QUALITY-CONTROL OF FOOD WITH NEAR-INFRARED-EXCITED RAMAN-SPECTROSCOPY

The former considerable handicap of Raman spectroscopy in the visible range, the disturbing fluorescence of impurities, has now been eliminated: Raman spectra are excited by light quanta of the near-infrared range; their energy, however, is too small to excite fluorescence spectra. Now Raman spectroscopy can be applied to many'real world samples', to quality control of raw material, to production and product control. This paper gives examples of the application to food analysis. Many problems can be solved without a special sample preparation, even by using fibre bundles on-line at the sample site, in containers and in real time for production control. The configuration and amount of C = C bonds in lipids can be determined directly, also the nature and amount of proteins and carbohydrates, and the composition of food products. Natural and synthetic colours, flavours and vitamins can be detected on TLC plates, especially if Raman scattering is enhanced by resonance. Traces of distinct compounds can be detected by the SERS technique (the surface-enhanced Raman spectroscopy). The powerful new tool of analytical chemistry promises many useful applications and the replacement of time-consuming traditional methods.