Effects of different plant (Marjoram and Olive leaf) extracts on quality characteristics of red and ordinary muscles of vacuum–packaged tuna–like fillets

Abstract

A comparative study on the effects of marjoram (ME) and olive leaf (OLE) extracts on the quality parameters of red and ordinary muscles of tuna–like fillets kept under vacuum–packaging at refrigerated storage were investigated in this study. Tuna–like (Auxis thazard) fillets were dipped in sterile plant extract solutions (0.5% w/v) for five minutes and vacuum–packaged. Chemical, microbiological, and sensory assessments were performed on each of the muscles throughout the 18 days of the refrigerated storage. Several quality indices were significantly lower (P < 0.05) in ordinary muscle than in red muscle. However, the quality parameters of both muscles had the same tendency and were significantly affected by time as well as by the applications of plant extracts. Sensory assessments showed that both muscles from tuna–like fillets had 12 days of shelf–life, while OLE and ME applications extended significantly (P < 0.05) the shelf–life of both muscles for 3 and 6 more days, respectively. Microbiological analyses and total volatile base–nitrogen (TVB–N) assessment revealed a longer shelf–life for all samples, whilst thiobarbituric acid reactive substances (TBA) analysis suggested that vacuum–packaging alone was sufficient to delay lipid oxidation of fish fillets, especially on dark muscle. However, the application of ME was more effective in prolonging the shelf–life of vacuum–packaged tuna–like fillets. Thus, the employment of OLE or ME improved the quality parameters of fillets throughout the experiment and can be used by the fish processing industry.