“When I started 10 years ago, I went out into the community and asked what was needed,” said University of Vermont agriculture engineer Chris Callahan. “I got the sense that an area that was needing attention for diversified farms … was post-harvest work: pack sheds, coolers, bagging tables things like that.”

Callahan also serves as the director of the Northeast Center to Advance Food Safety, one of four USDA-funded regional centers tasked with coordinating training, education and outreach related to the FSMA Produce Safety Rule and the FSMA Preventive Controls for Human Foods Rule.

Specifically, Callahan saw the need to establish common sense practices and protocols for cleaning food contact surfaces used by growers. One practice Callahan advocates for is what he somewhat reluctantly refers to as “dry cleaning.” He’s reluctant because he doesn’t want growers to toss aside this important strategy thinking it has to do with keeping their delicates clean.

Dry cleaning, according to Callahan, means cleaning food contact surfaces with brushes, brooms and/or vacuums. “Dry cleaning is one of the most underutilized practices on a produce farm. If there are things that normally don’t get wet, let’s clean them without adding water. Adding water can be a problem,” Callahan said.

Adding water creates moist conditions, and moisture is one of the six factors of the acronym “FAT TOM” – food, acidity, time, temperature, oxygen and moisture. Each of these factors can contribute to foodborne illnesses.

According to Callahan, most produce safety training does not emphasize the drying part of cleaning. Even if water and liquid detergents and sanitizers are used, most food contact surfaces are supposed to be allowed to dry thoroughly afterward. “It can be really difficult if equipment has sandwich seams or little niches that are hard to clean, let alone dry. That’s been some of the motivation landing on this dry cleaning strategy,” he said.

The idea is to be intentional with cleaning procedures to avoid introducing a new risk, which is what can happen when food contact surfaces are not allowed to dry. Dry cleaning tools (brushes, brooms and vacuums) allow the bulk of debris to be removed without adding moisture.

Chris Callahan

Callahan cited the process of cleaning cured onions as an example. Regardless of whether a grower is using specialty equipment or a simple slatted table set-up, at the end of the day the food surface is covered with soil and onion peel fragments. He said one approach is to douse the area with a hose and add some detergent. A better option is to simply brush it with a hand broom or use a vacuum.

If the wet option is taken, Callahan pointed out that not only do the onion surfaces get wet but potentially the legs of the table, the floors and the walls. Soil and onion peels may end up sticking to these wet surfaces. “Now you have introduced moisture and food – remember ‘FAT TOM’ – into a space that isn’t going to dry out,” he said. “Even if you are not motivated by produce safety, I like to make the point that you are now harboring plant pathogens in that space, which can impact produce quality or storage quality.”

Other food contact surfaces that make sense to keep dry are storage containers used for dry crops such as apples or potatoes. According to Callahan, there is likely no reason why these types of containers need to go through a water-based sanitation process regularly. They can be brushed or vacuumed clean.

If, however, the containers need a more thorough cleaning, Callahan suggested alcohol-based wipes and air-dry sanitizers, which can provide cleaning without introducing water. These products are made to dry quickly and completely. To see a list of recommended waterless cleaning products, check out Callahan’s UVM extension blog post “‘Dry Cleaning’ on Produce Farms: Alternatives to Using Water & Detergents” at tinyurl.com/yeupes8k.

“I am not anti-water. Don’t get me wrong. I just want to encourage farmers to think about what is being cleaned and whether a dry approach could be appropriate for the daily tasks,” he said.

Compressed air is another waterless cleaning tool that growers may opt for, but Callahan prefers being able to capture the debris being cleaned off. If growers do opt for compressed air, he advocated for food-grade lubricants and a better-than-average filter.

He also avoids pressure washing for cleaning produce equipment. In his opinion, pressure washing can just spread a problem instead of containing and getting rid of it. For example, using a pressure washer to clean out a narrow gap on a piece of equipment can take what is in that narrow gap and spread it all over nearby walls and other equipment.

Air compressors and pressure washers, however, can come in handy for deep cleaning at the end of the season. He encouraged growers to think of their frequent cleanings as dry cleanings. Then, at the end of the season, growers can do a deep clean with water and detergent, taking care to make sure that the equipment dries completely. Deep cleans usually involve some disassembly to ensure that hard to reach locations get cleaned.

Whether it’s a quick dry clean or an end-of-the-season cleaning marathon, cleaning can be a daunting and overwhelming process. Callahan said to take a deep breath and feel free to reach out to Extension or one of the USDA food safety centers.

“Have confidence that you know what clean looks like. It’s easy to get wrapped up in the lingo and jargon and the rules and expectations of others. Just start with understanding what you’re trying to do,” Callahan said. “Let your guiding principle be to ask yourself if you would eat food from that surface because that is what you’re asking customers to do.”

by Sonja Heyck-Merlin