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Improving the Efficacy of Sanitizers on Fresh Produce and Produce Processing Surfaces using Electrostatic Sprays

Frank, Joseph; Hurst, William; Hung, Yen-Con
University of Georgia
Start date
End date
The overall objective of the proposed study is to improve the effectiveness of surface sanitation treatments for fresh produce and produce processing surfaces by using electrostatic sprays to provide uniform and effective coverage with minimal chemical usage. Specific objectives are:
  1. To determine the ability of electrostatic sprays of various sanitizing chemicals to uniformly coat various items of fresh produce and produce processing equipment surfaces (stainless steel, Teflon)
  2. To determine the stability of various sanitizing chemicals after being subject to the electrostatic spray process
  3. To determine the ability of chemicals selected on the basis of the first two objectives to inactivate pathogenic microorganisms on the surfaces of fresh produce (Tomatoes, broccoli, cilantro and parsley) using electrostatic sprays
  4. To determine the ability of chemicals selected on the basis of the first two objectives to inactivate pathogenic microorganisms on the surfaces of produce processing equipment using electrostatic sprays
  5. To develop educational and extension programs to disseminate research findings.
More information
NON-TECHNICAL SUMMARY: An IFT/FDA report published in 2001 suggested that different sanitation mitigation strategies are needed for different produce items. An innovative non-thermal method (electrolyzed water) for produce sanitization and food contact surface cleaning will be evaluated through electrostatic sprays to provide uniform and effective coverage with minimal usage.

APPROACH: Sanitizers to be studied will include sodium hypochlorite, a sanitizer which contains peracetic acid, tri-sodium phosphate (TSP), and electrolyzed (EO) water. A spray gun connected to an air compressor will be used to generate electrostatic spray. Sanitizing solutions will be delivered through a disk orifice in the gun sprayer before being sprayed through the nozzle. Properties of sanitizers (pH, ORP, chlorine) will be determined before and after spraying. Fresh produce (tomatoes, broccoli, cilantro and parsley) will be sprayed and the percentage coverage and volume of sanitizer deposited will be measured. Efficacy of different sanitizers immediately after spray and after storage for inactivation of five strain mixture of each of Escherichia coli O157:H7 and Listeria monocytogenes will be conducted. Conditions that maintain the most property of EO water and other sanitizers will be identified and used to inactivate pathogenic microorganisms on the surfaces of fresh produce (Tomatoes, broccoli, cilantro and parsley). The bactericidal effect of the sanitizers (with and without electrostatic charge) on planktonic and attached cells (4 h) and biofilms of L. monocytogenes and Pseudomonas spp will be determined. Research findings will be disseminated through education and extension programs.

PROGRESS: 2004/09 TO 2007/08
The fruit and vegetable industry has experienced a solid growth over the past decade as illustrated by increasing consumption and sales. Although the incidence of foodborne illnesses linked to fresh produce is low compared to foods of animal origin, over the last several years the proportion of foodborne illnesses associated with domestic and imported fresh fruits and vegetables has increased. The microbiological safety of fruits and vegetables requires attention because most fresh produce are consumed raw without undergoing processes, such as cooking, which kill harmful microorganisms. Response surface methodology was used to evaluate electrostatic spray system to maximize solution attachment on the target. Multiple regression yielded models to predict solution attachment as functions of the contributing factors studied (air pressure from 138 to 276 kPa, distance from 80 to 120 cm, and height decrement from 10 to 20 cm), with very high coefficients of determination (R2 = 0.90 and 0.95 for front and back side of the target, respectively) were developed. Within the range of parameters tested, the response predictive model suggested the electrostatic spray system with a 1.50 mm disk orifice size and 7 s spray at 276 kPa air pressure, 10 cm height decrement and 80 cm distance achieved the most efficient solution attachment to the target. The direct application of acidified chlorine based sanitizer was significantly more effective than peroxide based sanitizer with direct (front side of the target) or indirect (back side of the target) application, and more effective than the indirect application of acidified chlorine spray application to inactivate S. montevideo on tomatoes. However, the aerosolized sanitizers had no significant effect in the reduction of the pathogen on cilantro. Additional studies were conducted on peroxide based sanitizer and there was a significant variation in the inactivation rate between direct and indirect of acidified chlorine and within the direct application of acidified chlorine. Overall, electro-statically charged aerosol application had marginal effect in microbial reduction when there was direct application to the inoculated target on tomatoes. An exposure time of five minutes showed significant effect in microbial inactivation on tomatoes when there is direct application of the sanitizer on the inoculated target. The direct aerosol application of peroxyacetic acid with 5 min exposure showed greater than 3 log reduction while the indirect application showing ca. 1 log reduction. The dipping application of peroxyacetic acid was more effective than the aerosolized application with or without electrostatic charge for both tomato and cilantro. The dipping application on tomatoes showed a 6 log reduction in S. montevideo with the 5 min exposure while the aerosolized peroxyacetic acid with and without electrostatic charge showed less than 4 log reduction. On cilantro, the dipping application of peroxyacetic acid reduced S. montevideo by 1.7 log/g while the aerosolized application showed only marginal reductions.

IMPACT: 2004/09 TO 2007/08
This study identified optimal spray conditions for an electrostatic spray system. Since electrostatic applications of chemical sanitizer are equal in effectiveness to non-electrostatic sprays, electrostatic spray has the advantages of less solution volume is required for the process. Results obtained from this study can be used to ensure the safety and quality of selected commodities (tomatoes, broccoli, cilantro and parsley) and hence add value to fresh produce.

Funding Source
Nat'l. Inst. of Food and Agriculture
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Escherichia coli
Bacterial Pathogens
Food Preparation and Handling