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Devon Zagory, Ph.D.
Senior Vice President for Food Safety & Quality Programs Food Safety & Quality Programs, Davis Fresh Technologies, LLC
From: University Of California, Davis Food Processors Sanitation Workshop
Because fresh-cut fruits and vegetables are living and breathing during and after processing, they are subject to rapid deterioration and can support the growth of large populations of microorganisms. Unlike other processed foods, there is no kill step during processing and there is no treatment, other than good temperature management, that will significantly retard deterioration. Thus, the retardation of deterioration and microbial growth is one of the principal challenges facing fresh-cut processors. Because product deterioration is the result of many ongoing biochemical and microbiological processes, no single treatment will stop them all. Maintaining the quality and safety of fresh-cut produce is a challenge that is only met by doing many small things well. If temperature is not managed well, good sanitation and adherence to Good Manufacturing Practices (GMP's) will not ensure either quality or safety. A poor sanitation program will prevent HACCP from functioning fully.
Good sanitation and food safety are best provided through the proper use of multiple programs, including GMP's, sanitation programs, QA (quality assurance) and HACCP (Hazard Analysis Critical Control Point) programs. Each rests upon the other and will not work well unless the supporting program is in place.
Because fresh-cut produce is prepared from a raw agricultural product produced in contact with soil, often eaten raw, and with no processing kill step to ensure microbiological safety, there are particular concerns of food safety not encountered with retorted or frozen foods. Human pathogens can and do infest fresh fruits and vegetables and have been responsible for food borne illness. Processing these products can take a point source of bacterial contamination and disseminate it throughout a batch of product. Conditions inside flexible plastic packages (high humidity, low oxygen and high carbon dioxide) can encourage growth of pathogens that might not otherwise thrive on produce. If these packages then encounter temperature abuse, pathogens may grow and cause problems. While each of these may be low probability events, their possibility requires prudent processors to take them very seriously.
Good sanitation practices should focus on those places and practices where contamination of food is most likely. Contamination with pathogens is most likely to occur from:
Foodborne Illness Outbreaks Associated With Fresh Produce In The United States, 1986-1996
|
Year |
Commodity |
Microorganism |
# of Out-breaks |
Source of Contamination |
| 1986 | Fruit salad Lettuce |
Giardia lamblia Shigella |
1 2 |
Pet rabbit in home Undetermined |
| 1987 | Lettuce Shredded cabbage |
Shigella Clostridium botulinum |
1 1 |
Infected food handler Field contaminated, temp. abused in MAP |
| 1988 | Tofu salad Iceberg lettuce |
Shigella Hepatitis A |
1 1 |
Infected food handlers Suspected contamination from infected food handler |
| 1989 | Cantaloupe, honeydew and pineapple Garlic in oil Cantaloupe |
Campylobacter Clostridium botulinum Salmonella chester |
1 1 1 |
Food handler in restaurant cut fruit and raw meat on same surface Field contaminated Field contaminated fruit from Mexico |
| 1990 | Tomatoes Cantaloupe Raw vegetables Salad bar |
Salmonella Salmonella Giardia lamblia Salmonella montevideo |
1 1 1 1 |
Undetermined Field contaminated Infected food handler sliced vegetables Cross contaminated from uncooked meat in restaurant kitchen |
| 1991 | Cantaloupe Watermelon Apple cider |
Salmonella poona Salmonella javiana E. coli O157:H7 |
1 1 1 |
Field contaminated Field contaminated Field contaminated |
| 1992 | ||||
| 1993 | Tomatoes Melons |
Salmonella E. coli O157:H7 |
1 1 |
Undetermined Cross contaminated from raw meat by food handler |
| 1994 | Scallions Salad bar |
Shigella E. coli O157:H7 |
1 1 |
Speculated that nonpotable rinse water was used Cross contaminated from raw meat |
| 1995 | Alfalfa sprouts Iceberg lettuce (Maine) Iceberg lettuce (Idaho) Leaf lettuce (Montana) |
Salmonella E. coli O157:H7 E. coli O157:H7 E. coli O157:H7 |
1 1 1 1 |
Undetermined Cross contamination at point of preparation with raw meat Cross contamination at point of preparation with raw meat Speculate surface water or unsanitary handling practices at grocery store. |
| 1996 | Sprouts Raspberries Mesclun salad |
Salmonella sps. Cyclospora E. coli O157:H7 |
1 1 1 |
Undetermined Water used for pesticide spray mix carried the parasite Suspected poor sanitation at the processor |
Number of outbreaks ascribed to fruits and vegetables where contributing factors were known:
|
No. or % of Outbreaks Where Factors Were Reported |
Improper Temps. |
Inadequate Cooking |
Contaminated Equipment |
Food From Unsafe Source |
Poor Personal Hygiene |
|
67 |
40 |
55 |
25 |
17 |
29 |
|
% |
60 |
82 |
37 |
25 |
43 |
J. Food Prot. 53(9):804-817. 1990
As can be seen from the proceeding tables, most food borne illness associated with fresh fruits and vegetables in the United States has been due to contamination of raw product in the field or from food handlers in processing facilities or restaurants. This does not imply that sanitation measures in produce processing facilities are not important. Rather that additional effort needs to be placed on sanitation in production areas and hygiene and training of food service workers.
