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Continuous antimicrobial belt treatment reduces and controls microorganisms
by Scott L. Burnett, PhD
Application of a sanitizing solution registered with the Environmental Protection Agency (EPA) to conveying equipment during production can help reduce the incidence of undesirable microorganism contamination on critical meat, poultry, fruit, and vegetable conveyor surfaces. Such sanitizers, approved for incidental food contact, can provide critical intervention. Benefits of a continuous antimicrobial belt treatment include protecting your brand and investment in product, reducing and controlling microorganisms on conveyor belts, and possibly enhancing product shelf life.
A successful continuous or intermittent belt treatment program requires the use of an EPA-registered sanitizer. The product use directions will indicate organism efficacy, sanitizer concentration, and sanitizer exposure time. In addition, the product injection system, spray bars, and valves must be compatible with sanitizer chemistry.
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In any meat processing plant, fat and meat residue accumulate in conveyor transfer belts throughout the production day. This creates an environment in which microorganisms can increase as a direct result of cross-contamination between products and belt, resulting in as much as a six-log increase from the beginning to the end of the production day.
Continuous treatment of the belt with an EPA-registered antimicrobial product helps reduce and control those microorganisms. The level of success achieved depends on the choice of sanitizer, adequate feed and control equipment, and proper application. The product conveying system must be cleaned and sanitized prior to start-up. An EPA-registered sanitizer approved for incidental food contact, with label directions for use as a continuous belt treatment, must be used for this application. Additional consideration should be given to the desired outcome in terms of sanitizer formulation and efficacy.
A recent study conducted by Zhinong Yan et al at Michigan State University and presented at the 2008 meeting of the International Association for Food Protection assessed the efficacy of two liquid sanitizer products at label-use concentration in killing Listeria monocytogenes inoculated onto interlocking and continuous conveyor belts. A peroxyacid-based product and a sodium hypochlorite-based product were evaluated; water was the control.
A short-track conveyor was equipped with both interlocking and continuous belts that looped through a vessel of 10% turkey slurry contaminated with L. monocytogenes. The belts were conducted through the meat slurry five times and allowed to dry for 15 minutes and were then sprayed with sanitizers for up to 60 minutes. Microbial analysis of belt surfaces was conducted at frequent intervals for the duration of the treatment. The study was repeated three times.
The peroxyacid-based sanitizer resulted in significantly (P�0.05) greater microbial reductions on interlocking belts than the sodium hypochlorite-based sanitizer and the water control. After 20 minutes of treatment with the peroxyacid-based sanitizer, populations of the pathogen were reduced by almost five logs; the sodium hypochlorite-based sanitizer reduced L. monocytogenes by less than four logs after 60 minutes.
On the continuous belt, the peroxyacid-based sanitizer was again significantly more effective (P�0.05) than a sodium hypochlorite-based product. A five-log reduction was achieved after a five-minute application of the peroxyacid-based sanitizer, whereas 20 minutes was required to achieve the same level of efficacy with the sodium hypochlorite-based product.
Under the conditions of the study, the peroxyacid-based sanitizer was more effective than sodium hypochlorite in killing L. monocytogenes on contaminated conveyor belts.
There are several things to consider when installing and using chemical injection systems. First, consider the location of personnel and equipment. The use of spray bars will always involve over spray, misting, dripping, or chemical odors. Avoid locating the spray bars on overhead conveyors when there are personnel working underneath or near equipment that will be adversely affected by water or chemical exposure. If the location demands it, install drip pans to protect personnel or equipment.
Another important thing to note is that spray bars are designed to operate using a specific distance from the nozzle to the belt surface; prior to installing one, be sure you know what distance the spray bar is designed for. Placement of the spray bars is critical for the successful operation of the belt sanitizing system. Spray bars are an active part of this system.
Even though spray bars have no moving parts, they do require maintenance. Remember, nozzle performance will deteriorate from normal use. In order for the system to operate properly, the chemical injection system must be in good working order. A malfunctioning chemical injection system could contribute to contamination.
There are several things that should be kept in mind when using these systems. Spray bars are designed for a specific width, for example, and each spray bar has a width range; you must be sure to install the correct spray bar. It is normal for the bar to be about six inches longer than the belt is wide, both to help ensure coverage and to provide an area for attaching the spray bar.
Another thing to remember is to angle the spray bar. It is possible to angle it to accomplish the desired distance from the nozzle tip to the belt surface. Make sure to angle the spray in the same direction as the belt is moving. Having the spray and the belt moving in the same direction will reduce misting, over spray, and odor. Remember, the purpose is to achieve complete belt coverage.
Spray nozzles can become covered with product. Be sure that the location of the spray bar does not allow it to come into direct contact with product or to be splattered. Also, be sure to locate the spray bars to allow ease of maintenance. Automatic and manual valves must be accessible. Place the spray bars and valves in the same area to allow for easy manual shutdown and valve maintenance.
Sanitizer Solution Header
The sanitizer solution header is the supply line to the spray bars and should not be overlooked. The following are suggestions and guidelines:
- Install a new header if possible. A header system that has been used for another purpose may contain sediment, soil, or chemical residue. Residue from previous use may inactivate the antimicrobial or adulterate the food.
- Flush all lines thoroughly. Even a new header system will contain debris that could contaminate the product or clog nozzles. Do not connect the spray bars to the header until the system is flushed. Only when flushing is complete is it safe to connect the spray bars.
- Compensate for expansion. When using PVC pipe, be sure to allow for expansion and contraction due to temperature changes. Failure to do so can result in premature failure of the header system.
- When running the sanitizing header overhead, some applications require a secondary containment to prevent contact with personnel in the event of a leak.
- It is impossible to give a standard sizing recommendation for all applications. Total flow needs to be calculated for the entire system and for each leg of the header. The size of the nozzles and the pressure required also play a part in the selection process.
- In addition to locating the valves for easy access, it is important to install them in the correct sequence. The manual valve needs to be installed ahead of the automatic valve to allow for servicing of the automatic valve.
- There are two places to consider the air lines that the system requires. The first is the air supplied to the control panel. The second is the lines from the control panel to the automatic valves. The most important things to consider are the materials to use and the pressure required. Because of the low volume of air needed, the length of the air lines is of little concern in normal applications up to 200 feet.
- Follow all local and national codes for control panel installation. Ideally, the control panel should be located out of high-traffic areas and away from any area where it may be exposed to excessive amounts of water.
- Filters and strainers should be installed prior to any use of the system.
Continuous antimicrobial belt treatment helps reduce and control microorganisms throughout the production day. Using an EPA-registered sanitizer with label directions for continuous or intermittent belt treatment, adequate feed and control equipment, and proper application, combined with the expertise and support of your sanitation supplier, will help protect your product and your brand.
Dr. Burnett is a senior program leader for Ecolab Inc., Food & Beverage Division. Reach him at firstname.lastname@example.org or (651) 795-5859.