Volatile and semi-volatile compounds in flavoured hard seltzer beverages: comparison of high-capacity sorptive extraction (HiSorb) methods

The change in consumer behaviour towards healthier lifestyles since the Covid-19 pandemic has seen a steep rise in popularity of low-calorie, low-sugar food and beverage alternatives, like flavoured hard seltzers. In this study, a fully automated, high-capacity sorptive extraction (HiSorb) technique, coupled with gas chromatography–mass spectrometry (GC–MS), was developed to investigate volatile and semi-volatile organic compounds (VOCs and SVOCs) used for flavouring of hard seltzers. As part of methos optimisation we trialled various sample preparation protocols and compared extraction via direct immersion vs. extraction from the headspace. The best headspace and immersive techniques were then further analysed in a ‘stacked’ extraction, whereby extracts from both were collected onto a focusing trap and fired to the GC to produce a single chromatogram. HiSorb probes with 4 alternate phases were compared: Polydimethylsiloxane (PDMS), divinylbenzene/PDMS (DVB/PDMS), carbon wide range/ PDMS (CWR/PDMS) and a triple phase (DVB/CWR/PDMS), with the DVB/PDMS phase proving to extract the highest number of compounds. The DVB/PDMS probe was further applied to a study of four berry/cherry flavour hard seltzer drinks, produced by 4 different leading commercial brands, with 64 compounds extracted and identified. Chemometrics were able to distinguish each brand's flavour profile by detection of unique compounds, these having potential for use as quality and authenticity markers.