LAB in minced pork contaminated with Salmonella spp treated with oregano essential oil packaged in vacuum and MAP

Abstract

The survival of lactic acid bacteria (LAB) during 15 days was evaluated in minced pork experimentally contaminated with Salmonella spp. (106 CFU/g) which was treated with different concentrations (0%, 0.3%, 0.6% and 0.9%) of the oregano essential oil (OEO) predominately composed of carvacrol (77.6%), packaged under vacuum or MAP (30%O2/50%CO2/20% N2) and stored at 3 ± 1 °C. Mince was analyzed on day 0 and on days 3, 6, 9, 12 and 15 of storage. At the beginning of the experiment the addition of OEO immediately reduced the number of LAB and their counts ranged between 4.20 (MAP+0.9% OEO) and 4.45 (V) log CFU/g. During the storage period, LAB counts in pork increased by 2.69, 2.50, 1.77, 1.72, 2.81, 2.38, 1.98 and 1.69 log CFU/g in MAP, MAP+0.3%, MAP+0.6%, MAP+0.9%, V, V+0.3%, V+0.6%, V+0.9% samples, respectively. The increase was the most pronounced in the samples without essential oil added and at the end of the study LAB number reached 7.13 log CFU/g in MAP samples and 7.26 log CFU/g in vacuum packaged samples. The most pronounced antibacterial effect was achieved by the combination of MAP and 0.9% OEO where LAB number was 5.92 log CFU/g at the day 15 and vacuum and 0.9% OEO where LAB counts reached 5.93 log CFU/g. pH of the samples at the beginning of the experiment raged between 5.96 and 6.01. Decrease of pH in the samples correlated with increase of LAB counts in the samples and at the end of the storage period was 5.81 and 5.90. Results from the present study indicate that OEO exhibited dose-dependent effect that was stronger during first three days of storage, while the greatest increase of these bacteria was noticed on the day 6 and 9 of storage.

Tokom 15 dana praćen je broj bakterija mlečne kiseline u mlevenom mesu svinja eksperimentalno kontamiranog Salmonella spp (106 CFU/g) u koje su dodate različite koncentracije (0%, 0,3%, 0,6% i 0,9%) etarskog ulja origana (EUO) čija je glavna supstanca bila karvakrol (77.6%). Uzorci mlevenog mesa su pakovani u vakuum (V) ili modifikovanu atmosferu (MAP-30%O2/50%CO2/20%N2) i skladišteni na temperaturi 3 ± 1 °C. Uzorci su analizirani na početku eksperimenta, trećeg, šestog, devetog, dvanaestog i petnaestog dana skladištenja. Na početku eksperimenta dodatak etarskog ulja origana smanjio je broj bakterija mlečne kiseline, a broj ovih bakterija kretao se od 4,20 (MAP+0,9% EUO) do 4,45 (V) log CFU/g. Tokom skladištenja broj bakterija mlečne kiseline povećao se za 2,69, 2,50, 1,77, 1,72, 2,81, 2,38, 1,98 i 1,69 log CFU/g u uzorcima mlevenog mesa pakovanog u MAP, MAP+0,3%, MAP+0,6%, MAP+0,9%, V, V+0,3%, V+0,6%, V+0,9%. Rast ovih bakterija bio je najizraženiji u uzorcima bez dodatka EUO i na kraju eksperimenta dostigao je broj od 7.13 log CFU/g u uzorcima pakovnim u modifikovanu atmosferu i 7.26 log CFU/g u uzorcima pakovanim u vakuum. Najizraženiji antibakteriski efekat postignut je dodatkom 0,9% etarskog ulja origana i broj bakterija mlečne kiseline petnaestog dana skladištenja u uzorcima pakovanim u modifikovanu atmosferu sa dodatkom 0,9% EUO bio je 5,92 log CFU/g, a u uzorcima pakovanim u vakuum sa dodatkom 0,9% EUO bio je 5,93 log CFU/g. pH vrednost na početku eksperimenta kretala se od 5,96 do 6,01. Pad pH vrednosti u uzorcima bio je u korelaciji sa porastom bakterija mlečne kiseline i na kraju skladištenja bila je između 5.81 i 5.90. Rezultati ovog ogleda pokazuju da je antibakterijski efekat EUO dozno zavisan i najizraženiji tokom prva tri dana skladištenja, dok je najveći porast bakterija mlečne kiseline bio zabeležen između šestog i devetog dana skladištenja.