Dips and Sanitizers
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Summary of Presentation
Food Safety Session: Ontario Horticultural Crops Conference
February 28, 2002
Presentation Title: Dips and Sanitizers
Presenter: Trevor V. Suslow, Extension Research Specialist. University of CA, Dept. of Vegetable Crops. firstname.lastname@example.org
For producers, handlers, shippers, fresh cut processors, foodservice and retailers of perishable edible horticultural commodities there should be no residual question that prevention and redundant reductions microbial food safety are critical components of a comprehensive product management plan. In addition, while quality and safety are distinct attributes of the marketing of fresh produce, systematic attention to improving microbial food safety has been observed to enhance the quality and the quality of handling of the product. Broader recognition of the potential association of diverse microbial pathogens, from field, packing, or fresh cut processing environments, on fresh produce has been the result of recent multi-state outbreaks and severe episodes of source water contamination. Recent release of import and domestic produce survey data, conducted by the U.S. Food and Drug Administration has highlighted the potential for the acquisition of surface contamination at points from field production to distribution. Of 1003 samples collected, from targeted import commodities, 96% were determined to be free of detectable contamination with Shigella, Salmonella, or E. coli O157:H7, bacterial pathogens associated with outbreaks linked to fresh produce. Forty-four samples were found to harbor detectable populations of either Salmonella or Shigella, with Salmonella being the most common pathogen recovered. Interim results of the domestic survey provide similar insight with the majority, over 98%, of samples being free of detectable target pathogens. However, Salmonella and Shigella were detected on a few samples, which underscore the basic dilemma facing the North American industry. Within the historical and normal modes of operation, the contamination of fresh produce with human pathogens appears to be of low probability but of potentially high consequence. Monitoring and testing for pathogens on perishable horticultural commodities to ensure produce safety is a costly and largely non-informative venture. Improved methods of prevention of environmental contamination and vigilant attention to worker hygiene and sanitary facilities are clearly needed. In conjunction, a better understanding of the performance and limitations of existing produce wash and water disinfection treatments and innovation of new dips and sanitizers for surface and sub-surface contaminants is a clear challenge to the research and development community.
The evaluation of chlorination, chlorine dioxide, acidified sodium chlorite, ozone, active oxidizing radicals from electrolysis, and other various produce washes, dips, and surface sanitizers with and without co-treatments or co-activities (i.e. heat, high pH, low pH, surfactants, brushing, microbial competitors, calcium infusion) has received greater attention in recent years and the results of these tests are being published in great abundance in professional journals and reviews. A capsule overview of all these efforts may be summarized as follows:
- Washing with potable water accomplishes a reduction in surface microbial populations.
- Disinfectants may further reduce microbial populations, primarily on the surface but some may have limited sub-surface activity, particularly in conjunction with co-treatments.
- The range of efficacy of any treatment on a specific commodity or application is broad, from no difference from water alone to a 100 to 1000-fold further reduction.
- Effective doses or treatments may be damaging to the commodity, impractical for the industry, not approved for food use, or present obstacles in worker safety and environmental safety.
- Gaseous or volatile disinfectants can also be efficacious and may provide some sub-surface activity.
- No dip, sanitizer or gaseous treatment may be relied upon or presumed to provide elimination of contamination of produce.
- Natural anatomical, biochemical, and electrochemical features of plant and plant wound surfaces and microbial surface properties are barriers to effective control with all dips and sanitizers tested.
- The difficulty of removal of microbial contamination increases with time of storage.
In the effort to assist the industry in identifying effective products, processes, and methods of removal and disinfection of fresh produce, the research community has been challenged to standardize methods for evaluating and reporting efficacy data. If adopted, the clear benefit will be greater reproducibility and comparability between products and across laboratories. Additionally, better understanding and consistent implementation of systems to monitor, control, and document demand-based disinfectant levels are needed. The ultimate beneficiary will be the industry, which will be able to design and implement Recommended Management Practices with science-based information on performance across multiple options in dips ands sanitizers best suited to the specific application.
