Effect of pre-soaking whole pelagic fish in a plant extract on sensory and biochemical changes during subsequent frozen storage

Plant extract treatments have largely shown a positive effect on inhibiting the quality loss during the frozen storage of minced and filleted fish products. In the present case, the effect of a plant extract on a whole fish product was checked. For it, whole fresh horse mackerel was soaked in a commercial extract solution during 60 min and then kept frozen up to 12 months at −20 °C. Sampling was carried out on the initial material and at months 1, 3, 5, 7, 9 and 12. Two parallel experiments consisting on untreated fish (Blank Control) and water treated fish (Water Control) were carried out in the same conditions. Lipid damage was measured by lipolysis development (free fatty acid formation), rancidity development (conjugated dienes (CDs), secondary oxidation compounds, fluorescent compounds and cholesterol oxides) and sensory (odour, firmness and colour) analyses. As a result of the previous plant extract treatment, better odour and colour scores were obtained that led to a larger shelf-life time (7 months) than in the two controls (5 months), according to the sensory analysis. Water treatment of fish (Water Control) also showed some better results in sensory (odour and colour) analysis than the Blank Control, that could be related to the elimination of some prooxidant molecules included in fish. Some biochemical indices (CDs and free fatty acids) also provided a damage inhibition (P<0.05) in the 9-12 months period as a result of the plant treatment and water treatment; however, fluorescence and cholesterol oxide detections did not show differences (P>0.05) when compared to the Blank Control. The present experiment provides promising results for soaking a pelagic whole fish in an aqueous plant extract as a previous step to its commercialization as a frozen product.