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D. CARDIN1, T. Robinson1, and C. Casteel. (1) Entech Instruments, Inc., 2207 Agate Ct., Simi Valley, CA 93065 Headspace analysis by GCMS continues to be a commonly used technique for quantifying flavor compounds in foods and beverages. In order to perform GCMS analysis of headspace compounds down to olfactory detection limits, the headspace must be concentrated as much as 500 fold or more. Most static headspace autosamplers inject only 3 mls or less into the GC, rather than the needed 100-1000 mls. Purge & Trap has been shown to be less effective at recovering the entire range of headspace compounds due to the strong adsorbents used and long sample flow paths. Finally, SPME is known to over-express heavier compounds while being subject to carryover. A new analytical technique called Pulsed Dynamic Headspace (PDH) has been developed to address the limitations of previous headspace methods. PDH uses larger sample containers providing up to 400cc of headspace for introduction into a trapping system.. Sample is drawn out of the headspace until the pressure reaches 3-5 psi below atmospheric, at which time the sample container is repressurized with UHP nitrogen through a fritted sparger that is either submerged or kept above sample level. Alternate sparging and sample extraction allows up to 1000 mls or more of headspace to be analyzed if needed. The sample containers are preheatable up to 170 deg. C, although heating is not needed to reach olfactory LODs due to the large sample volumes utilized. Preconcentration of the headspace is performed using a means to best preserve target headspace compounds, using either cryogenic cold trapping or mild adsorbents (PDMS coated glass beads + Tenax) prior to rapid injection onto a capillary GC column. Recovery of low level sulfur off-flavor compounds and other thermally labile compounds will be demonstrated in several foods and beverages.
Session 35, NEW PRODUCTS & TECHNOLOGIES: Innovations in processing and functional ingredients
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