WCFS - Western Center for Food Safety

eNewsletter, July 2016




One Health for Food Safety Conference

June 27 - July 22, 2016
Davis, CA

One Health ConferenceEleven faculty representing four vocational colleges in China celebrated the conclusion of an intense 4-week conference for One Health at UC Davis on July 22. The One Health for Food Safety Conference, sponsored by UC Davis Western Institute for Food Safety and Security (WIFSS), provided course participants the opportunity to learn about the connection between the environment, people, and animals. Through classroom lectures presented by UC Davis faculty, and field trips offering hands-on learning experiences, the visiting faculty discovered how they have the power to promote progress towards safer, better quality food systems in China.

Xuzhou Vocational College of Bioengineering, Jiangsu Agri-animal Husbandry Vocational College, Xinjiang Agricultural Vocational Technical College, and Chengdu Agricultural College were represented by faculty with major areas of interest including traditional veterinary medicine, Chinese medicine, food science, bee science, bioengineering, farm products processing and storage, and fermentation engineering.

Robert Atwill, Director of WIFSS, welcomed the group on the opening day and later gave an overview of the programs at WIFSS. At the closing he presented the 11 faculty with certificates of completion. Amanda Arens, Program Manager, Outreach and Training at WIFSS presented an overview of the Web of Causation, illustrating the complex relationships between pathogens and products that can cause contamination. Michael Payne, Dairy Outreach Coordinator, spoke to the faculty about how dairy food safety is managed in the United States and aspects of prudent use of antibiotics in the dairy industry.

Bennie Osburn, Director of Outreach and Training, discussed the approach to developing an overall awareness of food safety issues and summarized the various steps required to address food safety issues from education to regulatory. Heather Johnson, Instructional Systems Designer, WIFSS, discussed vocational education and different teaching methods including problem based learning and blended learning. David Goldenberg, Food Safety and Security Training Coordinator, was instructor for the table top exercises reviewing video segments of potential food safety hazards.  Goldenberg and Johnson facilitated the problem-based learning discussions of the two faculty teams. Michele Jay-Russell, Program Manager for the Western Center for Food Safety and liaison to WIFSS, presented an overview of the relationship of animals and produce.

Osburn, and Chris Brunner, Public Relations Officer with WIFSS, were the conference coordinators. The outreach and training, and research teams, at WIFSS contributed greatly to the success of the conference.












Food Micro 2016

July 19-22, 2016
Dublin, Ireland

Linda HarrisLinda Harris attended the 25th International ICMFH Conference at University College Dublin, Ireland, where she presented a poster entitled Survival of foodborne pathogens in recirculated fungicides applied to fresh-market citrus fruit (Abstract 520).  ‘One Health Meets Food Microbiology’ was the theme of FoodMicro 2016, sponsored by the International Committee on Food Microbiology and Hygiene (ICMFH), and a wide variety of subjects was discussed including food safety, food hygiene, food biotechnology and the application of molecular approaches. The book of abstracts is available here.

















UCCE Marin

UC Cooperative Extension Marin County has posted a website for the Food Safety Workshop series in which Michele Jay-Russell, Alda Pires, and Trevor Suslow participated in June (see June 2016). Included are the speaker presentations, food safety plan worksheets for home use, and other food safety resources.









Southeast Regional Agricultural Water Quality Workshops

July 5-8, 2016

WCFS staff members, Melissa Partyka and Ronald Bond traveled to the Southeast Gulf States of Mississippi and Louisiana to discuss the creation of region-specific agricultural water quality training for FSMA compliance. They established relationships with a number of regional government and extension agents including State Conservationist Kurt Readus of the USDA-NRCS in Jackson, MS,  Bakarat Mahmoud, an Assoc. Extension Professor in Food Safety at Mississippi State University, and Achyut Adhikari, an Asst. Professor and Extension Food Safety Specialist at Louisiana State University in Baton Rouge, LA.  Ronald and Melissa will be coordinating with these individuals and several others from Arkansas and Alabama to conduct at least two workshops in the region this coming fall.






Jackson Meeting

Melissa Partyka












Antaki, E.M., G. Vellidis, C. Harris, P. Aminabadi, K. Levy, and M. Jay-Russell.  2016Low Concentration of Salmonella enterica and Generic Escherichia coli in Farm Ponds and Irrigation Distribution Systems Used for Mixed Produce Production in Southern Georgia.   Foodborne Pathog. Dis.  July 11, 2016, ahead of print. doi:10.1089/fpd.2016.2117.