Since sterilization of product or remediation of contaminated product is not possible, prevention of contamination is the only option for ensuring food safety. Some issues and methods will be briefly discussed here. A more complete treatment of these and other produce safety issues can be found in the Food Safety Guidelines for the Fresh-cut Produce Industry, available by joining the International Fresh-cut Produce Association, 800-452-6552. All businesses involved in fresh-cut produce processing should become members of this association to gain access to a wealth of technical information on processing and safety issues.
Field Sanitation Issues
It is clear from the above points of possible contamination that produce sanitation must start in the field and encompass all areas of growing, harvesting, handling and processing. While many processors have little influence over how and where raw product is produced, all should take an active role in making their sanitation and safety concerns known to their suppliers and to find alternate suppliers when those concerns are not addressed. One approach is to request that growers provide evidence and documentation of the microbiological safety of their fertilizers, irrigation water and worker hygienic practices. A sample letter requesting such information may take the following format:
As Fresh-Cut Produce processors, we strive to provide the best quality and safest product possible. As with all food providers, the safety of our products is of paramount concern to us. Certain elements of that safety reside with you, our supplier. We are sending this letter to make you aware of our concerns and to help you provide us with assurances and documentation that you are taking steps to ensure the safety of the ingredients that you are supplying to us.
Our concerns are in three areas: Pesticide use and documentation, fertilizer use and documentation and irrigation water quality and documentation. We would like assurances from you that you have the following programs:
Pesticide Control Program
- Maintain specification sheets for all agricultural chemicals applied to crops.
- Material Data Safety Sheets (MSDS) must be made available for all agricultural chemicals applied to crops.
- All chemicals applied to crops are EPA approved for their respective applications.
- Evidence of pesticide applicators license(s) and training documentation for all workers applying pesticides.
- Complete records of all pesticide applications.
- Documentation of reviews to assure legal compliance and proper application of all pesticides.
- Documentation of proper storage of pesticides.
Fertilizer Control Program
- No manure used as fertilizer.
- No sewage sludge used as fertilizer.
- Crops not grown on land that has been used for grazing livestock in the previous two years.
- Specification sheets for all approved fertilizers, identifying the composition and the intended use of the fertilizer.
- Material Safety Data Sheets (MSDS) for all fertilizers.
- Documentation of proper storage of fertilizers.
- Records of all fertilizer applications.
- Analysis of all fertilizers to confirm that they do not contain excessive levels of heavy metals.
Water Quality
- Analysis of irrigation water quality, including levels of E. coli and heavy metals.
- Documentation that well water, if used, meets EPA guidelines.
- Records of any chemical treatments of irrigation water.
We believe that it would be in both of our interests for you to maintain such documentation. These assurances of safety are very important to us, as they are important to all Fresh-Cut Produce processors. In the future these concerns are likely to become even more important and, indeed, any grower wanting to sell raw product to processors will almost certainly need to maintain such records.
Please respond to this letter in writing informing us of your safety programs and documentation. Together we can work to ensure the safety and wholesomeness of all of our products. Thank you for your cooperation.
Working with suppliers to maintain such documentation can help ensure safe raw product and is an essential part of a good HACCP program. In addition, growers should certify that field workers and harvest crews have access to, and use, toilets and hand washing stations. While these are commonly available (and required) in the United States, off shore producers should be held to the same standards of hygiene.
Worker Hygiene
Similarly, within the processing plant, workers hands can be contaminated with pathogens. All personnel that contact product should be required to wear gloves and to use hand dips (usually iodine or quaternary ammonium solutions) before being allowed on the processing floor. These requirements should apply equally to workers, management, maintenance workers and visitors. Neither gloves nor smocks should ever be worn into bathrooms. Signs stating that workers must wash hands with soap and water after using the bathrooms should be posted in appropriate languages. Worker hygiene training programs should reinforce the importance of hand washing by explaining the reasons for hygiene and the consequences of poor hygiene. These practices are included in GMP's, sanitation programs and as part of HACCP.
Processing Facility Sanitation
Wash Water Sanitation. Product wash water, if not properly sanitized, can become a source of microbiological contamination for every piece of product that passes through. It is a widespread misconception that chlorinated wash water cleans and/or sterilizes produce as it is washed. Chlorinated wash water does little more to clean produce than clean, non-chlorinated water. Chlorine does sanitize the wash water and maintains a low microbiological count in the water. In this way the water does not become a reservoir for bacteria to infest the produce. Sodium (or sometimes calcium) hypochlorite is most commonly used in produce wash water. The antimicrobial activity of these compounds depends on the amount of hypochlorous acid (HOCl) formed. This, in turn, depends on the pH of the water, the amount of organic material in the water and, to some degree, the temperature of the water. Above pH 7.5 very little chlorine occurs as active hypochlorous acid, but rather as inactive hypochlorite (OCl-). Therefore, the pH of the water should be kept between 6.0 and 7.5 to ensure chlorine activity.
Organic material in the water will reduce the activity of chlorine so periodically replacing or filtering the water is important to maintain cleanliness.
