The effect of packaging method on the shelf-life of gravad rainbow trout (Oncorhynchus mykiss)

In this study gravad, a minimally processed product, made from rainbow trout was investigated in order to establish its shelf-life under different storage conditions. Trout fillets rubbed with 1:2 mixture of salt and sugar in the amount of 350 g kg(-1) of raw material, and matured for 48 It at 3 degrees C were then packaged in vacuum, ambient air and two different modified atmospheres (15% N-2, 25% O-2, 60% CO2 and 40% N2, 60% CO2) and stored for 12 weeks at 3 degrees C. In addition, a vacuum packaged product was stored for 24 weeks at -30 degrees C and the effect of storage on quality was investigated. Sensory and microbiological analyses were performed as well as amino nitrogen content, the thiobarbituric acid (TBA) value and acidity (pH) were determined. It was shown that the changes in lipid fraction are mainly responsible for limited storage stability of the product. Vacuum packing proved to be the best method of chilled storage, where the shelf-life was 8 weeks, although frozen storage of vacuum packed gravad exceeds 6 months without substantial, negative changes in sensory attributes.