INOVATIVE TECHNOLOGIES FOR SANITIZING AND PRESERVING LOCALLY GROWN PRODUCE

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: TERMINATED
• Funding Source: EVANS-ALLEN
• Reporting Frequency: Annual
• Accession No.: 0223003
• Project No.: VAX-PAO2010
• Project Start Date: Oct 1, 2010
• Project End Date: Sep 30, 2012

Project Director
PAO, S.

Recipient Organization
VIRGINIA STATE UNIVERSITY
(N/A)
PETERSBURG,VA 23803

Performing Department
Agriculture

Non Technical Summary
Fruits and vegetables are susceptible to natural contamination from soil, insects, birds, water, and other sources during growth and harvest. Although most environmental microbes found on raw produce are considered benign, contamination with spoilage microorganisms and human pathogens presents a persistent challenge to the fresh produce industry. Inadequate produce packing, processing, or sanitation can result in further spread of undesirable microorganisms, leading to serious cross-contamination, product damage and/or foodbrone illness outbreaks. Contaminated produce items have caused several large outbreaks of human salmonellosis over the past few years. These outbreaks and related investigation reports suggest persistent field contamination. Further efforts are needed to prevent and reduce produce contamination on farms and throughout the food supply chain. Some produce sanitizing technologies (such as treatments with ozone, chlorine dioxide, bacteriophage, etc.) have been developed recently with claims of effective pathogen reduction. Additional research is needed, however, to validate and/or enhance the efficacy of these technologies to assure produce food safety.

Animal Health Component

(N/A)

Research Effort Categories

Basic

20%

Applied

60%

Developmental

20%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
712	4099	1070	10%
712	5010	1100	40%
712	5299	2000	30%
712	5240	1060	10%
712	7299	1040	10%

Knowledge Area
712 - Protect Food from Contamination by Pathogenic Microorganisms, Parasites, and Naturally Occurring Toxins;

Subject Of Investigation
4099 - Microorganisms, general/other; 5299 - Agricultural supplies, general/other; 5010 - Food; 7299 - Research equipment and methods, general/other; 5240 - Seeds and other plant propagules;

Field Of Science
1070 - Ecology; 1060 - Biology (whole systems); 2000 - Chemistry; 1100 - Bacteriology; 1040 - Molecular biology;

Keywords

produce

fruit

vegetable

food

safety

pathogen

spoilage

Goals / Objectives
The project aims to improve the microbial safety and quality of fresh produce and specialty produce products to benefit producers with limited resources. Research findings will help to identify sources of microbial contaminates in produce products and means to control them. Results will be presented at local and/or national meetings and published in refereed journals for stakeholders to include farmers, producers, students, scientists, extension specialists, etc

Project Methods
Objective One: To development and validate produce sanitizing techniques for small-scale produce packing and food service operations Raw produce (tomatoes, green onions, melons, edamame, etc.) from packing facilities or grocery stores will be inoculated with multiple strains of human and plant pathogens such as Salmonella enterica and Erwinia carotovora to simulate serious field or postharvest contamination. Subsequently the inoculated produce will be washed and sanitized using water containing chlorine dioxide, ozone, organic acids, and/or bacteriophages. Washing systems with and without brushes will be established with various operation time, flow-rate, and agitation or brushing speed. The efficacy of these treatments (applied independently or in combinations) toward pathogen reduction will be measured using selective agar plating and Enzyme Linked Immunosorbent Assay (ELISA). Furthermore, Transmission and Scanning Electron Microscopy will be used to aid interpreting findings of impacts of washing on the removal of pathogens from produce tissues . Objective Two: To development and challenge produce preservation techniques for small-scale produce processing and food preparation Raw produce (tomatoes, green onions, melons, edamame, etc.) from packing facilities or grocery stores will be inoculated with multiple strains of human pathogens such as Salmonella enterica and Escherichia coli to simulate serious field or postharvest contamination. Subsequently the inoculated produce will be sanitized using the methods developed in Objective one and/or dehydrated using an environmental chamber with and without the addition of various preservatives or antimicrobial substances (such as bacteriocins, bacteriophages, etc.) applied either independently or in combinations. The survival and growth of the inoculated pathogens during the process of preservation and product storage with and without refrigeration will be monitored for up to 6 months using selective agar plating and Enzyme Linked Immunological Assay. Surviving strains may be analyzed using Pulsed Field Gel Electrophoresis to understand the influence of contaminant variation (bacterial strains) on the microbial safety and quality of preserved produce items.

