مجله میکروب شناسی مواد غذایی
سال یکم شماره 1 (تابستان 1393)

Biogenic amines are small organic molecules formed by decarboxylase enzymes caused by bacteria in foodstuff. This study investigated the concentration of biogenic amines of putrescine and histamine in the fish stored in ice for an eighteen-day period in three day intervals using chromatography (days of 3، 6، 9، 15 and 18). In this study، the amine of histamine was not detected in the first and third day of storage; but putrescine was about 1. 30±0. 03 micrograms in the third day. The first day of detection of the both biogenic amines was the sixth day of storage. The primary concentration of histamine and putrescine was 1. 51 and 1. 30 micrograms per gram respectively، and was reach to 14. 5 and 19 micrograms per gram respectively at the end of the period. Analysis of the results by ANOVA test indicated that there was a significant difference (P<0. 05) in the concentrations of these amines between the first day (0) and the last day of storage. In addition، there was a significant relationship among the mesophilic bacterial load، increase of histamine، the psychrophilic bacterial load and the biogenic amine of putrescine (P<0. 05).

In this study، the total phenols and antioxidant activities of Apium petroselinum essential oil (APEO) were determined and it''s antibacterial effects on seven food spoilage and pathogenic bacteria was in vitro studied. Having extracted the essential oil، the total phenols were determined colorimetrically and the antioxidant activities evaluated by bleaching of β-Carotene. Its antibacterial effects in the form of the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were determined by Micro Dilution method against Alcaligenes faecalis، Providensia rettgeri، Serratia marcesens، Klebsiella oxitoka، Staphylococcus aureus، Shigella dysenteriae and Listeria monocytogenes. The results revealed that the amount of total phenols was 8. 18±0. 45 mg/g equivalent with Gallic acid and the antioxidant activities were 45±1. 52 %. In addition، the APEO had antimicrobial effects on the above bacteria. The minimum inhibitory concentration (MIC) was between 1. 562 and 12. 5 and the minimum bactericidal concentration (MBC) was between 3. 125 and 25 mg/ml. Therefore، APEO، because of having phenolic contents، enjoys antioxidant activities and antibacterial effects recommending as a suitable preservative in food industries.

Salmonellosis، caused by bacteria from the genus Salmonella، is one of the most common foodborne illnesses and is manifested by diarrhea، mild fever، nausea، abdominal pains and even death. Its traditional diagnosis is based on culture، biochemical and serological techniques and for more accurate diagnosis several molecular methods have been developed. The epidemiology and prevalence of these bacteria in chicken meat samples is essentially unknown in Iran. in this study in order to isolation and characterization of Salmonella spp. 620 chicken meat samples were collected from supermarkets in Chaharmahal Va Bakhtiary Province، Iran. Genomic DNA was extracted from each sample and multiplex PCR method was developed. Results showed that 28 out of 620 samples (4. 51%) were positive for Salmonella spp. and from these isolates 12 samples were S. typhimurium (1. 93%)، 10 samples were S. enteritidis (1. 61%) and 6 samples were other species of Salmonella (0. 96%). Results revealed that all of S. typhimurium and S. enteritidis isolates have virulence factors. Our results indicated that Salmonella spp. can contaminated chicken meat samples and it is essential to control the hygienic quality of chicken meat samples especially in slaughterhouse.

The aim of this study was to evaluate antimicrobial effect of Butylated Hydroxy Anisole alone and in combination with EDTA against S. typhimurium and L. monocytogenes in culture media and Iranian White Cheese. At the first phase، Minimum Inhibitory Concentrations (MIC) of Butylated Hydroxy Anisole and EDTA against bacteria were measured. The samples of cheese made from pasteurized milk where infected experimentally with S. typhimurium and L. monocytogenes. They were divided as a control and other samples that have values of 2500، 5000 and 10000 μg/ml of BHA، and combination of 2500، 5000 and 10000 μg/ml of BHA and EDTA. In the next phase of study، bacteria were counted at different days. The results obtained from this study showed that using combination of BHA and EDTA can properly reduce number of S. typhimurium and L. monocytogenes in culture media and Iranian white cheese. This study demonstrated that BHA can be used for increase shelf life of Iranian white cheese

