Selected ion flow tube - mass spectrometry: detection and real-time monitoring of flavours released by food products

Abstract

This paper is concerned with the application of our selected ion flow tube mass spectrometric analytical method (SIFT-MS) to the analysis of the complex aromas of some food products. This SIFT/MS chemical ionisation technique, to date mostly applied to breath analysis in medicine and health and safety practice, involves the use of pre-selected H 3 O , NO and O 2 ions to 'soft ionise' the volatile organic compounds (VOCs) that constitute complex mixtures such as food aromas. The kinetics involved are well-defined thus allowing quantification of several trace gases simultaneously in an air sample in real time without the need for pre-calibration. In order to facilitate the interpretation of the spectra obtained for complex mixtures by SIFT/MS we have carried out detailed studies of the reactions of these three ion species with a wide variety of organic compounds including many alcohols, aldehydes, ketone, esters and organosulphur compounds. A large kinetics database has thus been created and general patterns of reactivity are seen which are shown to be invaluable for SIFT/MS analyses. Thus, the SIFT mass spectra for some specific food flavours and for the VOCs emitted by cut onion, crushed garlic and ripe banana are presented and interpreted. Finally, the temporal variations in the concentrations of some of the VOCs emitted by these food products, obtained in real time using SIFT/MS in the selected ion monitoring mode, are also presented, which demonstrate the value of this analytical technique in food research.

Rapid detection of lipid oxidation in beef muscle packed under modified atmosphere by measuring volatile organic compounds using SIFT-MS

“…This is the case of selected ion flow tube mass spectrometry (SIFT-MS; Smith & Španěl, 2005;Španěl & Smith, 1999) that it is based on the chemical ionization of a gas sample using specific, selected precursor (reagent) positive ions. SIFT-MS allows the real time quantification of a volatile compound in humid air without external calibration.…”

Selected ion flow tube, SIFT, studies of the reactions of H3O+, NO+ and O2+ with some biologically active isobaric compounds in preparation for SIFT-MS analyses

“…Since reactions (6)-(8) occur in parallel, then measurements of the count rates of each of the ions involved in the ion chemistry contain the information required to calculate the three-body rate coefficients, k MH+ , of the hydration reaction (6). Essentially, this involves comparison of the efficiencies of reactions (6) and (7) expressed by a dimensionless association efficiency coefficient, A eff , [14] describing how efficiently the product ions form hydrates with respect to H 3 O + .…”

“…Since its inception, selected ion flow tube mass spectrometry, SIFT-MS, [1][2][3] has been applied to the analysis of many gas phase media, notably humid exhaled breath and urine headspace, aimed at clinical diagnosis and therapeutic monitoring [4], bacterial cultures in medicine [5] and food and foods flavours [6,7]. In essence, this often requires the detection and quantification of a wide range of volatile organic compounds, VOCs, present in humid air at concentrations down to parts-per-billion by volume, ppbv.…”

Real Time Detection of Aroma Compounds in Meat and Meat Products by SIFT-MS and Comparison to Conventional Techniques (SPME-GC-MS)

“…In the last few years the innovative selected ion flow tube mass spectrometry (SIFT-MS) analytical technique [1,2] has been used to analyse the volatile organic compounds emitted by foods in real time [3,4]. However, few analyses have focused on meat and meat products [5,6,7], but recently Olivares et al, [6] have investigated the correlations between SIFT-MS and GC-MS analyses of the volatiles emitted by fermenting sausages.…”