مجله میکروب شناسی مواد غذایی
سال چهارم شماره 3 (پاییز 1396)

This study was aimed to investigate the antimicrobial effects of black cumin oil in sausage and evaluate the possibility of reduction of its nitrite. For this purpose, sausage samples were prepared at concentrations of 2 and 3 percent of black cumin oil containing various amounts of nitrite (including 0,30,60,90 ppm) in eight treatments and a control sample without black cumin oil and with 120 ppm nitrite and all stored for a month at 4°C. Then microbial properties of all samples such as total bacterial counts, coliforms, Salmonella, Escherichia coli, Staphylococcus aureus, Clostridium perfringens, yeasts and moulds were examined on 1, 11, 21 and 31 days of storage time and organoleptic properties were evaluated after production of samples. The results showed that treatments containing 2 and 3 percent of black cumin oil with 90 ppm and 60 ppm nitrite, mainly had total bacterial counts, coliforms counts, E.coli, S.aureus, yeasts and moulds counts similar to those had control sample during the storage. But these microbial counts showed significant increase in all the samples at the end of the storage period (P

This Study aimed to investigate the indicators spoilage chemical and shelf life of consolidated burger (silver carp- hen) during 6 months of storage at -18 ºC. For this purpose, fish and hen samples with 5 treatments: 1(75% fish숫憢 pen), 2(without fish% pen), 3(56.25% fish.75 pen), 4(18.75% fish 56.25% pen) and 5 (37.5% fish.5% pen) with 3 frequency were produced. The results showed quality deterioration indices were increased during storage. The most of PV (4.08±0.01 meq O2 kg-1), TVB-N (20.26±0.92 mg N2 100/g), TBA (3.63±0.06 mg Malonaldehyde/kg) and FFA (3.94±0.03%) were evaluated in the 1 treatment in sixth month. Comparing to the first month, the psychrophilic bacterial counts (PTC) and total viable count (TVC) values were significantly delayed in samples 4 and 5 treatments. Freezed silver carp burger stored at −18 °C retained very good quality, with respect to growth of PTC and TVC bacteria. Considering the results, the best shelf life of consolidated burger was fourth month in the 2 treatment.

The aim of this study was to evaluate the chemical composition and antimicrobial activity of essential oil of Turnip (Brassica rapa) root in Fars-Iran. The essential oil was obtained by hydro-distillation and analyzed by gas chromatography-mass spectrometry (GC-MS) which revealed 16 compounds in which Methyl chavicol (32.31 %), Trans anethole (19.58 %), Linalool (15.46 %), α-Pinene (9.28 %), α- Thujone (6.59 %) and β- Pinene (3.34 %) were the main components. The antimicrobial activity was measured by disk-diffusion and micro-dilution method for determination of MIC and MBC. The results showed that the essential oil of turnip has a significant effect in reducing the growth of bacteria have been tested. However the essential oil had the lowest MIC on (MIC=2.5 mg/ml) E. coli but the results showed the highest effects against (MIC=0.625 mg/ml) S. aureus. Results presented here suggest that the essential oils of turnip possesses antibacterial properties, and is therefore a potential source of active ingredients for food industry.

So far, transmission pathways and epidemiological aspects of Helicobacter pylori are not identified well. Role of water and food materials in transmission of Helicobacter pylori to human is probable. The present study was carried out to genotyping of Helicobacter pylori strains isolated from the samples of raw milk and dairy products collected from Isfahan province. In total, 250 samples of milk and dairy products were collected and transferred to the laboratory. DNA extraction was done and detection of 16S rRNA gene of the Helicobacter pylori was performed using from the PCR test. Positive samples were analyzed for presence of various genotypes of VacA and CagA. From a total of 250 samples of milk and dairy products, 37 samples (14.8%) were infected with Helicobacter pylori. Sheep milk had the highest (25%) and traditional cheese (2%) had the lowest rate of infection. Statistically significant difference was seen between the type of sample and prevalence rate of Helicobacter pylori. VacA s1a (27.02%), VacA m1a (24.32%) and CagA (21.62%) were the most frequently detected genotypes. S1am1a (16.21%) and s1am2 (5.40%) genotypes had the highest frequency amont combined genotypes. Genotypic similarity of Helicobacter pylori strains of various samples represented their similar source of infection. Genotypic similarity pattern of our study and conducted studies on clinical samples of human represented transmission of Helicobacter pylori strains from infected staffs of milking and saling of milk and dairy products to samples.

