Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem Beer volatile fngerprinting at diferent brewing steps Vera Alves a , João Gonçalves a , José A. Figueira a , Laura P. Ornelas b , Ricardo N. Branco b , José S. Câmara a,c , Jorge A.M. Pereira a, ⁎ a CQM – Centro de Química da Madeira, Universidade da Madeira, Campus Universitário da Penteada, 9020-105 Funchal, Portugal b ECM – Empresa de Cervejas da Madeira, PEZO, Parque Empresarial Zona Oeste, 9304-003 Câmara de Lobos Funchal, Portugal c Departamento de Química, Faculdade de Ciências Exatas e da Engenharia da Universidade da Madeira, Campus Universitário da Penteada, 9020-105 Funchal, Portugal ARTICLEINFO Keywords: Beers Brewing process Volatile fngerprint VOMs HS-SPME/GC–MS ABSTRACT Volatile fngerprints of a lager beer were carried out throughout fve brewing steps to characterize the changes encompassing this process. Overall, 60 volatile organic metabolites (VOMs) were identifed by headspace solid- phase microextraction followed by gas chromatography mass spectrometry (HS-SPME/GC–MS). Specifc profles were observed at diferent brewing steps - aldehydes and furans dominate in wort, whereas the aliphatic esters and alcohols predominate in the following steps. Such variations can be assigned to specifc VOMs, as 3-me- thylbutanal (wort), ethyl alcohol and ethyl octanoate (fermentation, maturation and fltration), or ethyl alcohol and isoamyl acetate (fnal product). These VOMs can infuence the beer fnal favour. Ethyl alcohol contributes to its strong and pungent smell and taste, while isoamyl acetate adds intense ‘fruity’ and ‘banana’ odours. These beer volatile fngerprints constitute a valuable tool to obtain insights on the impact of each brewing step on the fnal product, being also very useful for certifcation purposes. 1. Introduction Beer is one of the most popular alcoholic beverages, being con- sumed in large amounts worldwide (with an annual production of al- most two billion hectolitres in 2018, according to the data available in statista.com). Is a complex mixture containing numerous favour-active volatile organic metabolites (VOMs) belonging to a diversity of che- mical families over a wide range of concentrations, polarities and vo- latilities. These VOMs refect the brewing process and have a strong infuence on the quality and character of the beer. Consequently, they are also important for beer characterization. Overall, beer favour re- sults from a complex combination of diferent aspects that give each brew distinctive profles. Such interferences result mainly from the in- gredients composition, the roasting malt and boiling wort conditions, the metabolites produced by yeast during fermentation as well as the ones produced by contaminant microorganisms and also the efects of oxygen and sunlight during product storage (Bettenhausen et al., 2018; Dong et al., 2015; Figueira et al., 2012; Olaniran, Hiralal, Mokoena, & Pillay, 2017; Preedy, 2009). Ingenericterms,thebrewingprocessinvolvesfourmainsteps,wort preparation, fermentation, maturation, and fltration and/or stabiliza- tion (detailed in the Supplementary Fig. 2). Before starting the brewing process, barley is artifcially induced to germinate and dried. This process, known as malting, allows the maturation of enzymes that di- gest complex starches in the grain into simple fermentable sugars. These sugars will be used later during mashing (Briggs, Boulton, Brookes, & Stevens, 2004; Eßlinger, 2009). Although malted barley is the most important cereal, wheat, wheat malt, corn, rice and millet are often used (Briggs et al., 2004; Eßlinger, 2009). The transition of malted barley to wort begins by grinding the grains. At this stage the grist is diluted, fltered and brought to boiling for one to two hours (Briggsetal.,2004).Inthisprocess,hopsorhop-derivedproducts,such as hop pellets or hop essential oils are added. Hops possess a char- acteristic favour and aroma that exert a strong infuence on the fnal product and so its dosage needs to be adjusted to the profle of the desired beer and integrated harmonically in the matrix during the beer maturation (Eßlinger, 2009). At the end of the boil, the resulting wort contains coagulated proteins or 'trub' and suspended fragments of hops https://doi.org/10.1016/j.foodchem.2020.126856 Received 18 November 2019; Received in revised form 28 March 2020; Accepted 17 April 2020 Abbreviations: DBV/CAR/PDMS, divinylbenzene/carboxen on polydimethylsiloxane; DMSO, dimethyl sulfoxide; DMS, dimethyl sulphide; ECM, Empresa de CervejasdaMadeira;GC/MS,gaschromatography–massspectrometry;GC-qMS,gaschromatography–quadrupolemassspectrometry;HS-SPMCE,headspacesolid- phase microcolumn extraction; IEC, ion extraction chromatogram; LLE, liquid–liquid extraction; RI, retention index; RSD, relative standard deviation; SBSE, stir-bar sorptive extraction; SDE, simultaneous extraction and distillation; SPE, solid-phase extraction; SPME, solid-phase microextraction; SVOMs, semi-volatile organic metabolites; VOMs, volatile organic metabolites ⁎ Corresponding author. E-mail address: jorge.pereira@staf.uma.pt (J.A.M. Pereira). Food Chemistry 326 (2020) 126856 Available online 25 April 2020 0308-8146/ © 2020 Elsevier Ltd. All rights reserved. T