Qualitative Analysis
Spectroscopy techniques can also be used to provide valuable information about the type, structure and environment of molecules present in food materials.
Atomic or Molecular Type. Each type of atom or molecule has a unique set of energy levels and therefore a unique electromagnetic spectrum. By measuring the electromagnetic spectrum of a material and identifying the magnitude and position of the absorption or emission peaks it is often possible to determine the type of atoms or molecules present.
Molecular Structure. Certain kinds of molecular groups have characteristic absorption or emission peaks in specific regions of the electromagnetic spectrum. For example, certain kinds of molecular groups give absorption peaks at specific wavelengths in an infrared spectrum, while the number, type and organization of atoms and bonds within a molecule leads to characteristic absorption peaks in a NMR spectrum. It is therefore possible to obtain important information about the structure of molecules by measuring their electromagnetic spectra.
Molecular Environment. Spectroscopy techniques can also be used to provide information about the molecular environment of atoms and molecules within a sample. The absorption or emission of energy between two energy levels within a specific atom or molecule is influenced by the presence of other atoms and molecules in their immediate vicinity. Consequently, if the molecular environment of an atom or molecule within a sample is altered, then its absorption or emission spectra may change. Spectroscopy can therefore be used to monitor physicochemical changes that result in an alteration in the molecular environment of atoms and molecules, e.g., protein unfolding, solubilization, or aggregation.