JOURNAL OF FOOD MICROBIOLOGY
Year:2017 | Volume:4 | Issue:1|Papers Count:8

Unpasteurized as traditional ice cream production in Iran is very common due to the increasing use of herbal compounds as inhibitors of microbial growth, this study to examine the antibacterial effects of Lemon juice against Staphylococcus aureus and Escherichia coli in Ice cream prepared in the laboratory. In order to do it, ice creams containing concentrations of 1, 2, 5, and 10% lemon juice was prepared. The samples were inoculated with bacterial suspension containing 105 cfu/gr. The samples were stored in the freezer -20oC. During the time of 1, 2, 3, 7, 14 and 21 days, antibacterial effects of various concentrations of lemon juice was evaluated after culture in specific media. The results showed that in all concentrations, significant difference was observed between the number of bacteria with the control group (P<0.001) and the greatest antibacterial effect was observed at concentrations of 10% and at 7, 14 and 21 days. The average number of S. aureus in compared with the E. coli significantly was lower (P<0.001) showing more sensitivity of these bacteria. Reducing the number of bacteria increase over time and in the third week the greatest reduction in the average number of bacteria was observed. Overall, the results suggest that lemon extract has antibacterial effects against bacteria tested in traditional ice cream so, using it can be considered as a natural preservative in order to reduce poisoning.

Cream enabled the growth of most microorganisms due to the adequate moisture, pH close to neutral, and nutrient rich. The major cause of bitter flavour in cream is degradation of proteins to the hydrophobic peptides by protease enzyme derived from the thermostable bacteria resistant to the pasteurization temperature. The present study was aimed to investigate and molecular identify of bacteria spp. causing bitter flavour in pasteurized cream. The pasteurized cream samples were collected, then microbiological tests such as total count of microorganisms, psychrotrophic bacteria count, coliform bacteria count, thermostable bacteria count, sporogen bacteria count and also chemical tests such as acidity and pH measurement were carried out. The tests were fulfilled with three repetitions at 4oC and 15oC in first, third, fifth, seventh, ninth, and eleventh days after the cream production. The isolates causing bitter flavour in creams were identified by physiological, biochemical, phylogenetical, and molecular methods. The bacterial isolates were inoculated into the pasteurized creams and assayed for changing in flavour. The two species of bacteria causing bitter flavor were isolated from the pasteurized creams. The sequencing of 16S rRNA gene of isolates indicated that they were Bacillus cereus and Bacillus subtilis. The temperature of preservation is one of the most important agents of microorganisms’ activity and dairy product durability. Keeping raw milk for a long time before the pasteurization leads to increasing proteolytic bacteria resistant to the pasteurization temperature, producing protease by the organisms and finally, changing the product flavour.

Cheese is a fermented milk product with high nutritional value. Traditional cheese has an important role in family meals in Iran and especially in South Khorasan. According to the conditions of production, storage and sale, the possibility of microbial contamination in this product is very high and so it can cause a variety of food borne diseases in consumers. The aim of This Survey was measurement and determination of microbial contamination in traditional cheeses which were marketed in Brijand. For this propose, Brijand city was divided into four regions (North, South, East and West) and 15 samples of traditional cheese were collected from each region (totally 60 samples) under sterile conditions and were studied with standard methods of Iranian national standards organization. Data were analyzed with SPSS software. The statistical analysis of the data showed that the total microbial count (TC) and the rate of contamination with coliforms, staphylococcus aureus and mold and yeast were greater than Iranian standard limits in all samples and also in 93.33% of samples Escherichia coli was isolated. The results obtained in this study concluded that traditional cheese in Brijand has a high microbial contamination and more strict preventive measures are necessary.

This study was carried out to evaluate shelf life, microbiological and chemical attributes of common carp (Cyprinus carpio) fillets treated by dipping in 1.5% lactic acid solution during refrigerated storage at 4oC for 18 days. Mesophilic and psychrophilic counts, TVN (Total Volatile Nitrogen), pH, TBA and Expressible Moisture (EM) were carried out at 0, 3, 6, 9, 12, 15 and 18 days of storage. The microbiological and chemical analyses demonstrated significant reduction in mesophilic and psychrophilic counts, TVN and pH in treatment group (p<0.001). However, TBA (Thiobarbituric Acid) and EM was significantly higher than control group (p<0.001). Shelf life of lactic acid group increased to 12 days instead of 6 days in control group for mesophilic count. For psychrophilic count, it improved from 3 days to 6 days in lactic acid group. TVN acceptability set at 30 mg N/100 g and shelf life of control and lactic acid group were 9 days and 15 days respectively. Acceptability of pH value considered at 6.8-7.0. Control group reached to 7.02 at 15 days of storage and lactic acid group did not reach to 6.8 until the final day. Lactic acid can therefore be used as safe preservative for common carp under refrigerated storage.

