Near infrared spectroscopy in animal science production: principles and applications

Near infrared (NIR) is one of the techniques belonging to vibrational spectroscopy. Its radiation (750 to 2500nm) interacts with organic matter, and the absorption spectrum is rich in chemical and physical information of organic molecules. In order to extract valuable information on the chemical properties of samples, it is necessary to mathematically process spectral data by chemometric tools. The most important part in the development of an NIR method is building the predicting model generally called calibration. NIR spectroscopy has several advantages over other analytical techniques: rapidity of analysis, no use of chemicals, minimal or no samples preparation, easily applicable in different work environments (on/in/at line applications). On the other hand, NIR spectroscopy has some disadvantages: low ability to predict compounds at low concentration (<0.1%), necessity of accurate analysis as reference, development of calibration models required high trained personnel, need of a large and up-to-date calibration data set (often difficult to obtain), difficulties to transfer calibration among instruments, initial high financial investments. In the feed industry, NIR spectroscopy is used for: feed composition, digestibility (in vivo, in vitro, in situ), traceability assessment (to avoid possible frauds). As far as animal products are concerned, NIR spectroscopy has been used to determine the main composition of meat, milk, fish, cheese, eggs. Furthermore, it was also used to predict some physical properties (tenderness, WHC (Water Holding Capacity), drip loss, colour and pH in meat; coagulation ability in milk; freshness, flavour and other sensorial parameters in cheese). Interesting applications of NIR spectroscopy regard issues like: determination of animal products' authenticity and the detection of adulteration (in order to prevent frauds), discrimination PDO (Protected Designation of Origin) and PGI (Protected Geographical Indication) from other non traditional products, detect handling aspects (freezing, thawing or fresh). There is a growing interest in the evaluation of animal products' quality directly on-line to have a continuous control of the production process. Furthermore, new portable instruments are becoming now available, which will allow to easily monitor some processes at the factory (i.e. ripening and ageing of sausages and cheeses).