Food Safety in the Packing House

By Chris Blanchard, Flying Rutabaga Works

Chris's Field Day 044As produce farmers, we can’t eliminate the risk of microbial contamination in our food production. We sell a product that we grow as part of the real world–a world filled with the microbes that can make people sick. We can, however, take steps to reduce food safety risks, work to develop our food production systems in ways that reduce the risk of contamination, and restrict the spread and growth of human pathogens if contamination occurs.

The good news for produce growers is that the steps we take to prevent contamination of our produce with microbial pathogens can also reduce the spread and growth of rot and disease organisms. This will result in higher quality products that last longer on store shelves and in our customer’s refrigerators. There are aesthetic advantages, too: nobody really wants to get a CSA box with mud caked on the bottom, or that was nibbled on by mice.

Exclude the Creatures You Can See
The area where we pack our produce should present an inhospitable front to all creatures great and small (with the exception of ourselves). So should the spaces where we store our packaging materials. Rodents, birds, and insects all have the potential to carry pathogenic microbes, as do domestic animals–I’ve seen what my dog rolls in, and I don’t really want that anywhere near my food.

Ideally, animals should be excluded altogether. Packing houses with four walls and a roof should include screens on windows and doors. Large openings should be covered with strip doors or screening to further discourage animals from coming in. In lieu of a fully enclosed packing house, some farmers use heavy duty fabric screening with heavy chains sewn into the bottom to enclose a three-season lean-to. This set-up provides easy access and plenty of airflow. I’ve also seen a small pole barn sheathed in plastic as a place to store harvest tools and containers and do packing in the winter.

If you can’t enclose a packing area, or if you choose to do some of your packing outdoors, secure as much of your harvest equipment as possible in closed containers. Harvest containers that can’t be stored under cover should be stored upside down and elevated off the ground at a minimum.

Even with an enclosed packing area, you might have critters that feel tempted to invite themselves in, or maybe just pass through. Rodents like small spaces and corners, so make them feel unwelcome by eliminating or illuminating these spaces. A significant gap between the wall and anything stored near it will leave mice and rats feeling exposed, and make it easy for you to monitor for the presence of feces with just a glance.

Birds can be discouraged with predator decoys and “scare eye” balloons–large balloons with a bulls-eye pattern that resembles a raptor’s eyes. Place these around the packing area to discourage birds from coming near, then staple bird netting against open rafters to deny the brave ones the opportunity to roost above the areas where you handle food and store equipment and supplies.

Limiting food and water sources also can discourage rodents, birds, and other undesirable additions to your packing area. Produce trimmings should be removed from the packing area at the end of every day, hopefully to a compost pile located at a distance from the packing house. Concrete floors make it easy to sweep and wash away even small scraps, and facilitate good draining. Packing on gravel or grass makes in almost impossible to remove all of the food waste from the packing area, and surface puddles can attract and sustain rodent populations.

Constant moisture also provides a fertile breeding ground for organisms like Listeria monocytogenes. Porous ground coverings such as dairy brick or gravel can allow moisture to build up below, and pathogens have the potential to move across the porous layer. A cantaloupe-sourced outbreak of Listeria monocytogenes at Colorado’s Jensen Farms, which killed 33 people in 2011, was caused by bacteria harbored in puddles on uneven concrete floors and floors with an inadequate slope. If your concrete floor doesn’t drain well, use a large squeegee to move water towards a floor drain or out the door after a day’s work, so that the floor can dry out.

Pests that do get into the packing area should be killed or captured and removed. For insects, I’ve had good luck using the Mr. Sticky Fly Tape System to significantly reduce fly populations in the packing area. This skinny sticky tape runs from one reel to another above the packing area, and can be wound onto a spool when it’s full, exposing fresh sticky tape to more flies.

Poisons–even OMRI-approved poisons–should not be used to control rodents in the packing house. Most rodenticides need time to work, and poisoned mice and rats may crawl off to die in a place you don’t want them–like a bin of carrots, or in the middle of your box storage. At Rock Spring Farm, we use “tin cat” repeating mouse traps to monitor and control rodent activity; the kind with a window in the lid make it easy to check traps weekly. If we find any evidence of rodent activity, such as a trapped mouse or feces, we label the area a “hot spot” and upgrade our monitoring and control efforts until the area is rodent free for 10 days. Shortly after we instituted our monitoring program, we expanded it to include our cover crop seed storage and our greenhouses, and dramatically cut down on rodent damage in those areas.

Manage to Control Bacteria
In the same way that we want to make packing areas inhospitable to the critters we can see, we want to make them inhospitable to the critters we can’t see, too.

The equipment you use for harvesting and packing produce, from knives and totes to tables and wash lines, should be easy to inspect, maintain, clean, and sanitize. Small cracks and rough surfaces can hold small amounts of water, which allow bacteria to survive by shielding them from full contact with sanitizers. Cracks and rough areas allow pathogens such as E. coli 0157:H7 and Salmonella to persist and reproduce.

Even smooth surfaces such as stainless steel can be contaminated with microbes. Cleaning and sanitizing surfaces–especially food contact surfaces like tables, tanks, and wash lines–keeps microbes from multiplying on small particles of nutrient-rich soil and drops of plant sap. It is best to clean and sanitize all of your harvest and packing equipment at the end of every day, and to sanitize again before you use them in the morning.

Most sanitizers don’t work in the presence of soil or detergents, so it’s important to remove these before you apply a sanitizer. Sanitizing is usually a four-step process: rinse, clean, rinse, and sanitize. Rinse to loosen the initial soil and remove some of it. Use plain old elbow grease or a detergent like Simple Green to loosen any soil that remains on the surface. Rinse away the detergent and remaining soil with more water, then apply the sanitizer.

In the packing house, sanitizers are used both to sanitize hard surfaces and to sanitize wash water. Like any pesticide, the sanitizer you use must be labeled for its intended purpose, and you need to use it at the correct concentration. Weak solutions aren’t effective, and solutions that are too strong can damage the surface you’re sanitizing.

For a hard-surface sanitizer–for killing microbes on work surfaces and containers–I prefer a hydrogen peroxide-acetic acid blend such as BioSafe’s SaniDate 5.0 or Ecolab’s Oxonia Active. The combination provides effective control over a wide range of water pH, and breaks down into water, oxygen, and acetic acid. Both products are OMRI-approved for organic production.

If you submerge produce in water, you should use a wash-water sanitizer. Wash-water sanitizers won’t eliminate pathogens on contaminated produce, because plant surfaces are full of crevices and cracks where bacteria can avoid contact with the sanitizer–but they do keep bacteria from spreading from one piece of produce to another. Many growers use Ecolab’s Tsunami 100; BioSafe’s SaniDate 5.0 also is labeled for use as a wash-water sanitizer. Both are hydrogen peroxide-acetic acid blends, and approved by OMRI for use in organic production.

Because they are so often moist and dirty, floors always should be considered contaminated. In the ideal food-safety world, produce containers would never touch the floor. Small and large pallets can elevate produce off the floor so that draining water and soil don’t contaminate the container or its contents. This also keeps your boxes clean and presentable for customers, and eliminates dirty crates at farmers market.

Chris Blanchard provides consulting and education for farming, food, and business through Flying Rutabaga Works. He has worked in farming for the past 24 years, managing farms and operations around the country. As the owner and operator of Rock Spring Farm since 1999, Chris raised 20 acres of vegetables, herbs, and greenhouse crops, marketed through a 200-member year-round CSA, food stores, and farmers markets. 

November/December 2013

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