Evaluation of antioxidant and antimicrobial properties of ethanolic extract of Watercress on the shelf life of rainbow trout (Oncorhynchus mykiss) fillet at refrigerator temperature

In addition to health effects, plant extracts can be used as natural preservatives with antioxidant and antimicrobial properties in the food industry. In this study, effect of antioxidant and antimicrobial properties of ethanolic extracts of watercress on the chemical and microbial quality of rainbow trout fillet at refrigerator temperature for 12 days was investigated. After drying the leaves at darkness and room temperature extract was extracted with 45, 65, 75 and 96% ethanol solvents for 24 hours at 65 °C. The results showed a significant difference (P≤0.05) in yields and phenolic content, 0.1 mg /ml of extract 65% with an extraction efficiency of 20% the highest amount of total phenol (88.60 ± 2.46%), DPPH (84.73 ± 0%); and ABTS (83.83 ± 0.06%) were. Also, the growth inhibition of the pathogenic bacteria Listeria monocytogenes, Escherichia coli, Staphylococcus aureus and Salmonella enteritidis in sample extracted with 65% ethanol had a significant difference with other extracts (P≤0.05). Rainbow trout fillet samples in 65% ethanol extract showed lower levels of TVB-N, PV and TBA to the control treatment during storage (P≤0.05). Rainbow trout fillet samples in 65% ethanol extract showed lower levels of TVB-N, PV and TBA indices of fillets compared to control treatment during storage (P≤0.05). Talking about bacterial index, the amount of total and pseudomonas bacteria in the treatment containing the extract did not reach the maximum allowable limit (106 cfu /g-1) by the twelfth day, Indicates the effectiveness of the extract on increasing the shelf-life of fillets compared to the control.