NOP Compliant Antimicrobial Rinses on Leafy Greens and the Effect on Foodborne Pathogen Indicator Presence

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 2010: $14,944.00
Projected End Date: 12/31/2011
Region: Western
State: Washington
Principal Investigator:
Dan Hulse
Tahoma Farms

Annual Reports


  • Vegetables: greens (leafy)


  • Crop Production: food product quality/safety
  • Education and Training: extension, farmer to farmer, networking, on-farm/ranch research
  • Farm Business Management: risk management
  • Natural Resources/Environment: indicators
  • Production Systems: organic agriculture
  • Soil Management: soil microbiology
  • Sustainable Communities: new business opportunities


    When we commenced the study and our operation was still in its infancy in 2010, there was a belief that our farm was going to have conform to new regulations under the Food Safety Modernization Act (FSMA) that became law in January 2011, and that we were going to have to do so quickly. Part of our response to this was engaging with the faculty at Washington State University (WSU) and, specifically, the food safety team at WSU to develop this grant proposal. Our project was approved in 2010 and our work commenced, as planned, that summer.

    However, our original projections for a timeline turned out to be grossly optimistic: we had a wet, cold growing season that pushed our second round of tests to 2011; our evaluation of the first round of data from the 2010 tests left us feeling ambivalent about the efficacy of our treatments and the design of our study; 2012 was a lost year, at least in terms of the study, as the project got moved further to the back of the burner as other, more pressing farm projects, took precedent; finally, in June of this year, we completed the outreach portion of the project. And, as of the writing of this final report, we are still a couple of weeks out on having the wash basin installed on the farm.

    With that said, the evolution of the project and the delay in implementation of the changes legislated by the FSMA were coincidentally helpful in allowing us to get a better end-product, both in the report presented here and the on-farm solution we came up with.


    Our project set out to test the effectiveness of various antimicrobial treatments in reducing pathogen indicator organisms on leafy greens. The presence of foodborne pathogens in leafy greens has a higher rate of occurrence than any other fruit or vegetable, and with greater regulation of food safety in the fresh fruit and vegetable industry looming, producers need options to help minimize the risk of selling contaminated food. For organic producers in particular, who are prohibited from using chlorine in production or processing, there is a need for a viable alternative to the standard used in many conventional operations that use an antimicrobial rinse. There is not a more critical issue for small- and medium-sized growers right now than that of food safety.

    For this project, heads of leafy greens were assigned to one of six treatments (20 heads per treatment): pre-rinse, water rinse, chlorine antimicrobial rinse, lactic acid rinse, peroxyacetic acid rinse and a vinegar rinse. The pre-rinse treatment will provide an indication of initial microbial load on leafy greens prior to an antimicrobial intervention. After each rinse, heads will be sampled for microbial load to examine the effectiveness of the intervention on reducing indicator organisms. Each head of leafy greens will be enumerated for aerobic plate count (APC) and total coliforms. There were two sampling events for a total test population of 240 heads of lettuce.

    Project objectives:

    Our primary objective was to test the effectiveness of anti-microbial rinses for reducing pathogen indicator organisms on leafy greens.

    Secondary objectives included: designing a wash basin for application of the rinse, comparing the impact on quality and taste of the various applications, and completing an economic analysis to determine the feasibility of each application against the others.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.