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Keeping your carcass clean.

Keeping Your Carcass Clean

James S. Dickson, a microbiologist at the Roman L. Hruska Meat Animal Research Center (MARC), and Maynard E. Anderson, an agricultural engineer at Columbia, Missouri, have teamed up to help ensure that the public is getting the cleanest meat possible.

The external carcass surface can become contaminated during slaughter by dirt and mud. Removing hide and hooves and immediately washing and sanitizing the carcass will stop the bacterial threat, the researchers say.

Anderson and several colleagues have invented and patented an automatic high-pressure carcass washer that removes most of the foodborne pathogens found on the carcass surface. "A good washing will remove about 90 percent of the bacteria on a carcass," says Anderson.

In the past, the packing industry has used a weak chlorine solution to kill harmful organisms. Currently, natural organic acids are used for sanitation.

ARS researchers have studied the effectiveness of the organic acids on carcasses contaminated with bacteria including Enterobacteriacea, Escherichia coli, and Salmonella typhimurium.

Lactic and acetic acids were tested, as were combinations of lactic, acetic, ascorbic, and citric acids. The scientists changed the temperatures and combinations of acid in search of the most effective treatments.

They found that, in general, increasing either the concentration or temperature of the acids resulted in a greater reduction of bacterial contamination.

At all temperatures, lactic acid was most effective against Salmonella bacteria. Acetic and lactic acids, as well as one of the acid combinations, were equally effective at 160 [degrees] F against Enterobacteriacea and E. coli. The acid mixture worked best at 114 [degrees] F and 160 [degrees] F; the mixture and lactic acid alone performed equally well at 68 [degrees] F.

"There was no magic acid that was effective on all types of bacteria," Anderson says.

Results also indicate that repeated applications of the organic acids, applied with the carcass washer, are more effective than a single application at reducing numbers of pathogens. Much of Dickson's work with sanitation has concentrated on reducing Salmonella contamination in beef.

So far, Dickson has succeeded in cutting Salmonella contamination in beef by 99.9 percent in laboratory tests. Now he faces the challenge of achieving those same results on the slaughterhouse floor.

Consumers can help minimize risk of ingesting Salmonella bacteria by ensuring that beef is cooked properly.

"Heat kills Salmonella, so well-cooked meat isn't contaminated," says Jane F. Robens, ARS National Program Leader for food safety. "However, beef is not always well-cooked. That's why the sanitation work is so vital."

While washing and sanitizing are effective in cleaning the beef carcass, scientists at MARC are also trying to eliminate Salmonella before slaughter.

Ed K. Daniels, a microbiologist, and Neal E. Woollen, a veterinary medical officer, are searching for a quick, accurate way to detect Salmonella bacteria in live cattle.

Currently, the animal's feces is checked for the bacteria. "But we've found through testing that this method really isn't very reliable," Daniels says.

Salmonellosis can be in the tissues but may not appear in the feces. "Hopefully we can use this knowledge to develop a test for identifying salmonellosis in a herd that's a better indicator of the infection than fecal sampling," says Daniels.

He is working on a rapid diagnostic test to detect multiple strains of Salmonella bacteria in tissues, feces, and blood. Once scientists are able to evaluate the presence of the bacterium, they will turn to developing methods to prevent initial infection and possibly rid infected animals of the disease.

"There are several researchers who are developing faster, less expensive, more accurate methods to ensure a safe food supply," notes Robens.

William A. Moats, a chemist at the Beltsville Agricultural Research Center at Beltsville, Maryland, is one of those researchers.

Moats has found a better way to detect penicillin residues in beef. Just as a human may take antibiotics or other medications, cattle are also given drugs to rid them of disease. Some of these drugs may stay in an animal's system and be present in the meat.

"What we have developed is a procedure to detect residues of several types of penicillin in beef tissues," says Moats. However, the test must be reviewed by the U.S. Food and Drug Administration and USDA's Food Safety and Inspection Service before it is used in the regulatory arena.

"It's very difficult to separate penicillin from the enormous number of natural compounds, such as vitamins and amino acids, that interfere in the test," Moats says.

Microbiological tests have been used in the past to detect the drug, but the accuracy of the test was uncertain.

"But we've developed a method using high-performance liquid chromatography (HPLC) that enables us to find minute traces of penicillin in beef," he adds.

In Moat's test, extractions from beef tissue are analyzed using HPLC. A graphic readout from the HPLC equipment indicates that a drug is present.

A duplicate extraction sample is treated with a specific enzyme that destroys penicillin, and the second sample undergoes HPLC analysis. If the subsequent readout does not indicate the presence of a drug, this confirms that the drug pinpointed in the first sample was penicillin.

"This method is very sensitive," says Moats. "We can detect levels of residue much smaller than the Food Safety and Inspection Service's tolerance level of 50 parts per billion."

This HPLC procedure detects penicillin V, cloxacillin, and penicillin G, the most common form of the drug. A negative HPLC result provides unequivocal proof that residues of the drugs are not present at or above the sensitivity limits of the method. A positive HPLC result may require further verification.

Moats has also developed HPLC procedures to detect several other animal drugs. However, enzyme systems that will neutralize those drugs are not yet known, so other confirmatory tests must be used.

PHOTO : Microbiologist Gregory Siragusa obtains samples for microbial analysis from a washed carcass while food technologist James Dickson records information about the sample. (K-4284-12)
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Author:Gerrietts, Marcie
Publication:Agricultural Research
Date:Jan 1, 1992
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