نشریه بهداشت مواد غذایی
پیاپی 2 (تابستان 1390)

Consumer's interest over natural preservatives and their application as food ingredients is growing, which encourage complementary researches on various natural antimicrobials such as plant essential oils. Sumac (Rhus coriaria L.), is a plant that is used as a flavouring agent in Iranian traditional foods. Therefore, in this study Sumac essential oil composition and antimicrobial activity was evaluated. Sumac ssential oil was extracted with distillation and analyzed by gas chromatography method. Antimicrobial effect of Sumac essential oil against Salmonella typhimurium, that is considers as one ofimportant pathogen in food, was evaluated. Antimicrobial effect of essential oil was evaluated by measuring turbidity as a result of bacterial growth at a broth media by Bioscreen C instrument at 35°C. Result showed that the most important fraction of essential oil that may have antimicrobial effect is Caryophyllen. Although Sumac essential oil had bacteriostatic effect at low concentration of 30 ppm, it showed bactericidal activity at high concentration of 1000 ppm. It could be concluded that, Sumac essential oil by its antimicrobial fractions can be used to control the growth of Salmonella typhimurium in food stuff.

Yersinia enterocolitica is a pathogenic organism that has recently emerged world-wide and its incidence is increasing. Human infection with Y.enterocolitica could cause diarrhea, abdominal pains, appendicitis like syndrome, vomiting, fever and septicemia. The main sources of human illness include pork, beef, milk vegetables, water and wild and domestic animals. This study was carried out on 300 meat samples including 100 beef, 100 lamb and 100 poultry samples at retail of Shahre-kord. The samples were transferred to PBS containing sorbitol. After 21 days of incubation at 40C, samples were cultured on CIN agar supplemented with CIN antibiotics. Putative colonies were confirmed by biochemical tests. Results showed that, 42 (14%) of samples including 4(4%) beef, 4(4%) lamb and 34(34%) poultry samples were contaminated with Y.enterocolitica. According to results of this study, intensive hygienic measures should be considered during slaughtering, storage and distribution of different kinds of meat.

Zoonotic bacterial diseases are considered as the most important human infectious diseases. In this category, a disease that transfer and infect human through food has an special role. Among foods with animal origin, eggs due to their application as food ingredient in food products, like sauces, spices, ice creams and other food products that may use in half cooked or crude forms, always has the potential to transfer microbial pathogens to human. This study is about to prove that presence of remainder feces on eggshells leads the penetration of bacterial agents into egg yolk. A total of 120 daily egg samples (with and without fecal contamination) were collected from henneries around Tabriz and transferred immediately to microbiology laboratory. After performing microbial examinations (using BHI Broth, BHI Agar, Blood Agar, Selenite F, Tetrationate, XLD,SS Agar),Gram Staining, Oxidase and Catalase tests, bacteria of eggshells and egg yolks has been identified. Out of 120 eggs, 15.83% bacterial contaminants were found in egg yolks samples. Among them, 73.68% were gram negative and 26.31% were gram positive. Among gram negatives, Pseudomonas with occurrence of 8.3% and in gram positives group, Bacillus with abundance of 4.16% were the most frequent bacterias. Also in samples collected from eggshells, 99.16% of the eggs demonstrated bacterial contamination which 23.55% of positive samples were among gram negative group and 76.44% were gram positive. The most contribution of eggshell gram negative bacterias were relevant to Pseudomonas, E.coli, Proteus and Citrobacter with respectively 18.33%,10.83%,5.83% and 4.16% rations. Among gram positive bacteria that isolates form eggshell samples for the most frequent bacterias, were Bacillus, Staphylococccus, Streptococcus, Rhodococcus and Micrococcus with respectively 80.00, 34.16%, 15%, 9.16% and 7.5% rations. Use and consumption of eggs with shells contaminated with faces in food products is a serious risk factor for human health and can lead to zoonotic bacterial diseases by transferring bacterial pathogens.

Antibiotic residues in food stuff and their transmission to the consumers have some consequences such as bacterial resistance, allergic reactions, intoxication, carcinogenic effects and disturbing of intestine natural flora of. Four-plate test is among microbiologic methods for detecting antibiotic residues in food stuff, which performs in four culture media with different pH values and test bacteria. In this study, 30 samples including gluteal muscle, diaphragm muscle, liver and kidney tissues obtained randomly from beef carcasses slaughtered in Tabriz abattoir were assayed. From total 30 kidney samples, every 30(100%) cases; among 30 liver samples, 28(93.33%); from 30 diaphragm samples, 22(73.33%) and from 30 gluteal muscle samples, 22(73.33%) cases were diagnosed as positive for antibiotic residues. Results revealed that, the most antibiotic residues belonged to Penicilin and Macrolides groups (P<0.05). In addition, kidneys was diagnosed as the most contaminated tissue for antibiotic residues (P<0.05).

