Comparative inhibitory effects of Thymus vulgaris L. essential oil against Staphylococcus aureus, Listeria monocytogenes and mesophilic starter co-culture in cheese-mimicking models.
In the present study, we assessed the effects of Thymus vulgaris L. essential oil (TVEO) on Staphylococcus aureus and Listeria monocytogenes, pathogenic bacteria frequently associated with fresh or low-ripened cheeses (e.g., Brazilian coalho cheese), and on a starter co-culture comprising Lactococcus lactis subsp. lactis and L. lactis subsp. cremoris, which are commonly used for the production of different cheeses. To measure these effects, we determined the minimum inhibitory concentration (MIC) and assessed bacterial cell viability over time in (coalho) cheese-based broth and in a semi-solid (coalho) cheese model at 10 °C. The MIC for TVEO was 2.5 μL/mL against S. aureus and L. monocytogenes, while the MIC was 1.25 μL/mL against the starter co-culture. The TVEO (5 and 2.5 μL/mL) sharply reduced the viable counts of all assayed bacteria in cheese broth over 24 h; although, at 5 μL/mL, TVEO more severely affected the viability of the starter co-culture compared with pathogenic bacteria. The addition of 1.25 μL/g of TVEO in the semi-solid cheese model did not reduce the viable counts of all assayed bacteria. At 2.5 μL/g, TVEO slightly decreased the viable counts of S. aureus, L. monocytogenes and Lactococcus spp. in the semi-solid cheese model over 72 h. The final counts of Lactococcus spp. in a semi-solid cheese model containing 2.5 μL/mL TVEO were lower than those of pathogenic bacteria under the same conditions. These results suggest that the doses of TVEO used to control pathogenic bacteria in fermented dairy products, especially in low-ripened cheeses, should be cautiously considered for potential negative effects on the growth and survival of starter cultures.
Laboratory of Food Microbiology, Department of Nutrition, Health Sciences Center, Federal University of Paraíba, João Pessoa, Brazil.
Rayssa Julliane
RJ
de Carvalho
Laboratory of Microbial Process in Microbiology, Department of Food Engineering, Center of Technology, Federal University of Paraíba, João Pessoa, Brazil.
Geanny Targino
GT
de Souza
Laboratory of Microbial Process in Microbiology, Department of Food Engineering, Center of Technology, Federal University of Paraíba, João Pessoa, Brazil.
Vanessa Gonçalves
VG
Honório
Laboratory of Food Microbiology, Department of Nutrition, Health Sciences Center, Federal University of Paraíba, João Pessoa, Brazil.
Jossana Pereira
JP
de Sousa
Laboratory of Food Microbiology, Department of Nutrition, Health Sciences Center, Federal University of Paraíba, João Pessoa, Brazil.
Maria Lúcia
ML
da Conceição
Laboratory of Microbial Process in Microbiology, Department of Food Engineering, Center of Technology, Federal University of Paraíba, João Pessoa, Brazil.
Marciane
M
Maganani
Laboratory of Food Microbiology, Department of Nutrition, Health Sciences Center, Federal University of Paraíba, João Pessoa, Brazil. Electronic address: evandroleitesouza@ccs.ufpb.br.
Evandro Leite
EL
de Souza
D002611:Cheese / Q000382:microbiology*; D018920:Coculture Techniques; D005519:Food Preservation / Q000379:methods*; D008089:Listeria monocytogenes / Q000187:drug effects* / Q000254:growth & development; D009822:Oils, Volatile / Q000494:pharmacology*; D010938:Plant Oils / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000254:growth & development; D046930:Thymus Plant / Q000737:chemistry*
D009822:Oils, Volatile; D010938:Plant Oils
Antimicrobial activity; Low-ripened cheese; Pathogenic bacteria; Technological culture; Thymus