Animal scientist Alva Mitchell, of the Growth Biology Laboratory at the ARS Beltsville (Maryland) Agricultural Research Center, used dual x-ray absorptiometry (DXA) to measure pork carcass composition. This method is noninvasive and requires little user input in terms of manipulation and data processing. "The technology is based on using x-rays of differing energy levels to scan for soft tissue of differing densities," says Mitchell.
The technology was used in the lab to measure pork carcass composition by performing a total scan of pork carcass halves. Information from selected cross-sections of the image was highly predictive of the composition of the entire carcass.
Hog production has undergone significant changes over the past hundred years. In the first half of the 20th century, market hogs were bred for lard, which was used as a resource during both World Wars. About midway through the century, consumers began looking for leaner meat—highly nutritious but with less fat and calories. The pork industry responded by breeding for leanness. However, it was hard to know just what the lean-to-fat ratio was throughout the carcass without cutting it into its various parts. "Dual x-ray absorptiometry would allow packers to know just what they are paying for: the true value of the meat and not a large amount of fat that gets cut off before shipping," says Mitchell.
Over the years, instrumentation has allowed the fat-to-lean ratio to be determined with an acceptable degree of accuracy. Now, rapid, accurate methods are needed to provide information regarding the fat and lean content during the on-line processing of pork carcasses.
The DXA instruments Mitchell used scanned cross-sections of the carcass at a speed of 7.68 centimeters per second, using pencil-beam x-ray technology. This speed compares to the processing chain speed of 16.6 centimeters per second. Newer DXA instruments use a wide-angle or fan-beam technology that will scan wider sections, increasing scanning speed and making the technology potentially adaptable to on-line evaluation of pork carcasses. Mitchell's next step is to find a commercial packing plant to test the technology, which would require adapting it to the processing environment.—By Sharon Durham, Agricultural Research Service Information Staff.
"Where's the Meat?" was published in the January 2004 issue of Agricultural Research magazine.