GENERELLE ASPEKTE Effect of combined application of plant extract and vacuum packaged treatment on the quality of hot smoked rainbow trout Nuray Erkan • S ¸ afak Ulusoy • S ¸. Yasemin Tosun Received: 23 August 2010 / Accepted: 13 January 2011 / Published online: 15 February 2011 Ó Bundesamt fu ¨r Verbraucherschutz und Lebensmittelsicherheit (BVL) 2011 Abstract The effect of plant extract (bay leaf, rose- mary, black cumin seed and lemon oil) treatment on the shelf life of vacuum-packaged fish was studied. Hot smoked rainbow trout was treated with 1 % plant extracts, and their shelf lives were compared with those of control (only vacuum packaged) samples. Samples were stored at 2 °C and sensory evaluation as well as chemical and microbiological analyses were conducted weekly. The control group was spoiled after four weeks of storage. In contrast the addition of plant extracts decreased microbiological activity. The results obtained from this study showed that the shelf life of hot smoked trout stored in cold storage (?2 °C), as determined by overall accept- ability of all data, was 6 weeks for rosemary, black cumin seed, and lemon oil treatment plus vacuum packaged fish and 7 weeks for bay leaf oil treatment plus vacuum packaged smoked fish. Keywords Smoked fish Á Plant extract Á Vacuum packaging Á Shelf life Abbreviations BLO Bay leaf oil RO Rosemary oil BSO Black cumin seed oil LeO Lemon oil TVC Total viable counts PCA Plate count agar TPC Total psychrotrophic count LAB Lactic acid bacteria log cfu Logarithm of colony forming units TVB-N Total volatile basic nitrogen TMA-N Trimethylamine nitrogen TBA Thibarbituric acid 1 Introduction Hot smoked fish is of considerable economic impor- tance worldwide, and particularly in Europe. This foodstuff is produced by a light salting and hot smoking process and is typically consumed as ready- to-eat with no heat treatment. Hot smoked products made from white fish generally keep better than those made from fatty fish (Tu ¨lsner 1994). Given that the shelf life of refrigerated hot smoked fish fillets is relatively short and that there is a growing tendency of consumers for smoked fish, the development of new preservation methods resulting in shelf life extension of smoked fish is required. Vacuum pack- aging (VP) is an effective preservation method for the extension of shelf life of fresh fish and fish products (Lyhs et al. 2001). Plant extracts such as oregano, thyme, bay leaf, garlic and sage have natural anti- microbial and antioxidant properties with the potential to extend the shelf life of foods. Spices and their extracts (essential or nonessential oils and solution) application, in combination with refrigera- tion and frozen (Erkan et al. 2010; Erkan and Bilen 2010), modified atmosphere packaging (Kostaki et al. N. Erkan (&) Á S ¸ . Ulusoy Á S ¸. Y. Tosun Department of Seafood Processing and Quality Control, Faculty of Fisheries, Istanbul University, Ordu cad. No. 200, 34470 Laleli, Istanbul, Turkey e-mail: nurerkan@istanbul.edu.tr J. Verbr. Lebensm. (2011) 6:419–426 DOI 10.1007/s00003-011-0665-8 Journal fu ¨ r Verbraucherschutz und Lebensmittelsicherheit Journal of Consumer Protection and Food Safety 123