Mass spectrometry in food analysis.

Abstract

Foods are complex mixtures of sugars, oils, proteins, vitamins, polyphenols, etc., which develop a myriad of flavour and aroma constituents during ripening and cooking. Agricultural and technological residues from pesticides and additives further complicate these mixtures where quantities of individual compounds range from several per cent to sub-part per billion levels. Mass spectrometry has proved an excellent tool for characterization and estimation of food components because of its high sensitivity and specificity. Gas chromatography mass spectrometry undoubtedly provided the major opening for mass spectrometry in food applications: natural volatiles and derivatized polar isolates were readily analysed even in mixtures with over 100 constituents. Organoleptically important minor components were identified in many foods and were monitored as a function of ripeness or cooking conditions. With computer treatment and library facilities, much gas chromatographic mass spectrometric work in flavour and aroma chemistry is now routine. Selected ion monitoring and multi-peak monitoring are used with electron impact, chemical ionization or negative chemical ionization to quantify pesticides, nitrosamines, mycotoxins and other contaminants in part per billion amounts. Isotope mass spectrometry can distinguish natural food flavourings from synthetic chemical equivalents, and can thus be used to detect adulteration. For the future there is room for applications of chemical ionization and negative chemical ionization in trace identification, for liquid chromatography mass spectrometry and collision activated decomposition in mixture analysis, and for new ionization techniques like desorption chemical ionization, laser desorption and fast atom bombardment in the investigation of highly polar solids and biopolymers: polypeptides, polysaccharides, polyphenols, nucleosides and nucleotides, etc. However, the adoption of new mass spectrometric methods by food analysts will ultimately depend on their ease of operation.