Composition analysis of beef rib sections by dual-energy X-ray absorptiometry

Dual-energy X-ray absorptiometry (DXA) was used as a non-invasive method to measure composition of 9, 10,11 - rib sections obtained from 80 beef carcasses. The weights of the rib sections ranged from 2986 g to 6394 g. Each rib section was scanned twice by DXA, once in a horizontal or standing rib position (DXA-1) and once in a vertical position (DXA-2). After scanning, each rib section was dissected into fat, muscle and bone. The intramuscular fat content of the longissimus muscle was measured chemically. Dissected lean and fat values were adjusted for the amount of intramuscular fat. DXA lean values were adjusted for amount of bone (less bone mineral content). Both DXA measurements consistently overestimated the amount of fat relative to dissection. The DXA-1 scan position measured more lean and less fat than did DXA-2. The correlation (r) between the amount of dissected lean and DXA-1 and DXA-2 lean was 0.91 and 0.85, respectively and between the amount of dissected fat and DXA-1 and DXA-2 fat was 0.94 and 0.92, respectively. The high correlations between DXA and dissection results indicate that DXA could be used as a non-destructive method for evaluating composition of cuts of beef; however, attention must be given to orientation of the cut during the DXA scan.