Histidine is one of non-protein nitrogen extractives which found in fish such as Salmonidae family (trout is belonged this family).Members of this family has high amounts of Histidine compared to other foods. Some Salmon microbial flora can decarboxylated Histidine to Histamine and this metabolite is a hazard component for human. Evaluation of Histamine levels in Salmon via a fast and accurate method can be useful for decreasing the intensity of these hazards. In this study evaluated psychrophilic and mesophilic aerobic bacteria and also histamine level in purchased salmon samples from fish markets in Tehran by ELISA method (Rida Screen Histamine Kits). A total of 60 samples of Rainbow trout (Oncorhynchus mykiss) purchased from fish markets and assayed for Histamine by using Rida Screen Histamine ELISA Kits. Bacterial enumeration was performed on 10-fold diluted samples at 25°C and 35°C for mesophilic and psychrophilic bacteria, respectively. The range of Histamine content was 4 to 28mg/100g (14.18mg/100g). 12.50 percent of samples had Histamine content above the international standard level (20mg/100g). Data achieved by bacterial enumeration and ELISA test were analyzed by Pearson correlation test indicated that direct relationship between histamine and the number of bacteria in fish samples is established (p<0.01). Variations in amounts of bacterial decarboxylase enzyme in all kind of fish depends on with time – temperature storage, fish species variation and kind of seafood. Therefore, application of good health care during the various stages of breeding, fishing, transportation and storage in inhibition of bacterial growth and subsequent production of histamine is effective and the risks of histamine poisoning can be minimized thereby.

Osmotic dehydration is a process of partial removing of water from food by immersion of the product in a hypertonic aqueous solution. This study aimed to investigate the effect of osmotic dehydration on quality of hot- air- dried onion. Azarshahr red onion variety was used for the experiments. In order to define an optimum condition for osmo-drying process, some parameters including temperature, time and concentration of dehydration solution was evaluated. Based on water loss(WL) and solid gained (SG), the best treatment of temperature, time and concentration of dehydration solution were determined as 40°C, 1 h and %5 respectively. One series of samples were prepared and dried in oven at 65°C for 12 h. These samples were packed in two different ways including aluminium foil under the pressure of inert gas and in polyethylene packs. The samples were kept in ambient temperature. Every 2 months during storage period, parameters such as rehydration and organoleptic properties were performed on the samples.The results organoleptic test revealed that, the quality of samples decreases after 4 months of storage.Moreover, the samples that were packed by polyethylene showed the most desirable properties. Among osmoticsamples, the degree of rehydration of the sample prepared with concentration of % 5 in 40°C in 1 hour and packed in foil under inert gas, was greater than the other osmotic samples. Rehydration parameters had direct relation with temperature and the time of rehydration. Therefore, the amount of rehydration improves with increasing time and temperature.

Listeria spp. Has been isolated from poultry, red meat products and fish in many countries around the world. Listeria monocytogenes has been isolated from water and ice used for relating freshness of food. Chiller water could possibly increase the microbial contamination of poultry carcasses in slaughter-house. Therefore, the aim of this study was to investigate the effects of water chiller on Listeria monocytogenes contamination of poultry carcasses before and after chilling process in four industrial slaughter house of western Azarbaijan province was investigated. 180 poultry carcasses from 4 industerial slaughter house in western azarbaijan was investigated for Listeria monocytogenes befor and after chilling process using the modified Canadian version. All of the isolated belongs to the serogroup 1 and 4. Paired – samples T test indicated significant difference (P<0.05) between the contamination levels before and after chilling process.

Thyme (Zataria multiflora Boiss) cultivated in Iran is extensively used as flavoring agent in dairy products. Also it has antimicrobial effects on the pathogenic bacteria which cause some food borne diseases. The aim of this study was to evaluate the antimicrobial effect of this plant’s essential oil on Escherichia coli O157:H7 in white brined cheese, considering the organoleptic properties of cheese. The essential oil of Z. multiflora Boiss. was obtained by hydrodistillation and analyzed by GC/MS. Preliminary sensory tests were carried out to establish the upper level of the essential oil incorporation. At the end of storage time, evaluation of the sensory characteristics of the supplemented cheeses suggested that, Z. multiflora Boiss. essential oil’s concentrations more than 200 ppm in cheese milk had adverse effects on the taste and odor of cheeses. Therefore, further examinations were carried out with 0, 100, 150 and 200 ppm concentrations. The inhibitory effects of different concentrations of the Z. multiflora Boiss. essential oil on E. coli O157:H7 were determined by enumeration of the microorganism on selective media and comparing the bacterial counts in different groups. The inhibitory effect of Z. multiflora Boiss. essential oil at concentration of 200 ppm was higher compared to its lower concentrations and also compared to the control groups. No significant difference (P > 0.05) was observed between the pH values of control groups and treated samples. Incorporation of Z. multiflora Boiss. essential oil at concentration of 200 ppm into cheese milk had significant antibacterial activity (P<0.05). However, when these kinds of essential oil has to be recommended for cheese safety, issue of strong taste and smell should be addressed.