Use of edible coating of alginate enriched with nettle extract to enhance the shelf life of rainbow trout fillet

The present study was performed to investigate the effect of nettle hydroalcoholic extract (NE) with edible sodium alginate (SA) coating on the quality of rainbow trout fillet (Oncorhynchus mykiss) during a 12-day refrigeration period (4±1˚C). NE was extracted by ethanol solvent and the chemical compounds of NE were determined. Experiments were performed on 4 treatments (T1: control treatment, T2: SA 2%, T3: SA+NE 0.5% and T4: SA+NE 1%) in three replications. The results of chemical tests performed in comparison with the control sample showed that the samples containing the SA and NE were able to control the increase of chemical and microbial parameters (p<0.05). At the end of the storage period, the lowest amount of peroxide value, thiobarbituric acid and total volatile basic nitrogen, and the lowest amounts of lactic acid-producing bacteria, total bacterial count, psychrotrophic values were observed in SA+NE 1% (p<0.05). The results of the sensory evaluation showed that the mentioned treatment maintained the quality of the fillet until the end of the storage period. In general, edible coating of SA with NE can delay the process of lipid oxidation and microbial spoilage and maintain or improve the sensory properties of refrigerated fish fillets.