X-ray analysis is well known from medical applications and security scanners at the airport, but perhaps not so well known in food production.
The short wavelength of X-rays allows them to penetrate all sorts of materials. Some of the X-rays get absorbed and the rate of absorption depends on the density of the material encountered. For instance, the femur in your leg shows up because it absorbs more X-rays than the surrounding flesh and, likewise, those nail scissors that you forgot to take out of your hand baggage absorb at lot rays and will show up strongly against other items.
The X-ray advantage
X-ray is just one of three main options for testing fat content in meat.
The classical reference analysis is the Soxhlet method. A sample of meat is weighed, the fat is extracted from the sample and weighed, and the fat is calculated by dividing the weight of the fat by the weight of the sample.
Another option is NIR. As discussed on our NIR technology page, Near Infrared is a much faster and more convenient alternative to the reference method. A sample is simply plucked from a production line and tested in a matter of minutes.
X-ray is even faster, but the big difference compared to NIR is in the way it can measure entire batches of meat as they pass through the instrument on a conveyor belt, just like your bag at the security check.
This gives a complete and continuous measurement of entire batches of meat which is particularly useful given the inhomogeneous nature of meat. For example, a batch of meat trimmings will consist of some cuts that have a lot of fat and others that are leaner. Measuring everything gives an accurate assessment of the total fat content allowing effective sorting and segregation leading to better quality and improved profitability in subsequent processing.