Characterization and Measurement of Flavor Compounds
D o n a l d D. Bills, Editor U.S. Department of Agriculture C y n t h i a J . M u s s i n a n , Editor International Flavors and Fragrances Examines the sensory, chemical, and physical methods for characterizing and measuring flavor compounds. Highlights state-of-the-art instrumental techniques and their application to studies of flavor. Also covers sensory methods as well as new methods for extracting, derivatizing, and manipulating flavor compounds. CONTENTS Sensory Evaluation of Food Flavors · Substances That Modify the Perception of Sweetness · Sensory Responses to Oral Chemical Heat · Analysis of Chiral Aroma Components in Trace Amounts · New Analytical Method for Volatile Aldehydes · The Use of HighPerformance Liquid Chromatography in Flavor Studies · Capillary Gas Chromatographic Analysis of Volatile Flavor Compounds · High-Resolution Gas Chromatography-Fourier Transform IR Spectroscopy in Flavor Analysis · Tandem Mass Spectrometry Applied to the Characterization of Flavor Compounds · Automated Analysis of Volatile Flavor Compounds · Supercritical Fluid Extraction in Flavor Applications Developed from a symposium sponsored by the Flavor Subdivision of the Division of Agricultural and Food Chemistry of the American Chemical Society ASC Symposium Series No. 289 185 pages (1985) Clothbound LC 85-22913 ISBN 0-8412-0944-8 US & Canada $42.95 Export S51.95 Order from: American Chemical Society Distribution Dept. 89 1155 SixteenthSt.,N.W. Washington, DC 20036 or CALL TOLL FREE 800-424-6747 and use your credit card!
Figure 2 . Cutaway schematic of a Cassegrainian lens
the mathematical technique that served to convert the output of the Michelson interferometer, an interferogram, into a spectrum. In the 1920s, W. W. Coblentz, working at the National Bureau of Standards, showed that IR spectra of compounds were characteristic physical properties of these compounds and could be used for their identification. At about the same time, C. V. Raman, in India, showed that Raman spectra were similarly useful. The Raman effect, because of its inherent weakness, did not become a generally effective method of studying substances until after the development of the laser, pioneered by C. H. Townes. Both IR and Raman spectroscopy received a final impetus and advance through their coupling with the modern digital computer, fathered by von Neumann. Only after all these major developments (and a host of minor advances) had occurred were IR and Raman ready to be coupled with the optical microscope, an instrument whose uses had been developed in the seventeenth century by van Leeuwenhoek. The final result is two complementary methods for identification of molecular species at the picogram level with promise of extension in the near future to the femtogram level. To study these techniques, their complementarity and application, the
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Molecular Microspectroscopy Laboratory (MML) at Miami University was designed and developed to perform research and method development in this new area. This laboratory became operational in early 1985. Although there are papers scattered in the literature that are concerned with specific applications of IR or Raman microspectroscopy, there appear to be few general reports concerning their capabilities. Several samples of the work performed in the MML, covering a broad range of interests, follow. It is hoped that they will serve to give the reader a suitable introduction to the possibilities of the techniques and a feeling for the developments to be expected in the near future. Instrumentation A few general principles with respect to the two methods are worth noting. Raman spectrometry is normally carried out in the visible region of the spectrum, and thus normal microscopes, with the usual glass optics, are quite satisfactory for coupling to the spectrometer. Because the source for Raman spectrometry must be monochromatic, an argon ion laser is typically used. It should be noted that the power requirements of the laser are not very high. Although the systems typically use beam splitters, which transfer a relatively small
