| Autor: |
Vandera, Elpiniki, Lianou, Alexandra, Kakouri, Athanasia, Feng, Jinbo, Koukkou, Anna-Irini, Samelis, John |
| Zdroj: |
Journal of Food Protection; January 2017, Vol. 80 Issue: 1 p74-85, 12p |
| Abstrakt: |
Enterococcus faeciumKE82, isolated from traditional Greek Graviera cheese, was identified in pure broth cultures in vitro as a multiple enterocin–producing bacterial strain possessing the structural entA, entB, and entPenterocin genes. E. faeciumKE82 was further assessed for in situ antilisterial activity in raw milk (RM) and commercially thermized milk (TM; 63°C for 30 s) in the presence of the indigenous microbiota and in sterile raw milk (SRM; 121°C for 5 min) with or without the addition of two commercial starter culture (CSC) strains Streptococcus thermophilusand Lactococcus lactis. Growth of Listeria monocytogeneswas completely inhibited in RM incubated at 37°C for 6 h, whereas the pathogen was significantly inactivated in RM+KE82 samples during further incubation at 18°C for 66 h. In contrast, L. monocytogeneslevels increased by approximately 2 log CFU/ml in TM, but in TM+KE82 samples, pathogen growth was retarded during the first 6 h at 37°C followed by growth cessation and partial inactivation at 18°C. After 48 to 72 h, growth of L. monocytogenesin SRM+CSC samples decreased by 4 to 5 log CFU/ml compared with the SRM control, whereas additional 10-fold decreases in the pathogen were observed in SRM+CSC+KE82 samples. Reverse transcription PCR analysis of SRM+KE82 and SRM+CSC+KE82 samples confirmed that the entAand entBgenes were transcribed, but entPgene transcription was not detected. All RM and SRM samples inoculated with E. faeciumKE82 displayed strong in situ inhibitory activity against L. monocytogenesin well diffusion bioassays, whereas activity was weaker to undetectable in comparable or additional TM+KE82 samples; no milk sample without E. faeciumKE82 had activity against L. monocytogenes. The findings of this study indicate that E. faeciumKE82 is an antilisterial agent that could be used in traditional dairy foods because it concomitantly produces enterocins A and B in situ in milk. |
| Databáze: |
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