Beyond Soap and Water
By Tom Wray, associate editor

It seems a simple-enough process, but carcass washing remains vital to maintaining food safety.
Washing can seem like a simple and given step in the meat-preparation process. However, it can also be more complex and vital, especially when the action is carcass washing.
“Some consider the entire process of cleaning and decontaminating a carcass to be the collective ‘carcass wash,’ ” says Gary Acuff, the head of the Animal Science department at Texas A&M University. “For others, the carcass wash is only the water rinse used to remove dust, blood, etc., from the carcass surface. I consider it to be the entire process, including the water washes to clean the carcass surface and any antimicrobial compounds sprayed on the surface for decontamination.”
The washing does begin in a simple way, with the rinsing of carcasses as they start the process. The first wash is done right after slaughter to remove contaminants, blood and fecal matter, says Craig Wyvill, chief of the Food Processing Technology Division (FPTD) at Georgia Tech Research Institute. The carcasses are washed again at the eviscerating line, both inside and out. Wyvill says chillers that use water can also be part of the washing.
The use of water, obviously, is basic. The complexity comes in guaranteeing the elimination of contaminants.
“The processor must assure that antimicrobial applications are of a consistent concentration, and that they are applied with a consistent volume, pressure and temperature,” Acuff explains. “The process must be validated to provide a measurable reduction of bacterial hazards, and then the decontamination process must be thereafter applied following the same application parameters that were validated earlier in order to have confidence in a consistent bacterial reduction during the normal processing day.”
According to John Pierson, principal research engineer at FPTD, the issue to be aware of with any method is cross-contamination. If there is fecal material present, it can be embedded into the bird. And it can happen because of the process itself with the carcasses touching each other or from the people who are working on the line. Wyvill adds that chemicals used can be a hazard themselves. Many plants use chlorine as a disinfectant.
“Use too much, and you can create gassing [of chloramines] as a safety issue that you have to protect against,” he says. “You can’t focus on the process without focusing on the implications.”
The right equipment
The tools needed for effective carcass washing depends on the method and plant. As Wyvill said, the first rinse and the water chiller can be used for some of the washing. But tools are limited to that.
“Equipment can range from very simple and inexpensive to quite costly and complicated,” says Wyvill. “Effectiveness can be just as good with either system, but the more expensive systems will provide more rapid and consistent application with less labor investment.”
With the use of antimicrobials, it depends on the needs of the individual plant. Dr. Margaret Hardin, an associate professor of microbiology at Texas A&M, says that high-volume plants will use automated cabinet systems along with or near the final water wash cabinet. The systems available range from a hot water deluge to a hot water and organic acid spray system or a steam tunnel.
“In the case of smaller facilities with lower volumes, systems range from smaller, single-carcass cabinet systems to portable sprayers or handheld garden sprayers for the very small plants,” she continues. “These systems are designed to be both practical and cost-effective to the smaller processor.”
Witchita-based Cargill Meat Solutions uses more than method. “During the last 10 years, we invested more than $1 billion in our meat science research, technology and infrastructure, which has helped implement many of these interventions for food safety,” says Angie Siemens, Ph. D., vice president of technical services at Cargill.
Old style
Older methods used only water, usually heated. Acuff says that the first widely accepted method was the use of a chlorine spray mist during cooling.
“The spray was intended to assist in rapidly lowering carcass temperature, but the addition of chlorine helped reduce bacterial contamination,” he explains. Eventually the process became used mostly to control the temperature of the carcasses. At the same time, Acuff says, researchers investigated the use of dilute organic acids for decontaminating.
Unlike the chlorine spray, the acid spray was done hot and while the carcasses were still on the slaughtering floor. This time, explains Acuff, the intent was not to wash the carcass, but to remove bacteria. At the time, most people working on it just wanted to remove bacteria that could cause spoilage, but after an E. coli outbreak in 1992, the emphasis moved to reducing all pathogens and improving food safety.
“Carcass water washing has been pretty much the same for decades,” says Hardin. “As technology has developed over time, carcass washing has become more automated moving from hands-on washing with hoses to automated washing in a cabinet system. Much of the development in automated technology to what we see in plants today has evolved since the early 1980s.”
