Beer contains hundreds of organic ingredients, and the combination of these results in its unique aroma and flavour. Many of the aroma-active compounds come from hops, and monoterpenes (C10) and sesquiterpenes (C15) in particular provide much of the characteristic ‘bitterness’ of the finished beer.[1]
However, these compounds can span many orders of magnitude in concentration and may have very low odour thresholds, so robust and highly sensitive analysis is needed to assess the quality of the hops before brewing commences.
Traditionally, solid-phase micro-extraction (SPME) has been used to sample volatile organic compounds (VOCs) from foods and beverages. Although SPME is fast and simple, it can suffer from limited sensitivity and poor reproducibility, and can be prone to capillary effects that limit fiber lifetime when immersive sampling is used.
High-capacity sorptive extraction can tackle these issues, by providing a larger volume of PDMS stationary phase (65 μL compared to ~0.5 μL for SPME) that results in higher sample loadings. The probes are also robust and easily rinsed free of matrix for trouble-free immersive sampling of beer. Used in conjunction with secondary refocusing, this approach offers excellent sensitivity, as well as the ability to re‑collect a portion of the sample for repeat analysis in a fully automated workflow, using the Centri® platform from Markes International.
However, even when benefitting from the advantages of such systems, the aroma profiles of hops and beer are often highly complex. As a result, higherloading components can frequently mask important compounds (such as sulfur species that cause undesirable odour taints even at trace levels).
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