Escherichia coli is one of the most important members of coliforms, which are important in terms of Pathogenicity and toxicity. The aim of this study using of Satureja khuzestanica essential oil as an antibiotic and natural preservatives in a food model (cheese UF) was after 60 days of storage. The data was analyzed using SPSS 16 and statistical tests One_Way ANOVA and Repeated Measures Define. The effect of Satureja khuzestanica essential oil (in 0.02% and 0.04% concentration) was studied on Escherichia coli with 104 cfu/ml in retentate consumed for cheese making with the blank sample which was not contained essential oil. The concentration of 0.02 and 0.04 % bacteria in the cheese containing the essential oil of 15 keeping up with the other days showed significant difference with the cheese without Satureja khuzestanica essential oil (p<0.05). And its reduction rate at the end of the storage period in experimental treatments were 2.78 and 2.59 Log more than the blank sample respectively. While the cheese without Satureja khuzestanica essential oil (0%) until the end of the 60 days it still contains more bacteria. Results of determination of pH over a period of 60 days showed significant differences between all treatment groups (p<0.05). These results showed that Satureja khuzestanica essential oil has antimicrobial effects on Escherichia coli in Iranian UF white cheese.

The growing pressure to find new ways for the microbial production of nanoparticles in foods, there is ability to create different shapes and sizes is a wide range of antimicrobial agents. The aim of the present study is to determine the antimicrobial activity of ZnO nanoparticles against at different concentrations strains of Staphylococcus aureus and Escherichia coli on standard and isolated were isolated from food samples. In this experimental study, suspension has been prepared from commercial ZnO nanoparticles in broth medium. After preparing standard strain and the strain were isolated from food samples, was studied using bacteriological tests such as disc diffusion agar methods, minimum inhibitory concentration and minimum bactericidal concentration. According to the results obtained in this study, the maximum diameter of growth inhibition related to the concentration in 5000 mg/ml zinc oxide nanoparticles. The average diameter of growth inhibition of standard strain of E. coli PTCC1399 and S. aureus PTCC11189 respectively were 17.4 and 20.5 mm. The average diameter of the growth of E. coli and S. aureus isolated from foods respectively were 18.4 and 15.4 mm. In terms of sensitivity, Staphylococcus aureus and Escherichia coli, the most had the least effect. Results showed that mean comparison with Duncan test (p˂0.005) is significantly different. Among times, zero time has the highest OD and the lowest OD was obtained in 240 second. Finally, this study showed that ZnO nanoparticles can be used to inhibit mentioned bacteria and can be a potential for alternative preservatives to prevent food spoilage possess.

Butter milk is a dairy, fermented and acidic drink which is a native product of Iran. It is produced by diluting yogurt and adding water and salt to it or through direct fermentation of milk. Among all drinks in markets, butter milk enjoys a special place from the viewpoint of health-giving properties. Among demerits of butter milk, reducing its shelf life and marketability, are change of the flavor and swelling the product by the action of microorganisms. In this paper, the microbial quality of buttermilk, which is made by simultaneous adding the resin of CMC, xanthan and tragacanth, was analyzed during the shelf life. Microbial tests of samples were conducted according to the Iran national standards in order to determine and count the coliforms, Escherichia coli, Staphylococcus aureus, and fungi. The results revealed that adding resin to samples of butter milk increases the stability of the microbial load, but has no effect on pH and organoleptic properties. No contamination to coliforms, Escherichia coli, and Staphylococcus aureus was seen in the samples. The rate of contamination to fungi was in the range of Iran national standard. According to the results, serious actions are necessary to control the fungal contamination of dairy products without using preservatives.

The aim of this study is to introduce processed meat product in the way of minimizing the preservatives substances by using celery powder and barberry juice. In this experiment the production of sausage 55 is designed while substituting the nitrite level of 90, 60, and 0 ppm respectively with level of 1, 2 and 4 percent of celery powder and level of 5 percent the mixture of ascorbic acid and barberry juice. The specifications of produced samples have been analyzed through chemical tests (Thiobarbituric acid, residual nitrite, color analysis, and peroxide values), microbiological analysis and sensory analysis in the 1st and the 21st day of production. The analysis of the sample corresponding with 1 percent celery powder and barberry juice resulted in the averages of 12.63 by red color index, 40.76 by residual nitrite, 4.06 by peroxide values, and 0.183 by thiobarbituric value; closed to the control in compare with other produced samples. Microbiological culture of mold and yeast and enterobacteriaceae within 21days confirmed the quality of substances and materials as well as the appropriate condition of production. Admittedly, taking the texture and color into account, the sense evaluation test shows the average of 4.5, compared to the other produced samples, which was closed to the control. According to the healthly benefits of herbal substances and as claimed by unhealthy specification of synthetic preservatives substances; the outcomes of this study confirms that partial replacement of nitrate with powdered celery and barberry juice, affecting the health value of processed meat product.