Alternatives to hypochlorite are available for produce water disinfestation. Chlorine dioxide is not approved for use on cut produce but can be used in wash water or in contact with intact produce. Chlorine dioxide is less sensitive to pH and organic mater than is hypochlorite and is active at lower concentrations. Chlorine dioxide generation systems are generally more expensive than hypochlorite. Sodium hypobromite (bromine based) is also approved for use in place of sodium hypochlorite but I am not aware of any use of bromine for water sanitation in the produce industry. Ultraviolet light systems are available for water sterilization as well as for use on produce surfaces. Ultraviolet light leaves no chemical residues and is not affected by water chemistry. However, it is only surface active and so requires clear water to be effective. Ozone is approved for use as a water sterilant but not for use directly on product. Ozone is a very good sterilant but is subject to environmental and worker exposure regulations.
Activities and environmental sensitivities of wash water sanitizers.
|
pH |
Organic Matter |
Biocidal Activity |
|
|
Hypochlorites |
6.0-7.5 |
Very sensitive |
Oxidizer |
|
Chlorine dioxide |
6.0-10.0 |
Sensitive |
Oxidizer |
|
Ozone |
6.0-8.0 |
Somewhat sensitive |
Oxidizer |
|
Peroxyacetic acid |
1.0-8.0 |
Somewhat sensitive |
Oxidizer |
|
UV light |
Not affected |
Somewhat sensitive |
Disrupts DNA |
Facility Sanitation. Cleanliness of all work surfaces and equipment is an important quality assurance and product shelf life issue. Product infested with high populations of bacteria is likely to become decayed and/or slimy sooner than similarly handled cleaner product. However, the chief environmental safety issue is probably the possible presence of the bacterium Listeria monocytogenes within the processing facility. Listeria is a common environmental contaminant that thrives in cold, wet environments such as those encountered in fresh-cut processing facilities. Once established, Listeria can be difficult to eliminate and constant sanitation and testing are necessary to prevent its establishment. Listeria is most likely to be found in drains, refrigeration drip pans and any place where cold water accumulates and stands. A comprehensive environmental sanitation program may include specific swab tests for Listeria and vigorous sanitation of all areas where Listeria is likely to be found. Again, prevention is the best defense against disaster.
Specific recommendations for sanitizing compounds, their proper application and sanitation schedules can be found in the IFPA Food Safety Guidelines.
HACCP
Hazard Analysis Critical Control Point programs are designed to prevent chemical, physical and microbiological hazards in the processing of foods. HACCP is not a quality assurance program and should be operated separately from the QA program. However, HACCP can only function properly along with the proper implementation and enforcement of GMP's and a comprehensive sanitation and QA program. Once these are in place, HACCP can be introduced.
HACCP is a highly structured program that depends on identifying possible hazards and preventing them through proactive measures and constant monitoring and documentation. When done properly, it is the best method for preventing food borne illness due to consumption of fresh-cut produce. The seven steps of HACCP are as follows:
Clearly HACCP is a multilevel system that requires substantial commitment from management and workers to operate effectively. When done well, HACCP is a powerful tool to assure food safety.
Sanitary Plant Design. A poorly designed facility may be nearly impossible to keep clean. Inaccessible spaces, overhead members, immovable equipment and poor drainage make sanitation a very difficult proposition. Attention to sanitation during the design process can save time and resources and prevent problems later. For example, all exposed pipes, wires and drainage lines should be at least two inches away from walls and ceilings to allow access for cleaning and sanitizing. All drains should have removable grates over them for easy cleaning and sanitizing. Motors should not be mounted over produce handling areas. All equipment should be installed at least 6 inches above the flow to allow for access from beneath.
Consulting firms are available to aid in sanitary design as are several printed resources. Once again, prevention of unsanitary conditions is the best strategy to avoid problems.
Resources
Current Good Manufacturing Practice (CGMP) regulations. The regulations are current through February, 1994. The CGMP regulations are issued under Title 21, Code of Federal Regulations, Part 110 (21 CFR 110). Amendments to the regulations appear in the Federal Register. You may subscribe to the Federal Register or order 21 CFR 100-169 by submitting the current cost by check or money order to: SUPERINTENDENT OF DOCUMENTS, U.S. GOVERNMENT PRINTING OFFICE, WASHINGTON, D.C. 20402, or by telephoning the Government Printing Office at 202-783-3238 to charge on Visa (copyrighted) or Mastercard (copyrighted).
"Guidance for Industry: Guide to Minimize Microbial Food Safety Hazards for Fresh Fruits and Vegetables." Additional copies are available from: Food Safety Initiative Staff, HFS-32, U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, 200 C Street S.W. Washington, DC 20204. (Tel) 202-260-8920. (Internet) http://www.fda.gov
References
Sanitation Handbook. 1970. USDA-CMS. Washington, D.C.
J.A. Troller. 1983. Sanitation in Food Processing. Academic Press. New York.
D. Zagory & W. C. Hurst (Eds.). 1996. Food Safety Guidelines for the Fresh-cut Produce Industry. Third Edition. IFPA, Alexandria, VA.