There has been a lot of research involving use of the air chiller, Wyvill adds. New methods would use tongs to keep the carcasses together and use air agitation to do some of the cleaning.
Acuff goes on to say that new antimicrobial compounds have been developed along with new ways to increase the carcasses’ surface temperature to kill bacteria.
“The new methods are all based on the same original themes — kill the surface bacteria by raising the temperature (hot water or steam) and/or utilize an antimicrobial spray (organic acid or other antimicrobial),” he says.
The use of antimicrobials is where there has been the biggest push in research, according to Wyvill.
Yet, Pierson says, “there are people going back to see the use of hot water alone.” Interest in organic acids also has grown, including some proprietary mixes. Furthermore, attention is being paid to understanding the sourcing of the livestock before it even gets to processing, with the idea being, it is better to control pathogens before livestock reaches the process.
Hardin explains that the use of antimicrobials have increased as research has increased, government approvals have been received and the necessity of food safety has risen. Along with chlorine and organic acids, materials used include trisodium phosphate, cetylpyridinium chloride and their combinations.
“I believe it is safe to say that most red meat plants today use an organic acid (generally lactic or acetic acid) rinse either alone or in combination with hot water or steam,” Hardin says.
Work is being done in alternatives to wash. Wyvill says that researchers are looking into the use of ultraviolet light and ozonation (use of ozone to kill pathogens), though neither are being used commercially. Pierson is looking into disinfecting the liquid streams of the process. The issue with each of these is muscle penetration.
Pierson explains that researchers are always trying to cut back on the use of resources such as water while still balancing food safety, a major issue as many poultry producing areas see increasing droughts.
“We’re trying to see if there’s a way to reuse water and other resources,” he explains. “To do that, you need to clean the water up in terms of solids and bacteria. We’re looking at different technologies that are water-based but also keep cross-contamination down. It’s going to change how we look at food safety.”
Hardin says that a “seemingly endless” variety of antimicrobial methods have been tested and published. As more methods are tested and approved, they will enter the list of options for reducing the pathogens on the carcasses. Irradiation is also gaining attention, she says, but the cost and practicality of it remains under investigation.
Acuff says that washing is just one step in reducing the pathogen load on meat. “Notice, I said, ‘reduce,’” he explains. “None of these methods will eliminate the presence of pathogens, and it should be expected that raw meat will contain pathogenic bacteria at low levels.”
Effective control would include the use of several methods, starting with the live animal and going all the way through the process to the end consumer product.
Water conservation
Wyvill says most older methods relied on the volume of water used. He explains that washing can get very water intensive, up to 250,000 gallons a day. More research today has gone into ways to remain effective, yet be less reliant on large amounts of water.
Georgia Tech’s Pierson says the average poultry carcass wash uses six gallons of water per bird, depending on the strategies of the individual plants. That adds up to millions of gallons of water per year.Wyvill says that the use of water at plants doubled in the 1990s, when droughts started to affect major chicken-producing areas, with more emphasis on recycling.
“We continue to see how much of a valuable resource water is,” says Acuff. “While we may have only worried about cost of water in the past, now we are also focused on conservation. We have to be careful not to conserve to the point where treatments are ineffective, and we must watch to be sure our attempts to produce an affordable product don’t compromise our ability to produce a safe product.”
Siemens says her company has taken steps to control the amount of water plantes use.
“We had an internal goal of reducing water usage by 10 percent,” she says. “We did this by empowering employees to identify where improvements could be made. We had over 280 ideas submitted. Of those ideas, we are in the process of implementing 30 during the next few months.”
All of this comes on the heels of an increased attention to food safety. The USDA’s Food Safety Inspection Service is starting a new standard on pre-placement, using a risk-based assessment, according to Wyvill. That will add more pressure to water and chemical usage, he says.
Ensuring food safety is still the ultimate goal. Acuff says that carcass washing can only do so much. How the carcass is prepared also matters. A small knife cut can create a harborage to protect bacteria such as E. coli O157:H7 that would be killed by hot water or acid spray. Therefore, the more smooth the carcass surface, the better job the washing can do.
“Food safety is everyone’s responsibility,” says Hardin. “Whatever system a processor chooses, they must insure that it is science-based and validated, either through in-plant testing, through an outside third-party or through the published literature.”