The effect of Pre-slaughtering injection of Marjoram extract (Origanum Spp.) on the quality of rainbow trout fillets stored in the refrigerator (4 ° C)

Document Type : Research Paper


1 Department of Fisheries

2 Deapartment of Fisheries


Synthetic preservatives have been used in the food industry for many years. However, studies have shown that some of the synthetic preservatives can be dangerous for human health. Therefore, research on natural alternatives attracted more attention, recently.The purpose of this study was to evaluate the preservative effect of Marjoram extract at different concentrations (0 (control), 3, 6 and 9%) for injection before slaughtering the rainbow trout fillet during the refrigerated storage. Thus, 2 ml of blood was drawn from live fish and immediately 2 ml of each concentration of Marjoram extract injected to the live fish. Approximately, 30 minutes after injection, the fish were slaughtered (out of water), and then the fillets were refrigerated for 16 days. The quality of samples was determined by testing the pH, spoilage microorganisms and secondary lipid oxidation, Hem iron and total volatile nitrogen compounds on days 1, 4, 7, 10, 13 and 16 of storage. The results showed that pre-slaughter injection of Marjoram extract significantly effects on the survival of treated fish. Also, severity of spoilage of the treated fish was reduced (p<0.05). The results of thiobarbituric acid index and the index of nitrogen compounds, indicated that the Marjoram extract was able to delay the lipid oxidation and decomposition of protein synthesis in rainbow trout fillets. Therefore, application of marjoram extract at 9% for survival of rainbow trout fillets is recommended.