Pathogens found in produce at farmers’ markets

15-Dec-2014 - Last updated on 15-Dec-2014 at 14:13 GMT

Additional studies are needed to determine sources and extent of contamination

Salmonella and E. coli were found in fresh herbs sold at farmers’ markets but the sources and extent of contamination remains unclear, according to a study.

Researchers in Chapman University’s Food Science Program and the University of Washington looked at presence of the pathogens on certain herbs sold at farmers’ markets.

The study focused on farmers’ markets in Los Angeles and Orange counties in California and in the Seattle, Washington, area.

A total of 133 samples (52 basil, 41 cilantro and 40 parsley) were collected from 13 different farmers’ markets between July and October 2013 and tested for Salmonella and generic E. coli.

One sample (parsley) was confirmed positive for Salmonella and 24.1% were positive for generic E. coli, with a range of 0.70–3.15 log CFU/g.

Salmonella findings

Some potential areas of concern at the markets are storage conditions of produce throughout the day, farming practices and the farmers’ pre and postharvest handling techniques, said the study.

For the Salmonella results, of the 133 samples collected, 15 had typical or suspicious growth on HE, XLD and/or BS agars.

However, only one confirmed positive for Salmonella on TSI/LIA and the API 20E test strip.

“The overall prevalence of Salmonella in parsley was 2.5%. The prevalence of Salmonella in fresh herbs found in this study was similar to percentages reported previously for Salmonella in FDA field investigation studies,” said the researchers.

The researchers said although it is not known whether the Salmonella detected was present at infectious levels, contamination of fresh herbs is concerning considering that the herbs are commonly consumed raw.

E.coli results

A total of 16 samples had average E. coli counts considered to be unsatisfactory (≥2 log CFU g−1) according to guidelines by the Public Health Laboratory Service for microbiological quality of ready-to-eat foods.

Basil showed the highest percentage with generic E. coli (26.9%), followed by cilantro (24.4%) and then parsley (20%).

For 12% of samples, the levels of generic E. coli exceeded guidelines from the Public Health Laboratory Service for microbiological quality of ready-to-eat foods.

Samples were collected from 49 different vendors with an average of three per vendor.

Farmers’ markets have been growing in popularity in the US but microbial quality and safety of food sold is unknown, said the researchers.

They added that further research is needed to determine the source(s) of contamination and whether it is greater at farmers’ markets compared with other retail sources of fresh produce.

Source: Journal of the Science of Food and Agriculture

Online ahead of print, DOI: 10.1002/jsfa.6996

“Microbial safety and quality of fresh herbs from Los Angeles, Orange County and Seattle farmers’ markets”

Authors: Donna J Levy, Nicola K Beck, Alexandra L Kossik, Taylor Patti, J Scott Meschke, Melissa Calicchia and Rosalee S Hellberg