Keeping produce clean from the time it’s harvested to the time a consumer purchases it is a challenge for every grower.
Lindsay Gilmour, Organic Planet LLC, has been a food safety educator since 2013, and said most food safety issues in the news are caused by biological pathogens, primarily bacteria and sometimes parasites or viruses. “We don’t hear as much about physical and chemical contamination, particularly physical,” she said. “There are a lot of food safety recalls because of bits of plastic or glass or paper in food.”
On the farm and in the packing shed, chemical storage can present problems, so any chemicals should be stored so there is no chance of contamination. Physical considerations include shards from glass, which can be from a number of sources including lightbulbs or glass windows. “If you have any kind of equipment with gauges or lights that have glass or hard plastic covering, if they smash, will it be a problem?” asked Gilmour.
Wood chips can introduce contaminants, so it’s important to monitor the condition of shipping pallets or boxes. Rocks are often brought in from the field in produce boxes, wheeled equipment, on shoes or in harvested produce.
The most common bacteria that reach fresh produce include E. coli 0157:H7, Salmonella, Listeria and Campylobacter. Parasites are most likely to be Cyclospora or Cryptosporidium; viruses are usually hepatitis A or norovirus. Spread of these contaminants is most often due to contaminated water that’s the result of people not following basic hand washing hygiene, wearing dirty shoes, having dirty outer clothing or using dirty equipment.
Gilmour explained the importance of knowing what to do immediately if crops or food contact surfaces which are contaminated. “Stop work, isolate the area that’s affected, isolate the product that’s affected and dispose of affected crops,” she said. “Clean and disinfect the equipment and surfaces that were contaminated.”
It’s important to differentiate cleaning from sanitizing. Cleaning is removing dirt and debris from surfaces; sanitizing is treating the clean surface to reduce or eliminate pathogens. Gilmour outlined four steps for cleaning and sanitizing: remove dirt and debris, scrub with soap and water, rinse the surface with clean water (because any dirt will deactivate the sanitizer), then apply a sanitizer that is approved for use on food contact surfaces.
Keep a written list of standard operating procedures to ensure all employees understand the processes they are expected to follow. The list can be simple, with an outline of steps and perhaps illustrated with photographs.
Gilmour said Listeria is one of the biggest risks in the wet zone. Sources include cracks, standing water and drains. “It can grow at refrigeration temperature, so you really have to keep things clean to prevent Listeria,” she said. “Salmonella tends to be more in sinks from handwashing that’s coming from animals and people. For E. coli, the source is water, people and dirty tools.” Ideally, floor drainage grates should be removable for washing. Gilmour suggested cleaning and sanitizing drains and placing a screen over drains to catch anything that falls on the floor.
Product flow helps keep things clean. “Efficiency comes with product flow and also the surfaces,” said Gilmour. “They’re easier to clean and dry. Harvest comes in from the field, into the wet zone (washing) to the dry zone. Wet and dry zones don’t cross over and you can do things in an assembly line.”
Gilmour urged growers to make it easy for everyone involved in washing and packing to do the right thing – it goes a long way in sanitation. “Once you have clean, dry equipment, where are you storing it? Are you keeping where it will stay clean and dry until you need it? Harvesting bins should be stored on shelves or on slats, making sure they’re known to be clean.”
Some growers use frames made of wood and chicken wire for spray washing roots, but wet wood can lead to problems. Gilmour said although a wood frame with wire seems like a good design, wood can become moldy or chipped and it’s difficult to sanitize. She suggested anyone using wooden bins or any other wood should scrub, rinse and air dry them completely.
Penn State Extension Educator Jeff Stolzfus offered tips for clean packing. “During packing season, try to keep wagons and trailers out of the packing area,” he said. “If you want to store equipment in the packing shed in winter, that’s great. But during the season, keep that stuff away from the pack line.”
Packing materials should be kept off the floor and on clean pallets. If the packing area is under cover, be sure to look at the space above and check for evidence of birds. Open beams and trusses provide roosting spots for birds and raceways for rodents, so watch for evidence of those pests.
Many farms work in packing sheds that are not in a closed building with sliding garage doors, stainless steel sinks and tables and floor drains. However, growers can make what they have safe. A portable wash station with a sink, packing table, water and appropriate tools for clean-up can be set up in the field for field packing. Used water should be collected and not dropped in the field. The tank that holds clean water for washing should be cleaned and sanitized periodically to avoid biofilm accumulation.
Stolzfus said proper flow of materials helps prevent cross-contamination. Ideally, product from the field should enter one door and exit through another. With coolers, the potential contamination issue is from condensate. Catch pans for water create a damp area great for growing Listeria, so Stolzfus likes to see water drained outside, not dripping inside onto the floor.
Plastic strips placed over doorways to maintain cool temperatures can gather bacteria and can become an unexpected food contact surface. “If you’re going through those with pallets or carts or even carrying things in, a lot can grow on the plastic,” said Stoltzfus. “Those should be on the list of surfaces to clean periodically.”
Cleaning equipment such as barrel washers for root crops are commonly used, but washers made of wood are almost impossible to sanitize. “Think about the crop,” said Stolzfus. “Is it a crop that’s eaten raw? Brush washers made of stainless steel are easy to clean. There should be no brushes or sponges which can be difficult to clean.” He added that conveyer belts can also present a cleaning challenge because it’s hard to get inside surfaces. Flaps (on any equipment) can harbor bacteria and are easy to ignore.
An important consideration for wash sinks is a valve that allows rapid draining. Be sure wash water is discharged in an appropriate manner according to state and/or local regulations. Discharged wash water should not pool or drain anywhere other than where it’s intended to go.
Sink height is important for worker comfort and can be modified by adjusting the legs. Some growers successfully use stock tanks placed in a frame that can be easily removed for thorough cleaning and disinfection.
Clean water, clean hands and clean surfaces go a long way to ensure harvested produce has the best possible chance of reaching the customer as it’s intended – clean and ready for consumption.
by Sally Colby