Gordon Johnson, Extension Ag Agent, Kent Co.; gcjohn@udel.edu
Salmonella related illnesses traced to fresh tomatoes have been in the news. This has prompted increased scrutiny of the safety of fresh fruits and vegetables. The suspected cause of the recent outbreak is contaminated wash water and the temperature of the wash water in packing plants. Salmonella (and other foodborne illness causing pathogens, such as E. coli) can enter produce, such as tomatoes under certain temperature conditions related to the produce and the wash water. According to the FDA, “The temperature of the wash water should be 10 degrees Farenheit warmer than the tomato temperature to prevent infiltration. Cold water causes air cells in the tomato to contract and create a vacuum drawing water into the tomato.” While we do not have any large tomato packers in Delaware, growers large and small should still be aware of ways to reduce the risk of contamination of fresh produce. Some key considerations:
● Manures and animal feces/droppings are a major source of contamination – make all efforts to avoid any contact between raw manures or animal wastes with produce.
● Irrigation water can be a source of contamination, especially ponds and streams. Well contamination is less likely, but is possible. Test irrigation sources for Coliform bacteria. Make efforts to eliminate animal access or other contamination of these water sources. Overhead irrigation is more likely a source of contamination than drip irrigation.
● Most pathogens harmful to humans are carried by other animals (fowl; reptiles; amphibians; mammals, such as dogs, cats, deer, raccoons, etc). Exclude as many animals as possible from the fields.
● Any animal materials (waste, carcasses, etc.) should be removed immediately from the field if possible (and practical).
● Workers who come in contact with live animals, animal carcasses, or animal waste materials should wash their hands before they continue working.
● Animal manure applied as fertilizer should not be applied to fields any less than 90 days before harvest for produce not in contact with the soil. Manure must be incorporated. Otherwise, manures should be composted before use to kill pathogens. Be aware of land use near the field. Avoid establishing fields near animal operations or waste handling facilities.
● Produce that falls to the ground should not be harvested for fresh market.
● Minimize animal contact in packing facilities or areas where produce is handled or stored and where produce handling equipment is stored.
● Cull out vegetables showing bruises or decay symptoms as a preventive measure. Ideally, harvest workers should not handle culls. Culls should be removed by a separate worker, if possible, so as not to contaminate sound produce.
● Containers used in the field and for produce transportation should all be kept clean until used. If any of the containers are reusable, they should be cleaned regularly with more frequent washings if they become overly soiled. Store empty containers away from non-sanitary conditions (near waste receptacles, animal-infested areas, etc.).
● If practical, harvest containers should not be allowed to touch the ground in the field (or in storage), as this may transfer pathogens from the soil to the produce.
● Any commodity that grows on or in proximity to the ground should have extra care taken to control soil contaminants, particularly at harvest time.
● Practice animal and insect control in and around packing facilities. Cleaning and sanitation of packingline equipment is critical. Clean with detergent and physical labor (such as scrubbing or pressure washing, etc.). Use sanitizers of various types to kill microbes on clean surfaces: walls, cooler coils, ceilings, etc., as appropriate.
● If using a dump tank or hydrocooling system, sanitizers (e.g., chlorine) used to reduce vegetable pathogens may help control human pathogens as well (must be labeled for this use). Wherever possible, drain and clean tanks daily. Be sure to rinse out any cleaning solutions before re-filling the tank. Vegetables should not be allowed to sit in water for extended periods of time. Monitor water temperatures. Water that is too cold can cause infiltration into vegetables.
● Keep employees who are ill away from produce. Employees who handle produce should not have open wounds or sores. Workers who handle fresh produce should wash hands frequently and hand washing should be emphasized when using toilet facilities.
● Keep produce cool to reduce pathogen multiplication.
● Keep store rooms and vehicles clean.
Information was taken from the Southern Regional Fresh Produce Food Safety Training Program.
A great source with links to publications on the topic of produce safety for growers can be found at this web site at North Carolina State University: http://henderson.ces.ncsu.edu/content/foodsafety.