FEB. 18–AMHERST, Mass.–A spice found in most home kitchens proved effective as an antimicrobial agent against Listeria monocytogenes on ready-to-eat meat and poultry, according to a study by the University of Massachusetts-Amherst.

The findings show that “Umass oregano,” the clonal line of oregano developed in the research, offers meat and poultry processors a consistent source of antimicrobial activity. While the “Umass oregano” was tested against commercially available oregano and results were shown to be similar in inhibition against Listeria mono-cytogenes, the Umass clonal line is likely to provide consistency not found in commercially available products.

Ethanol extracts of an elite phenolic phytochemical-producing clonal line of oregano (Origanum vulgare) were used to assess its inhibitory potential against Listeria monocytogenes in both broth and meat systems. The extract was chosen to combat the problem of diverse ingredients among different batches of the same plant species. Thymol and carvacrol, two of the main phenolic constituents of oregano extracts, also were tested in both systems to evaluate their activity against that of the whole oregano extract.

Results indicate that thymol, carvacrol and the clonal oregano line were all effective in inhibiting the growth of Listeria monocytogenes in both broth and meat systems. Researchers found the greatest growth inhibition when the whole oregano extract, which is high in rosmarinic acid, was used in meat systems. In meat systems, 800 ppm of the oregano extract significantly inhibited the growth of the pathogen, and this was shown to be more effective than just the phenolic extracts tested separately. From these studies it appears that one of the keys to effectiveness is the ability of the compound to be active at the interface of the lipid – water phase of the meat matrix.

“The results of this study are very promising for the ready-to-eat meat and poultry industry – and other sectors of the food industry that are seeking to control Listeria monocytogenes through the use of natural ingredients,” according James H. Hodges, president of AMI Foundation, the principle sponsor of the research work.

Hodges notes that UMass researchers have developed a highly consistent and reliable natural source of antimicrobial activity for further study and evaluation.