out of 37 E. coli isolates, 10 isolates were resistant to tetracycline, harboring tetA and tetB genes (3 tetA vs 7 tetB), but in the diarrheic birds, of 26 resistance E. coli, 11, 12, and 3 strains contained tetA (42.3%), tetB (46.15), and tetA+tetB (11.53%) genes. The percentage of tet genes were significantly higher in diarrheic birds than healthy birds (58.9 vs 24.0%).

Both resistant genes of tetA and tetB were detected in E. coli isolates that are related with efflux pump activity. These genes can be transferred between Gram-negative bacteria and they have the potential ability to be transferred to the environment and human flora.

Nowadays essential oils are considered as substitutes for synthetic additives in food products. Since the lipid oxidation is the main chemical process affecting mayonnaise deterioration, in this research, the antioxidant activity of essential oil ofthyme(Zataria multiflora boiss)was determined for oxidative stability of treated mayonnaise (homogenized) during 6 months of storage.
The antioxidant activities of the essential oil of thyme(0-150 µg/g) were investigated by DPPH method. The efficiency of this essential oil (144.4 µg/g) as a natural antioxidant in mayonnaise was studied by peroxide, anisidine, totox and thiobarbituric acid values.
GC analysis of the essential oil resulted in the identification of forty compounds. The essential oil characterized by a high number of monoterpenes such as thymol and carvacrol. Regarding anti-oxidation, the investigated essential oil strongly reduced the DPPH radical (IC50=144.4 g/ml). This study confirms that the essential oil of thymepossessed antioxidant properties in vitro. The results showed that the treatments containing essential oil and TBHQ significantly reduced the oxidation (p<0.05), while the control sample was oxidized faster. The essential oil had a significant effect on taste, odor and overall acceptance, but no significant difference was observed in color and texture.
The results of the present experiments suggest that essential oil of thyme(Zataria multiflora boiss)can be used as a source of natural antioxidant for the application in food industries to prevent lipid oxidation particularly lipid-containing foods such as mayonnaise. Therefore, it can use as a natural antioxidant and flavoring compound in foods such as mayonnaise.

Achillea millefolium is one of the oldest known medicinal plants, due to the presence of certain chemical compounds are used traditional and modern medicine. One of the most important medicinal properties of Yarrow, its antimicrobial effects on a wide range of pathogens in humans and animals. The in vitro antimicrobial and antioxidant activities of the essential oil from leaves of Achillea millefolium subsp. millefolium were examined. GC-MS analysis of the essential oil resulted in the identification of fifty-eight compounds constituting 98.71% of the total essential oil of leave. The essential oil of leaves were characterized by a high number of monoterpenes borneol (12.32%), 1, 8-cineole (10.51%), β -pinene (9.33%) and α -pinene (8.82%). Regarding anti-oxidation, the investigated essential oil from leaves strongly reduced the diphenylpicrylhydrazyl radical (IC50=0.94 mg/ml). This essential oil showed antimicrobial activity as well against Staphylococcus aureus, Salmonella enteritidise, Escherichia coli, Penicillium glaucum and Saccharomyces cervesiae (MIC values 0.45-7.20 mg/ml). This study confirms that the essential oil from leaves of Achillea millefolium possessed antioxidant and antimicrobial properties in vitro.

Oil in water emulsions have attracted considerable attention in food industry due to their large applications. In this study, the effect of thermal treatment on oil in water emulsions (o/w) containing 40% oil was studied. The emulsions were prepared using xanthan gum, guar gum and carboxymethyl cellulose as stabilizer and polyoxyethylen sorbitan monooleat as emulsifier. A mixture design was used to define the percentage of each stabilizer to simulate wide range of emulsions. The emulsions were pasteurized at 87 ºC for 15 minutes. Thermal treatment had a considerable influence on rheological properties of the emulsions. Viscosity of all emulsions decreased after thermal treatment and stabilizers had increasing effect on this response. All emulsionsexhibited non Newtonianpseudo plastic flow behaviorthat often referred to as shear thinning (n<1). A non linear relation between shear rate and shear stress was observed. Shear stress versus shear rate data was successfully fitted to the Power-law model. Consistency coefficient (K) decreased and flow behavior index (n) increased after thermal processing. Thermal treatment caused an increase in particle size of emulsions because of coalescence. Some of emulsions had heterogeneous coalescence (bimodal) and some of them had homogenous coalescence (mono modal). All emulsions were stable to centrifugation and did not breakdown. It was found that surface tension was affected more by temperature than by stabilizer content. Surface tension decreased by thermal processing. Viscosity of all the samples was reduced during storage. The results showed that developed emulsions are thermally under pasteurization temperatures.