sona kalteh

Listeria monocytogenes is a gram-positive and foodborne pathogen that is psychrophilic and has the ability to tolerate a high percentage of salt by more than 10%. This bacterium grows in many food products that have a long shelf life. This study was performed to evaluate the expression of genes hly and inlA of Listeria monocytogenes bacteria in the viable but non-culturable (VBNC) condition in temperatures of 4 degrees Celsius.

In this descriptive laboratory study, bacteria in 106 counts in mid log phase were inoculated into BHI Agar rich medium and It was investigated and stored at refrigerated temperature (4 degrees Celsius) until the cultivate was lost. At the end of the 16S rRNA gene, the hly and inlA genes were studied as pathogenic genes of this bacterium. The expression of these genes before and after entering to VBNC state was performed to compare their expression.

Listeria bacteria lost its cultivation ability after 5 months of storage at a refrigerated temperature. The results of the gene expression analysis showed that at the end of the period, the bacterium entered "Viable But non-Culturable" form; also the hly and inlA pathogenic genes were not expressed in riched medium. By adding blood to the rich culture medium of this bacterium, the hemolysin O pathogen gene was re-illuminated.

The results of this study show that the possibility of bacterial entry into VBNC mode occurs at the refrigerator condition, and the expression of its pathogenic genes is affected. Blood and its agents can act as an agent for the induction and clarification of the hly gene. Therefore, it is necessary to review the microbial quality control of fishery products.

The purpose of this study was to investigate the possibility of Listeria monocytogenes entering the VBNC state during the frozen storage and the expression of its pathogenic genes Bacteria in 106 Colony counts of in mid log phase were inoculated into three Culture medium including Normal Saline (NS), BHI Broth and Fish Broth (FB) and kept at -18ºCfor 2 months and examined. Then, bacteria were evaluated on enriched medium BHI agar using culture methods (colony count) over times 4 and 8 hours, 2, 4, 8, 20, 30 and 60 days after the freezing shock using the method of RT-PCR for investigating the expression of 16S rRNA, hly and inlA genes; they were evaluated before and after the freezing shock. This bacterium retained its ability to cultivate until the end of the shock, but reduced its number. Freezing stopped the expression of genes of hly and inlA, as these genes were not expressed in a rich culture medium either. By adding blood to the rich culture medium of this bacterium, only the hemolysin O pathogen gene was expressed. Although freezing does not lead to the introduction of this bacterium into the VBNC state, it is effective as an adverse environmental factor for the bacteria in the expression of its pathogenic genes. Blood and its agents can act as an agent for the induction and clarification of the hly gene, and the expression of pathogenic bacterial genes are independent of each other.

The purpose of this study was to investigate the effect of different methods of preparation of raw rainbow trout (Oncorhynchus mykis) (full, empty stomach, fillets and fillets of butterflies) on quality and shelf life was over 4 months of storage in home freezers. To this end, rainbow trout transferred to the laboratory and washed, were prepared by the method described and qualitative assessment of fish at the end of each month by measurement of chemical parameters (free fatty acids, thiobarbituric acid, protein, fat, moisture, ash, under pressure moisture, pH, heme iron content) and sensory (flavour, odor, texture, color) were performed. With increasing storage time heme iron content reduced, so that at the end of storage heme iron content was more in treatment of whole fish. Also under pressure moisture, TBA nad FFA increased in different treatments and in the fourth month of storage, the rate of these variables were lower in treatments of whole fish. Sensory analysis results indicate utility of all treatments decreased with increasing storage time but the rate of decline was less than in whole fish. According to the results, as can be fish kept in perfect shape than in other forms it is recommended.

The aim of this study was to evaluate the effect of edible gelatin coating on the quality characteristics and shelf life of fish finger of Hypophthalmichthys molitrix during refrigerated storage. Fish fingers were immersed in coating solutions of gelatin 4% and then dried, packed and stored in refrigerator (4˚C). Chemical (moisture, protein, fat, ash, pH, PV, TBA and TVB-N) and microbial parameters (TVC and PTC) were measured at 0, 3, 6, 9, 12, 15, 18 and 21 days. According to the obtained results by increasing of storage time moisture and fat content decreased and pH value were significantly increased (P < 0.05). While there was no significant difference between the ash content of control and coated samples (P < 0.05). Peroxide value and thiobarbitoric acid of coated samples were lower than the control. The TVB-N value of control and coated samples were 27.80 and 27.46 mg N/100g of flesh fish in 12 days of storage that higher than acceptable value. The total viable count (TVC) and psychrotrophic count (PTC) of fish fingers were significantly increased (P < 0.05) during refrigerated storage. The results of this research indicate that the gelatin coating reduces the oxidation, but has no effect in reducing the value of microbial count.