The use of Lactic Acid Bacteria metabolites (nisin and organic acids) for the shelf life extension of trout (Oncorhynchus mykiss) and their,s effect on dominant bacteria in inoculation study

Nisin is a natural antimicrobial and has inhibitory effect on the pathogens and spoilage organisms. The efficiency of nisin reduced after reaction with food compounds. There is the hypothesis that combination of nisin with organic salt increases the shelf life of fish. The purpose of this study was mainly to evaluate the effects of nisin (0.15 %) and sodium acetate ( 1% ) individually and in combination on shelf life of fillets and whole trout ( without viscera). then, the behavior of Listeria monocytogenes and Clostridium botulinum type E were evaluated in different time at 40C. Physical and chemical parameters including: pH, Peroxide Value (PV), Tiobarbithoric Acid (TBA) and Total Volatile Nitrogen (TVN) and bacterial factors such as Total Viable Count (TVC), Pscycrothophic Count (PTC) and Lactic Acid Bacteria (LAB) were examined. These parameters were done at intervals of 4 days for 16 days. Results showed that chemical and bacterial factors of whole trout (Oncorhynchus mykiss) ( (without viscera) have been more favorable than the fillets . It also showed that the peroxide value , the thiobarbituric acid, volatile nitrogen bases , and pH in combination of sodium acetate and nisin Z treatments were exposed to significantly compared to control treatments ( no preservatives ) (P<0.05). Treatments with sodium acetate and nisin Z (individual ) were exist after combination treatment. Hence it can be concluded that the maximum shelf life of in preservative treatments was 16 days , but control treatment was 12 days in some cases and in some cases 16 days. Effects of treatments on Listeria monocytogenes and Clostridium botulinum in the control treatment showed the highest growth was observed in both species ( log 8 ) but in single and combined treatment of bacterial growth slower , but is still the trend the 16th day of so Listeria and Clostridium log 5 to log 6 , respectively. Vegetative cells of Clostridium were more sensitive in compare to Listeria. When using preservatives (chemical or biological) in fish tissue, parameters such as the type of preservative, used method, pH, proteolytic enzymes, the incidence of resistant strains and so on influence of antimicrobial agents used. The overall conclusion of the study was shelf life of whole trout (without viscera) was more than fillets, combination of nisin and sodium acetate were better than other treatment and finally higher doses of bilogival preservatives are need to for achieve to significant reduction of pathogenic bacteria .