Helichrysum arenarium L. is a perennial herbaceous plant that belongs to asteraceae family and traditionally used to treat various diseases in many countries. In this study، the essential oil from the aerial parts of the H. arenarium L. was extracted with hydro-distillation using a clevenger approach and then its antimicrobial effects was studied on the growth of two yeasts species، Candida albicans and Saccharomyces cereviciae، using micro-dilution method at ten different concentrations. The results of this study indicated that the essential oil of H. arenarium had significant effects on reducing and eliminating tested yeasts (P< 0. 05) but C. albicans with MIC=195. 31 and MFC=3125 μg/ml indicated more resistant than S. cereviciae so that growth of S. cereviciae in all concentrations was lower than that of the C. albicans. The results revealed that the essential oil of H. arenarium had a significant anti yeast activity (P<0. 05); therefore، it can be used as an antifungal agent in the food and pharmaceutical industries.

Presence of the Fruit juice spoilage bacteria، including Bacillus spp.، can be problematic in fruit juice industry. The aim of this study was to isolate and identify the bacteria being able to tolerate orange juice pasteurization conditions. In this study، 16 samples of orange juice were prepared and investigated in sterile conditions. 0. 5 ml of each sample was inoculated in orange serum agar medium and incubated at 43 °C. The isolates were identified using biochemical and antibiogram tests. As a result، From 16 prepared samples، 2 samples were contaminated with bacteria. The bacterium isolated from these samples was able to grow at up to 50 °C on Orange Serum agar. This isolate was then identified as Bacillus licheniformis using the classification system of Linnaeus. Despite of having no pathogenic nature and producing the spores resistant to temperature and acid، Bacillus licheniformis is of great importance according to the viewpoint that it can be mistaken in primary detection by Bacillus of fruit juice which are the spoilage agents and differentiated tests should be done to separate them from Alicyclobacillus spp. for preventing from presenting wrong report. Furthermore، the isolation of these bacteria indicates the inappropriateness of processing conditions to eliminate bacteria from fruit juice that may provide possibilities for growth of fruit juice spoilage bacteria.

The fungi producing mycotoxins reduce production of agricultural crops and cause irreparable loses to public health. Aspergillus is one of the most important fungi in the environment being capable to grow in nearly all compounds and organic materials and their conidia are substantially scattered in the water، soil and air. Cuminum ciminum and Satureja hortensis are Iranian herbal medicines having many therapeutic effects. The aim of this study was to evaluate the inhibitory effect of Cuminum and Satureja nano essences on Aspergillus species isolated from fish meal produced by factories in Mazandaran Province. Twelve Aspergillus species isolated from 89 fish meal samples and inhibitory effect of Cuminum and Satureja nano essences were evaluated by micro dilution. The highest and least numbers were related to Aspergillus fumigatus and Aspergillus nidulance، respectively. The MIC and MFC foe different species was in the range of 1. 56-6. 25 and 3. 12-25 μg ml-1. The results revealed the high effectiveness of the nano essence on Aspergillus species.

Smoked Doogh and Doogh flavored with Pistacia atlantica Subsp. Kurdica essential oil (mastic resin) are popular products in Kurdistan region. Anti-pathogenic effects of these essential oils have been shown in many studies. However، their effects on lactic acid bacteria in dairy products have never been investigated. Therefore، the aim of this study was to evaluate the effect of these essential oils on Lactobacillus bulgaricus. After isolation and purification of L. bulgaricus from Doogh، Mueller Hinton Agar was used for Disk Diffusion method to assess the susceptibility of the bacteria in different concentrations of the essential oils (0. 1، 0. 2، 0. 3، 0. 4، 0. 5، 0. 6، 0. 7، 0. 8، 0. 9، 1، 2، 3، 4، 5 and 100%). The minimum inhibitory concentration for mastic resin and liquid smoke were 0. 1% and 0. 9 %، and the zone of inhibition was 11 and 6. 5 mm، respectively. Furthermore، the inhibition zone diameters increased with the increasing in essential oil’s concentrations. According to the result of this study، L. bulgaricus is susceptible to mastic resin essential oil. Therefore، it will be recommended that using this essential oil should be restricted in dairy products. Furthermore، there is no problem in using it in fermented products containing L. bulgaricus in less than 0. 9% concentrations of liquid smoke. At whole، the effect of essential oils on lactic acid bacteria should be investigated، before using them in dairy products.