Preliminary study of Histamine in Rainbow trout (Oncorhynchus mykiss) samples from fish markets in Tehran

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.