JOURNAL OF FOOD MICROBIOLOGY
Year:2019 | Volume:5 | Issue:4 |Papers Count:8

In this study the effects of nisin (a biotic preservative) (0, 0. 2 and 0. 4%) on the microbiological quality of farmed great sturgeon (H. huso) slices inoculated by Staphylococcus aureus and Escherichia coli (8 log cfu/ml) during storage (4 and-18 ° C) for 10 days was determined. The counts of S. aureus did not change significantly after ten days of storage (P> 0. 05) and in other words, it was not affected from different concentrations of nisin and storage temperatures. Frozen samples treated by nisin showed lower counts of E. coli. Nisin at both concentrations had the same effects on reducing the counts of both bacteria. The positive effects of such a low-risk biological preservative in studied food product appearing to reduce the microbial load, therefor its usage in preservation of food is industrially preferable rather than other chemical preservatives.

The aims of the present work were to evaluate the contamination rate, quantity and diversity of aerobic spore-forming bacteria in spices and herbs marketed in Tabriz. To this end, randomly 5 specimens from 25 different spices and aromatic herbs (totally 125 samples) were obtained from the groceries and shopping centers in different parts of Tabriz. The samples were analyzed using standard plate count and conventional biochemical assays. Results showed that the highest levels of mesophilic spore-forming bacteria were observed in Turmeric spice with an average of 7. 02 ± 0. 60 log cfu/g and the lowest amount of these bacteria in Coriander spice with average of 4. 15 ± 0. 56 log cfu/g was observed. From studied spices, sure with average of 4. 73 ± 0. 86 log cfu/g and the black pepper with average of 7. 20 ± 0. 81 log cfu/g had lowest and highest thermophilic spore-forming bacteria, respectively. The highest frequency of mesophilic bacteria was related to Bacillus coagulans. The most thermophilic Bacillus species in studied spices were B. macerans (16. 99 %), pantotenticus (15. 53%) and cereus (14. 7 percent). Bacillus species diversity in studied spices showed that marjoram spice had the greatest number of mesophilic Bacillus species (11 species) and Sumac spice had the highest species of thermophilic Bacillus (10 species) had the. Generally, results showed that most of the spices in Tabriz region had a high microbial load of aerobic spore-forming bacteria; and can be a source of contamination and spoilage in foods that used in their combination.

Exopolysaccharides produced by lactic acid bacteria play an important role in the improvement of sensory and textural properties of fermented dairy products. The aim of this study was to isolate and molecular identify of exopolysaccharide-producing bacteria from traditional dairy products in Kerman province. The traditional dairy product samples were collected aseptically and then cultured directly in MRS agar media. After purification, examining microscopic and macroscopic properties and performing biochemical tests, 20 strains were selected and production of EPS was measured with phenol/sulfuric acid method. The results were compared with the glucose standard curve and the amounts of production were determined. The EPS production pattern were compared with the growth pattern of the bacteria and the effects of the temperature and pH on the production of EPS were investigated. Finally, M-2 and M-26 were chosen as the top strains and identified by molecular method. Then the produced EPS was extracted and antimicrobial activity was investigated with Agar diffusion method. the results showed that the 20 isolates produced two kinds of EPS. Two isolates including M-2 and M-26 had the maximum amount of production belonged to Leuconostoc mesenteroides and Enterococcus faecium respectively. The production of the EPS in the PH 6. 5-8 under the temperature 25-42˚ C were investigated and the results showed that the maximum amount of production was at the 37˚ C and pH=7. 5 in the end of logarithmic growth. The results of this study indicate EPS production is possible by traditional dairy products of Kerman province.

Since most probiotic foods are dairy products and with regard to changing the taste of people, dairy product manufacturers are trying to develop new products, which have high nutritional value, in addition, provide variety for consumer ‘ s satisfaction. Nowadays, flavored yogurt has a wide adoption among consumers. The flavoring of yogurt is made by adding natural ingredients such as a variety of fresh or dried fruits and vegetables such as mint, pennyroyal, basil and shallot. In this study, the effects of adding Iranian shallot at 0/2, 0/3 and 0/4% on the viability of probiotic bacteria (Lactobacillus acidophilus and Bifidobacterium lactis) and some physicochemical (pH, titratable acidity, syneresis and viscosity) and overall acceptability of lowfat stirred probiotic yogurt containing 0/08 percent beta-glucan was investigated. The results showed that the addition of shallot affected significantly titratable acidity and pH of yogurt samples (p<0. 05). With increasing the percentage of shallot, the viscosity and the viability of probiotic bacteria of stirred yogurt samples were decreased and syneresis and overall acceptability were increased (p<0. 05).