Probiotics are defined as a live microorganism that when administrated in an adequate amount promote the health status of consumers. The most important challenge in consumption of probiotics is how to keep them alive during food processing and throw the digestion system. The aim of this study is the comparison of the effects of sub-lethal pre-culturing on the viability of Lactobacillus plantarum and Lactobacillus fermentum. in this study the effect of sub-lethal stresses such as low pH (2.5, 3.5, 4.5, 5.5, 6.5), Salt (2, 4 %), bile (0.2, 0.4, 0.8, 1 and 1. %) and Cold (4 °C) on increasing of viability of cells was investigated. The survival rate of treated and untreated cells in yogurt and digestion system using the enumeration of viable cells was also comprised. the results showed that sub-lethal pre-culturing had a significant effect on the viability of cells (P≤0.05). The viability of treated cells was increased in all stresses, moreover, the number viable cells in the stool sample of consumers showed a significant increase after one-month consumption of yogurt. the results demonstrate that sub-lethal pre-culturing was led to increasing the number of viable cells in all mentioned stresses, while the increasing rate of viability was different between two bacteria.

In recent years, Bacteriocins have been recognized as natural preservatives in food and drug industries, also, nowadays, they are used as substitutes of chemical antibiotics for treatment of infections. Bacteria in probiotic dairies recognized as “Lactic Acid Bacteria”, are significant group of bacteriocin producing bacteria. In this study 15 isolates have been isolated from native dairies of Kerman province. The Bacteriocins were purified by sulfate ammonium method. The effect of produced bacteriocins on different indicator gram negative and positive strains was investigated. The effects of trypsin, pH ranges, and heat on the produced bacteriocin were investigated too. The isolate that produced the most bacteriocin with the most antibacterial activity, identified as Enterococcus faecium Y1.The maximum antibacterial effect was observed against Listeria monocytogenes and Pseudomonas aeruginosa. The produced bacteriocin lost activity in presence of trypsin. It was resistant against pH ranges from 2 to 12 and heat ranges up to autoclave temperature. The produced bacteriocin had a wide antibacterial activity spectrum against the gram positive and negative bacteria, in particular pathogenic bacteria, also was resistant against heat and pH ranges. As a result, use of bacteriocin in food and drug industry, as animal feed, and as a substitute for chemical antibiotics is recommended.

Mastitis is inflammation which causes physical and chemical changes in milk and pathological changes in mammary gland. The aims of present study were identification of bovine mastitis causative agents in Isfahan and survey of bee Propolis and Pollen antibacterial effect on the isolated bacteria. Milk samples were aseptically obtained from 10 mastitic cattle. The isolated bacteria were detected based on macroscopic, microscopic and biochemical characteristics. Ethanol and acetone extracts were prepared from Propolis and Pollen by soaking and the antibacterial effects of them determined using well plate and microdilution methods. The isolated bacteria included Streptococcus agalactiae, Staphylococcus aureus, Corynebacterium sp., Listeria sp., Pseudomonas aeruginosa and Escherichia coli. Well plate method showed that Propolis and Polen extracts were effective on Gram-positive bacteria but had no effect on Gram-negative ones. The mean of results showed maximum effects of Pollen acetone extract on Streptococcus agalactiae (concentration of 12.5 mg/ml) and Pollen ethanol extract on Corynebacterium (concentration of 12.5 mg/ml). Acetone extract of Propolis showed maximum effect on Staphylococcus aureus (concentration of 25 mg/ml) and Listeria sp. (concentration of 12.5 mg/ml). The results were confirmed by minimum bactericidal concentration analysis. Extracts of propolis and pollen showed powerful effects on Gram-positive isolates and this effect was more detected by acetone extracts.

The residue of antibiotics and other chemical compounds in chicken meat is one of main concerns in consumers of this protein source. In this research, for study of correlation between antibiotic consumption and chicken meat contamination, in summer of 2014, 10 chicken farms in Isfahan province that reared under conventional condition and 5 chicken farms that reared broilers under without antibiotic consumption were monitored from start of growing period. At end of growing period, in slaughter stage, one piece of breast muscle and cecum content were sampled. The percentage of carcass contamination and number of Escherichia coli (E.coli) in cecal content were determined in chickens reared under conventional and without antibiotic condition. Also, the shigatoxogenic E.coli was examined by PCR.Furthermore, the carcass contamination and E.coli colony count in cecal content in chickens with or without colibacillosis background were determined. The results showed that the chicken meat contamination to E.coli and the E.coli population in cecal content in chickens reared under conventional condition were not significant different from chickens reared without antibiotic, while these indices in chickens with colibacillosis history were significant higher than chickens without colibacillosis history. In this study the shigatoxogenic E.coli was not detected. In overall, this study revealed microbial infection in chicken farms that lead to antibiotic consumption could decrease hygienic quality of chicken meat. Therefore, in addition to controlling of withdrawal time for antibiotic consumption, the withdrawal time for infections incidence must be observed for decrease the risk of transmission of pathogens along the food chain of human.