Near infrared spectroscopy

Near Infrared Spectroscopy – a tool for the development of industry and research

William Herschel, a successful musician and astronomer, wrote in 1800 two articles describing the behavior of the solar radiation spectrum in relation to temperature effects.

Herschel used a glass prism to disperse sunlight and measured the temperature in each color, noting that the temperature increased as he approached red and, taking temperature measurements after red, where there was no visible light, found even higher values, demonstrating the existence of components of light that were not visible to human eyes. This radiation was then called infrared.

Later, around 1905, physicist William Weber Coblentz, observed that two different chemical compounds did not have the same spectra and identified certain patterns in the spectrum, which made it possible to use infrared radiation to obtain structural information on the compounds, thus spectroscopy as a new chemical tool.

Spectroscopy is based on the interaction of electromagnetic waves at a given wavelength with the constituents of the sample, generating a spectrum as a graphic result (equipment response vs. wavelength).

Although its discovery was made more than a century ago, near infrared spectroscopy (Near Infrared Spectroscopy-NIRS) is quite recent, with about 50 articles written on the subject until 1970. This is due to the difficult understanding of the spectra generated in this region (from 700 to 2500 nm), which have many weak and overlapping peaks of overtones and combination bands. In the late 1970s, the emergence of chemometrics, a science that applies statistical methods to chemical data, allowed spectral complexity in the Near Infrared-NIR region to be better understood and used. From then on, the technique started to gain acceptance and became an alternative as a measurement method.

Among the advantages of the method stand out: quickness in the determinations (a sample is analyzed every minute), preservation and minimum sample preparation, dispenses with the use of chemical reagents in the forecasting phase and application in a wide range of materials (can analyze any molecule containing CH, NH, SH or OH bonds). These characteristics make the method an agile, cheap and clean alternative, since it does not generate waste. However, it is emphasized that the quality of the results obtained by this technique is dependent on good and acceptable reference methods, through which the NIR equipment is calibrated.

With so many attractions, the technique started to be applied in several fields of industry and research, for example, in the food, oil and fuel, pharmaceutical, cosmetic and polymer industries, as well as in environmental and clinical analyzes. However, it was in the agricultural area that the technique found greater application, and its intensive use mainly in the area of ​​precision agriculture made it possible to launch the technology on the market and further develop it. The growing demand for high quality products and supplies obtained in the various industrial and productive sectors, highlights the need for quality control in production processes.

Brazil has shown experience in the adequate treatment of data generated by NIRS with many groups in activity across the country, employing or developing chemometric methodologies and calibrations suitable for use in routine research and analysis. An example of this has been observed at the Brazilian Agricultural Research Corporation – Embrapa, which has up to now 26 NIR equipment spread throughout Brazil, in its various Research Centers, which are connected in a network called “Rede NIR”, joining efforts to improve their knowledge in the areas of spectroscopy and chemometry in order to create robust and reliable multivariate calibration models for different chemical parameters and different matrices, such as forages, grains and soils.

Embrapa Gado de Leite (Juiz de Fora, MG) has NIRS equipment, in which around 80 calibration models were developed and are used in the routine of the Unit’s Food Analysis Laboratory. These calibrations allow rapid results to be obtained for moisture, crude protein, ether extract, neutral detergent insoluble fiber, acid detergent insoluble fiber, cellulose, lignin, “in vitro” digestibility of dry matter and mineral matter, in samples forage, silage and corn.

Undoubtedly, with so many applications and several others not yet explored, NIRS technology proves to be a good tool to contribute significantly to the development of industry and research.

he use of this new protocol, which was developed using the Near InfraRed Spectroscopy (NIRS) technique, allows detecting, from the spectral footprint of a sample of coffee, coffees from different regions or species. This technology has been successfully implemented in coffee and other agri-food products.

The use of this new protocol, which was developed using the Near InfraRed Spectroscopy (NIRS) technique, allows detecting, from the spectral footprint of a coffee sample, coffees from different regions or species. This technology has been successfully implemented in coffee and other agri-food products.

In order to use this type of technology, the Federation’s research center -Cenicafé- began to create, since 2004, a database of Colombian coffee spectra from all regions of the country. Since 2006, the collection and analysis of the different origins has been carried out with the financing and cooperation of the Inter-American Development Bank, with resources from the MIF – Multilateral Investment Fund – which supports innovative projects.

The use of these tools will also be a control factor for the Regional Denominations of Origin, since it manages to differentiate coffees from the different regional regions of the country. It is hoped that it can be used to protect the reputation of the different Colombian producing regions, such as the Café de Nariño, the first region that has been declared a regional DO.

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