The purpose of this research was to assess the presence and concentration of Salmonella and generic Escherichia coli in irrigation water from distribution systems in a mixed produce production region of southern Georgia. Water samples were collected during three growing seasons at three farms irrigating crops with surface water (Pond 1, Pond 2) or groundwater (Well) during 2012–2013. Salmonella and generic E. coli populations were monitored by culture and Most Probable Number (MPN).  Salmonella was detected in both ponds in surface and subsurface samples.  It was also detected in center pivot and drip line samples that distributed pond waters.  It was not detected in well pumps or associated drip line water samples.  The overall mean Salmonella concentration for positive water samples was 0.03 MPN/100 mL (range <0.0011–1.8 MPN/100 mL). Nine Salmonella serovars comprising 22 pulsotypes were identified.  Generic E. coli was detected in water from both farm ponds and irrigation distribution systems, but the concentrations met FSMA microbial water quality criteria. The results from this study will allow producers in southern Georgia to better understand how potential pathogens move through irrigation distribution systems.


Davidson, G. R., J. C. Frelka, and L. J. Harris. 2016. Efficacy of peracetic acid-based sprays against microbial loads on conveyors in a walnut hulling facility. Food Prot. Trends 38(4):301-309.

The efficacy of commercial peracetic acid (PAA)-based sanitizer spray applications was evaluated for efficacy in reducing aerobic plate counts (APC) and Escherichia coli/ coliform counts (ECC) on conveyor belts in a commercial walnut huller. Water alone was compared to one of four PAA-based sanitizers at concentrations of 100 or 200 ppm PAA. APC and ECC were significantly (P < 0.05) lower on conveyor belts sprayed with 200 ppm PAA than on those sprayed with water. Significantly (P < 0.05) lower APC and ECC were observed on conveyor belts sprayed with one PAA formulation at 100 ppm (5.00 and 4.14 log CFU/100 cm2, respectively) than on those sprayed with water (6.40 and 6.10 log CFU/100 cm2, respectively). The efficacy of this sanitizer was not significantly different (P > 0.05) at 25, 50, 80, or 100 ppm (APC: 4.32 to 4.51 log CFU/100 cm2; ECC: 2.79 to 2.87 log CFU/100 cm2). PAA sprays reduce microbial levels on conveyer belt surfaces in walnut hulling facilities, which may reduce the potential for cross-contamination.


Frelka, J. C., G. R. Davidson, and L. J. Harris. 2016. Changes in aerobic plate and E. coli-coliform counts and in populations of inoculated foodborne pathogens in inshell walnuts during storage.  J. Food Prot. 79(7):1143-1153.

After harvest, inshell walnuts are dried using low-temperature forced air and are then stored in bins or silos for up to 1 year. To better understand the survival of bacteria on inshell walnuts, aerobic plate counts (APCs) and Escherichia coli/coliform counts (ECCs) were evaluated during commercial storage (10 to 12°C and 63 to 65% relative humidity) over 9 months. APCs decreased by 1.4 to 2.0 log CFU per nut during the first 5 months of storage, and ECCs decreased by 1.3 to 2.2 log CFU per nut in the first month of storage. Through the remaining 4 to 8 months of storage, APCs and ECCs remained unchanged (P > 0.05) or decreased by <0.15 log CFU per nut per month. Similar trends were observed on kernels extracted from the inshell walnuts. APCs and ECCs were consistently and often significantly higher on kernels extracted from visibly broken inshell walnuts than on kernels extracted from visibly intact inshell walnuts. Parameters measured in this study were used to determine the survival of five-strain cocktails of E. coli O157:H7, Listeria monocytogenes, and Salmonella inoculated onto freshly hulled inshell walnuts (∼8 log CFU/g) after simulated commercial drying (10 to 12 h; 40°C) and simulated commercial storage (12 months at 10°C and 65% relative humidity). Populations declined by 2.86, 5.01, and 4.40 log CFU per nut for E. coli O157:H7, L. monocytogenes, and Salmonella, respectively, after drying and during the first 8 days of storage.  For some samples, E. coli or L. monocytogenes populations were below the limit of detection by plating (0.60 log CFU per nut) by day 183 or 148, respectively; at least one of the six samples was positive at each subsequent sampling time by either plating or by enrichment.