Keeping It Clean: Sanitizing water is a vital part of produce processing

It’s difficult to think of any kind of produce processing that doesn’t involve water, which is why it’s crucial for all processors to ensure that the water is properly sanitized all the way through the plant, including the water used to clean the equipment.

Elis M. Owens, senior chemist/microbiologist for Birko, an Olathe, Kansas-based company that manufactures cleaning, sanitation, antimicrobial interventions and process chemical formulations, said in processing facilities water is typically sanitized by the addition of chemicals.

“The addition of the chemicals is intended to kill any pathogens that may be present in the water and leave a residual level of the sanitizer that prevents the water becoming a vector of cross contamination between items of produce,” he said. “Chemistries used include sodium hypochlorite, acidified or buffered sodium hypochlorite, peracetic acid or buffered peracetic acid, chlorine dioxide and ozone.”

Randy W. Worobo, professor of food microbiology in the Department of Food Science, Cornell University, said because of the organic material, a lot of dirt is associated with produce and a processor needs to be careful that the sanitizer doesn’t get bound up.

“The issue is that produce itself is organic. A lot of the sanitizers are being bound up by produce themselves, so it takes higher levels of sanitizer and you need the correct sanitizer because of the binding process,” he said. “You have to make sure your sanitizers are at your target concentration and that you’re measuring the active sanitizer for the correct species.”

Worobo notes peroxyacetic acid is commonly used to decontaminate produce, with the water used as a vector to sanitize but also to just wash off produce.

“Anytime you are using water to clean, you want to make sure you have good quality water,” he said. “If you start with poor water, you can contaminate. You need to have some sort of disinfection step to make sure the water is potable.”

Equipment Matters

The equipment needed in produce processing plants include chemical dosing and dispensing equipment, including dosing and recirculation pumps together with in-line and off-line test instrumentation.

When dealing with cleaning equipment, clean-in-place (CIP) often comes into play, as it allows for the cleaning of equipment without its disassembly.

“CIP is a method of cleaning tanks or closed plumbing systems by recirculating one or more cleaning solutions through the plumbing or a spray in tanks,” Owens said. “It is commonly used on equipment that is too large or impractical to dismantle such as storage tanks or produce flumes.”

Worobo said pieces of equipment normally utilized in a produce processing plant are a centrifuge, flume, sprayer and roll bars, but that different products sometimes require different equipment solutions. While CIP can help circulate the cleaner and saves on water and chemicals, the majority of produce processing equipment is not compatible with CIP, he said, adding it’s more common in the dairy and juice industries.

Canned and Frozen

Water used for all food processing applications should be of potable quality. When dealing with sanitizing water for frozen and canned produce, Owens notes that water used in a frozen food processing facility should be treated to the same standards as water used in a fresh or ready to eat (RTE) establishment, as frozen food can be consumed without any further cooking and should therefore be considered an RTE item.

“The canning process is a lethality step and as such should render the produce item sterile,” he said. “GMPs (Good Manufacturing Practices) however still require canned produce to be produced in a clean and sanitary fashion.”

Creative Thinking

Beth Rogers, global marketing specialist with Eaton Filtration, Tinton Falls, New Jersey, said packaged salad mixes comprise 15 percent in the $45 billion fresh vegetable category, and as might be expected for a product intended to go directly from the package to the consumer’s table, washing and sanitizing the produce are absolutely critical elements of the process.

A Tennessee produce processor (who prefers to stay anonymous) is utilizing Eaton’s self-cleaning filters to get the job done. In a recent case study by the company, Eaton explains that inside the produce processing plant, the greens are upended onto conveyors, passing a row of inspectors and sweeping down a flume into the world’s largest salad spinners. It’s in the flume water that the produce is both cleaned and sanitized, which makes the supply, filtration and treatment of that water a major concern.

Discouraged by the water becoming discolored and contaminated with chlorine residue and needing to be replaced every few hours, the owner of the Tennessee plant created an ozonated wash system that applied the known benefits of injecting ozone into water as a means of sanitizing the flume water. Flume water in the plant is now cleaned and recycled in a closed loop thanks to Eaton DCF Mechanically-Cleaned filters equipped with 50-micron wedgewire screens.

According to Rogers, the DCFs continuous filtering capability means the chilled, 50 psi (3.4 bar) flume water is cleaned and recycled in a 211 gallon (800 liters) per minute loop without interruption. Their fine filtering improves the dissolution of ozonation in the flume water, resulting in dramatically cleaner flume water, longer runtimes between water changes and reduced water consumption.

DCF filters also provide the additional benefit of improving the performance of a water chiller in the sanitizing system. Immediately after filtering, the flume water is pumped to a chiller where it is cooled to 5˚ C by spraying the water onto heat exchanger plates.

Challenges Abound

When it comes to sanitizing water, time is the biggest concern to produce processors.

“Produce is frequently harvested and processed in a time-limited window, so plant management frequently looks at the time used for sanitation as production time wasted,” Owens said. “If we shorten the time for sanitation then we have more time available for production.”

Other challenges for effective plant sanitation include not having the proper resources, such as appropriate chemicals, equipment and properly trained personnel; and a management commitment.

“Plant management or company executives fail to grasp the importance of sanitation to food safety and brand protection,” Owens said. “Consequently, they fail to allocate the time and resources needed for effective sanitation programs.”

Food safety can be assured by verifying the cleaning process parameters (cleaning solution concentration, temperature and recirculation time), and by post-cleaning testing using ATP and/or microbiological testing. Employee safety can be assured by training, use of appropriate personal protective equipment and engineering controls.

Keith Loria, contributing writer



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