Progress 10/01/10 to 09/30/12

Outputs
OUTPUTS: The potential of Salmonella population to rebound on non-washed and washed roma tomatoes and jalapeno peppers in humid storage at 4 degreeC, 10 degree C, 15 degree C, 21 degree C, or 35 degree C for equal or less than 12 days was investigated. The initial inoculation levels of Salmonella on peppers and tomatoes were 5.6 and 5.2 log CFU/cm2, respectively. Air-drying of fruit surfaces resulted in contamination levels of 3.9 and 3.7 log CFU/cm2 on inoculated peppers and tomatoes, respectively. At 21 degree C and 35 degree C, the levels of air-dried Salmonella inoculums on produce surfaces increased equal or greater than 2 log cycles, with the most rapid growth in the first 3 days. Mechanical washing on rollers (rinsing; R-treatment) or revolving brushes (rinsing and brushing; RB-treatment) with water decreased Salmonella counts by equal or greater than 2.5 log CFU/cm2 on both peppers and tomatoes. After R- or RB-treatment, peppers stored at 21 degree C and 35 degree C permitted residual Salmonella (equal or less than 1.4 log CFU/cm2) to grow to 2.6-3.9 log CFU/cm2. During storage, residual Salmonella (equal or less than 1.0 log CFU/cm2) on washed tomatoes increased to 3.1 log CFU/cm2 at 35 degree C following R-treatment and 3.8 log CFU/cm2 at 21 degree C following RB-treatment. Cold storage at 4 degree C and 10 degree C effectively prevented the proliferation of Salmonella on both washed and non-washed produce. The current study on jalapeno peppers and roma tomatoes demonstrated that Salmonella population can rebound on produce in humid storage before or after washing. The finding highlights the benefit of uninterrupted cold storage for safer produce operations. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
The study discovered significant rebound of Salmonella populations on both washed and non-washed fruit surfaces in humid storage. Furthermore the study demonstrated that storage at 10 degree C (or 50 degree F) are adequate for preventing the rebound, whereas leaving washed produce at 21 degree C (or 70 degree F) in humid storage or ripening may erase the decontamination impact from prior washing. The finding highlights the benefit of unbroken cold-chain systems from the farm to the dinner table in produce safety practices, especially under moist storage conditions. The study report was published in a peer reviewed journal to support industry-wide risk assessment and control. Leading produce industry magazines "The Packer" and "Fresh Cut" interviewed the study to generate timely food safety communications for their subscribers and/or viewers worldwide at http://www.thepacker.com/fruit-vegetable-news/Study-shows-safety-bene fits-of-washing-cold-storage-147016525.html and http://freshcut.com/enews/2012/5_MAY_2012/WEB_FC_MAY_2012.html, respectively. Other news groups, including The Grower, Vegetable Grower News, and Food Production Daily, also publicized the study. Two graduate students and eight dietetic interns participated in this laboratory study at VSU to help combat foodborne illness caused by Salmonella. Publications

Publications

• Pao, S., W. Long III, C. Kim, and R. Rafie. 2012. Salmonella population rebound and its prevention on spray washed and non-washed jalapeno peppers and roma tomatoes in humid storage. Foodborne Pathogens and Disease, 9:361-366.

Progress 01/01/11 to 12/31/11

Outputs
OUTPUTS: Produce susceptible to natural contamination from soil, insects, birds, water, and other sources during their growth and harvest. Although most environmental microbes identified on raw produce are considered benign, contamination with human pathogens presents a persistent challenge to the produce industry and public health agencies.Over the past ten years, many multistate outbreaks of salmonellosis associated with various types of tomatoes (e.g., Roma, red, round, and grape) have been reported by state public health departments in the US. Moreover, contaminated green onions were responsible for hepatitis A outbreaks in various states. Investigations of such widespread outbreaks often conclude that contamination likely occurred on the farm or during packing. This study investigated the efficacy of ozone washing appliances for microbial decontamination of tomatoes and green onions. Produce submerged for light or heavy washing in ozone Washer-A or -B (Washer-B generates higher levels of ozone and agitation) or non-ozone Washer-C. Ozone washings reduced total aerobic mesophile counts on whole tomatoes but not green onions when compared to unwashed samples. Washer-B at heavy setting reduced coliform numbers on whole tomatoes by 1.9 CFU/g. Furthermore, Washer-B yielded more than 2.0 log reductions of Escherichia coli (inoculation level at ~6.3 log CFU/g) on the edible portions of tomatoes than Washer-A at comparable settings. A follow-up study using Washer-B showed that ozone application can significantly reduce E. coli and Salmonella in produce wash water to prevent cross-contamination. However, when compared to non-ozone washing of produce, improved reduction of natural and artificially inoculated microorganisms by ozone applications was not found. Microscopic observation corroborates microbial enumeration showing that removing non-edible portions (stem-scars or root-bulbs) of washed tomatoes and green onions is beneficial for microbial decontamination. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Contaminated produce is a major cause of bacterial-related foodborne illnesses in the United States. To meet consumer's demand for safer produce, effective sanitizing methods need to be developed and verified. Ozone washers are marketed to consumers, often through Internet vendors, as home appliances for reducing microbial contaminants in fresh produce. However, limited information is available in literature to verify their effectiveness. Data from this study expands our knowledge of ozone-based kitchen appliances for produce sanitization and their practical value for preventing cross-contamination during produce washing. Furthermore, the findings highlight the importance of removing stem-scar and root bulb portions of washed produce for food safety.

Publications

• Long III, W., S. Pao, P. Inserra, E. Westbrook, and S. Ahn. 2011. Efficacy of ozone washers in reducing natural and artificially inoculated microorganisms on Roma tomatoes and green onions. Journal of Food Safety, 31:268-275.