Antimicrobial effect of essential oils of Laurus nobilis L. and Rosmarinus officinallis L. on shelf-life of minced "Maronesa" beef stored under different packaging conditions

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Filipe Monteiro Silva
Gerardo Aguilar
José Almeida
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The aim of this study was to evaluate the effect of essential oils (EOs) of plants naturally occurring in northern Portugal on the spoilage of fresh Maronesa beef burgers stored at 2 and 8 degrees C under different packaging conditions. EOs were obtained from dried leaves of laurel (Laurus Nobilis L.) and rosemary (Rosmarinus officinallis L.) by hydro-distillation using a Clevenger-type apparatus. Analysis of volatile composition of essential oils of rosemary and laurel was achieved by Gas Chromatography-Mass Spectrometry (GC-MS) and Gas Chromatography-Thermal Conductivity Detection (GC-TCD) resulting in the detection of 95.8% and 89.4% of its compounds, respectively. Fresh beef (semitendinosus and semimembranosus) of DOP-Maronesa breed (males; n = 4) were obtained from local market and transported to the laboratory. Samples were stored at 2 and 8 degrees C in two different conditions: aerobiosis (A) and vacuum (V) and analyzed at 0,1, 2, 3, 5, 7,10,14, 21 and 28 days for Lactic acid bacteria (LAB), Enterobacteriaceae, Pseudomonas spp., Fungi, Total mesophilic (TM) and psychrotrophic (TP), color (L*a*b*) and pH. Laurel was the most effective EO keeping pH from increasing. Coordinates L* and a* were higher on samples containing laurel EO for both A and V packaging. Laurel also showed better effect in reducing microbiologic counts in samples packed in A at both 2 and 8 degrees C and packed in V at 8 degrees C. Rosemary was effective in reducing microbial counts on all V samples stored at 2 degrees C. This study allows to conclude that Laurel EO has significant effect in shelf-life, maintaining fresh beef color.