Where's the Meat?
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 meathighly
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
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
Agricultural Research Service Information Staff.
"Where's the Meat?" was published in the January 2004 issue of Agricultural Research magazine.