Researchers Create A Simpler Test To Screen Meat For Nerve Tissue Contamination

University of Arkansas graduate student Rahul Gangidi, professor of food science Andy Proctor and assistant professor of animal science Fred Pohlman used Fourier Transform Infrared Spectroscopy (FTIR) to examine ground beef contaminated with spinal cord tissue. BSE prions reside in cerebral and spinal tissue. They reported their results in the Journal of Food Science.

BSE has been linked to deaths in Europe from variant Creutzfeldt-Jacob disease in humans who ingested tainted meat. It has not yet been detected in the U.S. meat supply, but it remains a concern to consumers and meat producers alike. Spinal cord tissue can accidentally contaminate meat as it is removed from vertebrate bones close to the spine. The current method used to detect this contamination is a biological assay called ELISA, a complex, lengthy and expensive technique that examines only tiny samples of meat at a time.

Using ELISA to detect nerve tissue in ground meat is like searching for a needle in a haystack by examining a small sample of straw, Gangidi said. "But this new method could be used on the whole haystack."

The U of A scientists decided to investigate attenuated total reflectance FTIR (ATR-FTIR), a form of infrared spectroscopy, because it directly examines the meat sample, is non-destructive, and takes only two minutes to perform. They first looked at differences between spectra obtained from meat and spinal cord to observe differences that could be used to quantify the amount of nerve tissue in meat.

They bought some ground beef at the local grocery store and obtained spinal cord tissue from the University of Arkansas abattoir. They examined the unadulterated meat using ATR-FTIR. They then mixed spinal cord with a certain amount of meat, then added more meat to dilute the amount of spinal cord tissue present in the beef to obtain various levels of adulteration. They then measured the spectra of the various adulterated samples using ATR-FTIR and statistical analysis to find which portions of the spectra could be used to measure adulteration. They found a strong correlation between phosphate groups bound to organic molecules and the presence of bovine spinal cord tissue: As the concentration of spinal cord tissue increased, so did the presence of the specific phosphate group response. This could be due to the presence of sphingomyelin, a component of the sheath that surrounds nerves that is rich in phosphate. The method detected spinal cord contamination down to 0.0016 percent, a vast improvement over the ELISA, which is sensitive to 0.1 percent. Some meat processing plants already have FTIR machines, so this method may become useful in the industry. Further, meat processors could use the technique in a production line, with an IR scanner similar to the "bar code" scanners used in stores today.

The technique needs further development before it becomes useful to industry, Gangidi said.

"However, the potential is there," Proctor said.