Food is a vital substance which is important for human life. Although this vital matter could be a vehicle for transferring the microorganisms to human and Shigella is an important microorganism which could be cause of dysentery to human, the present study tried to isolate and characterized isolated Shigella from food. In this study 100 food samples including: 40 types of vegetables, 30 chicken, 20 minced meats and 10 fish have been collected. The samples were inoculated to gram negative broth and transferred to differential media such as MacConkey and Salmonella Shigella agar. Then the suspected colonies were identified using biochemical tests. Afterward, the isolates were characterized using ipaH gene by PCR technique. Furthermore, they were analyzed using serotyping techniques and the antibiotic susceptibility pattern were checked. Out of 100 foodstuffs the bacteria were detected only from vegetables. The isolates (n= 6) were confirmed by molecular techniques and all of them belong to the genus of Shigella. In addition, the slide agglutination test showed that the isolates were belong to sh. dysentriae (n=1), Sh. sonnei (n=2), Sh. flexneri (n=2), and one non detectable. Furthermore, they showed different antibiotic pattern, as the isolate No. 1 showed 100% sensitivity to the tetracycline and were resistant to the others. Although foodstuffs are so important in transferring the microorganism, the monitoring of foods in market and greengrocery is necessary.

In this study, optimum conditions for extraction of the alcoholic extract of Vaccinium macrocarpon by soaking method and its antibacterial effects were determined by Response Surface Method. Extraction was carried out at a temperature of 5 to 60° C, 2 to 10 hours, and the sample to solvent ratio of 4 to 20%, and an ethanol / methanol solvent ratio of 0 to 100%. The antimicrobial effects of the extracts were evaluated by detection of MIC and MBC against Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus and Escherichia coli bacteria. The optimum operating conditions to obtain the maximum amount of Cranberry extract were at 60° C, 10 hours, and the sample to solvent ratio 11. 43% and the ethanol to methanol ratio 88. 88%. In these conditions, the extraction yield was 4. 88%. Extraction yield of cranberry extract was predicted based on the mathematical model was 5. 17%. This value is close to the value predicted by the model indicates a relatively good performance model. Alcoholic extract of Vaccinium macrocarpon resulting antibacterial activity and influence on the growth of all bacteria was tested. Gram-positive bacteria were more sensitive than gram-negative bacteria. Bacillus cereus and E. coli, had the most and the least sensitivity to the alcoholic extract of Vaccinium macrocarpon. So that they had the lowest and the highest values of MIC and MBC among bacteria respectively.

Helicobacter pylori can cause gastrointestinal diseases such as gastritis, stomach ulcer and gastric cancer. The main treatment for this disease is antibiotic therapy, but due to the length of treatment and the damage caused by the use of antibiotics, alternative treatments are needed. It seems that the use of herbs is the best alternative for treatment of the disease. The purpose of this study was to investigate the effect of eggplant yogurt enriched with alcoholic licorice extract on Helicobacter pylori inhibition. Extract of licorice was added to eggplant yogurt samples at concentrations of 0. 1, 0. 2, 0. 3, 0. 4 and 0. 5%. Control sample (extract free) was prepared. The samples were kept at 4 ° C for three weeks. Microbial, physicochemical and sensory properties of the samples were investigated. The minimum inhibitory concentration (MIC) of alcoholic licorice extract by micro dilution method against Helicobacter pylori was 7000 ppm and the minimum bactericidal concentration (MBC) was 10000 ppm. The highest diameter of inhibition zone was related to the eggplant yogurt sample containing 0. 5% licorice extract and the lowest was belonged to control sample (eggplant yogurt without licorice extract). Adding the licorice extract to the eggplant yogurt samples decreased significantly acidity and syneresis (p<0. 05). The addition of licorice extract improved overall acceptance of eggplant yogurt. Among the samples, the sample containing 0. 5% licorice extract was selected as the best treatment. Therefore, eggplant yogurt containing licorice extract has suitable sensory quality and can be affected the inhibition of Helicobacter pylori.

The use of nitrite as preservative and color stabilizer in meat products like hams is common. Due to its carcinogenic effects, it has negative track record among consumers. On the other hand, low concentrations increase the risk of Clostridium botolinum growth during storage and the production of toxin of botulism. By replacing this preservative with warm and natural pear wood smoke, in suggested situations, a safe product without having carcinogenic affects can be produced. Therefore, the general objective of this study was to investigate the effect of hot and natural wood smoke on the quality of chicken ham without nitrite at 15, 30, 45 and 60 minutes. In this study, treatments were smoked by warm and natural pear wood for 15, 30, 45 and 60 minutes after production, vacuumed and kept for 50 days under refrigerate condition (1-4 ° C) and were examined physicochemical, microbial and the amount of compounds Benzo-a-Pyrene in 10, 20, 30, 45, 50 days. The results showed that there was a significant difference between moisture content, protein, ash and control in other treatments (P≤ 0. 05). There was a significant difference between the control and other treatments for microbial characteristics (Clostridium perfringens) (P≤ 0. 05). And the residual amount of Benzo-a-Pyrene was evaluated in fumigated treatments within the standard range(P<0. 5μ g/Kg). Relying on chemical and microbial results, treatments without nitrite and smoked for 45 and 60 minutes, were the best among other treatments in comparison with the control treatment.