Differentiation of meat and bone meal from fishmeal by near-infrared spectroscopy: Extension of scope to defatted samples

Current and future legislation regarding the use of processed animal proteins in animal nutrition requires the availability of robust analytical methods that allow for proper implementation of corresponding legal restrictions. Near-infrared microscopy (NIRM) is a spectroscopic method that allows for the differentiation between meat and bone meal and fishmeal and it is assumed that the different content and composition of the fat is one of the factors responsible for the observed differences. Here a study of the NIRM method has been conducted in order to check for the influence of intentionally introduced reduction of the fat content on the capability of the NIRM method to correctly classify defatted samples. This has practical implications, since processed animal proteins may be defatted by solvents under real world conditions. The results confirmed that the scope of the NIRM method could be successfully extended to samples that have been previously extracted with nonpolar solvents. Only after the use of stricter techniques such as extraction with chlorinated solvents or hydrolysis the NIRM method produced a higher portion of wrong classifications. However, since these extraction techniques are not often used under real world conditions, the impact upon the use of the NIRM method in the feed sector for the specific application of the differentiation between meat and bone meal and fishmeal is minor.