Fourier transform infrared (FTIR) spectroscopy is considered to be one of the most powerful techniques for chemical analysis in recent years, and is making new inroads into several applications in biological analysis, including food. Fourier transformation (FT) is a mathematical procedure that is applied to the interferograms to obtain the spectrum. Essentially, FT breaks down the interferogram provided by the interferometer into sine waves for each wavelength in the light. These sine waves are arranged over the wavelength to produce the conventional spectrum. Many different types of materials and components are available for FTIR construction. The important components of an FTIR spectrometer are the interferometer, source, beam splitter, detector, and laser. One of the most important components of interferometer is the moving mirror that is required to control its position precisely in order to obtain an accurate measurement of spectra. The function of the detector is to transduce the light intensity received by it to electrical signal. Two most commonly used detectors in both FT-near-infrared (FT-NIR) and FT-mid-infrared (FT-MIR) instruments are the deuterated triglycine sulfate (DTGS), detectors and the mercury cadmium telluride (MCT) detectors. © 2009 Elsevier Inc. All rights reserved.