Improving oxidative stability of ready-to-eat shrimp (Metapenaeus stebbingi) by using Tarragon and Savory essential oils at frozen storage

In this study, the effects of Tarragon and Savory essential oils on oxidative stability of ready-to-eat shrimp   (Metapenaeus stebbingi) during three months at frozen storage were investigated. Samples were treated with Tarragon and Savory essential oils and cooked by different cooking methods (frying, oven baking and steaming). Butylated hydroxytoluene (BHT) was used as a reference to compare antioxidant activities. During frozen storage, fat hydrolysis was evaluated through measuring free fatty acid value and oxidation products were measured via peroxide value and thiobarbutiric resistance substance. At the end of storage, the highest amount of free fatty acids (following the control) was observed in steamed savory treated samples (3.2% oleic acid) and the lowest amount in Savory and Ttarragon fried samples (1.11 and 1.75% oleic acid). Following BHT, the lowest amount of peroxide value was obtained from steamed shrimps treated with tarragon (0.92 meq/kg of fat). Also, thiobarbutiric acid values in fried and oven baked samples containing Savory essential oil (0.55 and 0.42 mg MA/kg of fat) was higher than samples containing Tarragon essential oil (0.44 and 0.38 mg MA/kg of fat). The results of the present study indicated that Tarragon and Savory essential oils retarded the oxidation and samples treated with Tarragon essential oil showed slower hydroperoxide and malonaldehyde formation than those of Savory-treated or the untreated samples. The best storage period of the fried, oven baked and steamed products treated with Tarragon and Savory were 1, 2 and 3 months, respectively.