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Basic access in analysis and identification organic bonds in food industry use NIR spectrometry

Spectroscopy is the study of the interaction of electromagnetic radiation with a chemical substance. Each molecule has certain natural vibration frequencies. The nature of the interaction depends upon the properties of the substance. When infrared light is incident on the molecule, the frequency which matches the natural vibration frequency is absorbed by the molecule resulting in molecular vibration. Near infrared Spectroscopy (NIR) is a type of vibration spectroscopy in the wavelength range of 780 to 2500nm. This NIR bands are due overtone and combination bands primarily of OH, CH, NH and CO groups. Applications include water content, measure the percentage of proteins, lipids, carbohydrates in food. The absorption of the radiation at the NIR region is attributed to the low mass of the hydrogen atom. The bonds involving hydrogen vibrate with large amplitude. Therefore, the absorption bands observed at the NIR region arise from overtones of stretching vibrations involving functional groups with hydrogen atom or combination involving stretching and bending mode of vibration of these groups. The overtones (1450nm) and combination (1940nm) water bands in the NIR region, spectral bands related to milk. The lipid CH combination and second overtones related at 2320 and 2350nm. The protein NH absorption band at 2060 and 2170nm can be visualized in the wheat spectrum. This information content has been intensively exploited for qualitative and quantities chemical and physical analytical purposes. Instrument selection must be guided by end application. Modern NIR instruments in terms of the technology employed for wavelengths selection: Filter instruments, Led based instrument, AOTF based instrument, Dispersive optics based instruments and Fourier transform based instruments. Stability, reliability, wavelength accuracy, resistance to vibration and temperature change are all factors that determine the performances of the instruments.

spectroscopy; NIR; molecular; wavelength; absorption; food

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