Recent Background Literature on Standardization
Beuchat,L., L. Harris, T. Ward, and T. Kajs. 2001. Development of a proposed standard method for assessing the efficacy of fresh produce sanitizers. Journal of Food Protection 64:1103-1109
Beuchat,L., J. Farber, E. Garrett, L. Harris, M. Parish, T. Suslow, and F. Busta. 2001.Standardization of a method to determine the efficacy of sanitizers in inactivating human pathogenic microorganisms on raw fruits and vegetables. Journal of Food Protection 64:1079-1084
Burnett, A. and L. Beuchat. 2001. Comparison of sample preparation methods for recovering Salmonella from raw fruits, vegetables, and herbs. Journal of Food Protection 64: 1459-1465
Suslow, T.V. 2001. Water disinfection: a practical approach to calculating dose values for preharvest and postharvest applications. ANR #7256 and http://vric.ucdavis.edu .
Suslow, T.V. Introduction to ORP as the standard of postharvest
water disinfection monitoring. Electronically available at
|COMMON DISINFECTANT PROPERTIES||CHLORINE GAS||SODIUM OR CALCIUM HYPOCHLORITE||CHLORINE DIOXIDE|
|High||High||High, better than chlorine|
|Specificity||Generally effective, including, viruses; reference sanitizer. Limited practical effect on parasitic spores (i.e. Crytosporidium). Oxidizer and metabolic poison.||Generally effective, including viruses; reference sanitizer. Limited practical effect on parasitic spores (i.e. Crytosporidium). Oxidizer and metabolic poison.||Generally effective. Recognized for biofilm penetration. Oxidizer.|
|Form||Compressed gas. On-site injection.||Concentrated hypochlorite solution or powder||On-site generation from precursors, or sodium chlorate and hypochlorite solutions. Some stabilized forms released on acidification.|
|Stability||Good||Good as powder, fair as liquid||Good|
|Preparation||Easy||Easy||Complex equipment or procedure|
|Measurement||Easy. Functional relation to redox potential (ORP).||Easy. Functional relation to redox potential (ORP).||More difficult. Moderately functional relation to redox potential (ORP).|
|Irritancy||Low||Low||Very irritating vapors|
|Vapors||None at correct pH||None at correct pH||Typical odor, yellow-green, dangerous|
|pH impact||Most active at pH of 6-7.5||Most active at pH of 6-7.5||Effective at broad pH, best at 8.5|
|Temperature||For produce, generally cold water, but heated water up to 52oC in use||For produce, generally cold water, but heated water up to 52oC in use||Use at low temp to minimize vaporization. Some use of gaseous forms on produce.|
|Conc.||25 to 200 ppm||25 to 200 ppm, 20,000 ppm limited approval for sprout seed disinfection||3 to 5 ppm|
|Hard Water||Activity decreases in very hard water(>500 ppm)||Activity decreases in very hard water(>500 ppm)||No effect|
|Organic Matter||Reacts to from chloramines||Reacts to from chloramines||Little influence, even at high organic load|
|Solution Corrosiveness||Slight to moderate||Slight to moderate||Very Corrosive at low pH|
|Corrosive off-gassing||Possible, through condensation||Possible, through condensation||Slight corrosion|
|Other||Very corrosive below pH 6||Very corrosive below pH 6||Vapor space corrosion with high temp.|
|Best use||Food contact surfaces, water disinfection, smooth produce surfaces||Food contact surfaces, water disinfection, smooth produce surfaces||High organic load situations, smooth or complex produce surfaces, flume water disinfection|
|Disadvantages:||Requires tight pH and concentration control; highly corrosive, when improperly used; produces corrosive gas above 46oC.||Requires tight pH and concentration control; highly corrosive, when improperly used; produces corrosive gas above 46oC.||Complex preparation; corrosive in acid solution; very difficult to handle unless preparation is automated|