Volatile fingerprinting differentiates diverse-aged craft beers
Introduction
Ageing of beverages in oak barrels is a common practice and is widely recognized for improving stability and organoleptic properties of the final product. During contact, several phenomena occur which impact beverage composition, namely the extraction of wood compounds, evaporation of beverage volatile compounds, oxidation of compounds in the beverage, and reaction between wood and beverage components (Mosedale & Puech, 1998). Extraction of volatiles from oak barrels depends mainly on wood extractible content, contact time, cellar conditions and beverage composition (Chira & Teissedre, 2014). Barrel usage is a crucial factor for ageing. The pool of extractable oak compounds is finite and the rate and amounts of compounds extracted diminish as the barrel is used in successive years (Wilkinson, Li, Grbin, & Warren, 2013). Furthermore, casks also retain compounds from the beverages aged in them, due to sorption of beverages components. As shown, oak wood retains compounds from the aged beverages, which can be transferred from one beverage to another through the reuse of the cask (Coelho, Domingues, Teixeira, Oliveira, & Tavares, 2019). Presence of lees in the cask can also take part on enhancing sensorial characteristics of alcoholic beverages, leading to higher body and aroma complexity as acknowledged in wine production (Del Barrio-Galán, Pérez-Magariño, & Ortega-Heras, 2011). Therefore, volatile composition of the aged beverage is influenced not only by the previously referred reactions occurring in the barrel but also by transference of compounds from one matrix to another, with the barrel posing as a vector for carrying such compounds and aromatic properties. Additionally, when envisaging beverages such as wine or beer, biological transformations occur during barrel ageing which furthermore modify chemical and sensory properties. Casks are often populated with microorganisms that alter significantly the beverage composition. Bacteria, such as Lactobacillus sp. and Enterobacter sp. and wild yeasts such as Brettanomyces sp., Debaryomyces sp. and Candida sp. can be found in wood and wine barrels with impact on beverage composition (Spitaels et al., 2014). Whilst mainly considered as spoilage organisms responsible for off-flavor production in wine, an increasing number of authors report that these endogenous microbes can add beneficial (or at least interesting) aromas that increase the flavor complexity of fermented beverages. On this field, Brettanomyces sp. strains are rising in importance, due to the ability to produce volatile compounds that enhance sensory properties of beer (Serra Colomer, Funch, & Forster, 2019). Several beer styles traditionally produced by fermentation in barrel rely on typical Brettanomyces sp. flavors such as seen for Lambic beers (Steensels et al., 2015) and Belgian red-brown acidic ales (Snauwaert et al., 2016).
With an increasing market which strives for innovative specialty products, mainly in craft beer, barrel ageing has been applied at great extent. Variables such as wood type and origin, presence of lees, resident barrel microbiota and ageing conditions lead to a large number of possible combinations to be performed. With such extent of variables to be manipulated and taking into account the multitude of compounds involved in beer sensory characteristics, ageing results are often unpredictable lead to heterogeneous products in regard to their chemical composition and sensory characteristics. In the case of wine, which has also complex composition, fingerprinting methodologies have been applied as omics tools for the discrimination, identification and quality control of dissimilar samples (Laaks, Letzel, Schmidt, & Jochmann, 2012) and for the investigation of the importance and effect of wine volatiles (González Álvarez, González-Barreiro, Cancho-Grande, & Simal-Gándara, 2011).
The aim of this work was the application and evaluation of volatile fingerprinting along with multivariate analysis as a tool to discriminate and characterize differences in barrel diverse-aged beers.
Section snippets
Samples
Beer samples were kindly provided by “Fermentum – Engenharia das Fermentações Lda.”, originating from “Letra” craft brewery. All samples originated from the same Belgian Dark Strong Ale wort with a specific gravity of 21 in the Plato scale (°P), leading to a beer with bitterness (IBU) of 27 and ethanol concentration, by volume, of 9%. Wort was fermented with Saccharomyces cerevisiae 1762 Belgian Abbey II (Wyeast Laboratories Inc.), pitched according with the instructions of the supplier, with
Results and discussion
Analysis and characterization of beers was conducted in order to highlight differences between ageing strategies and their corresponding impact on chemical profile. As seen in Fig. 2, ethanol concentration in barrel aged beers was significantly higher when compared with the unaged beer. Firstly, contact with Port wine lees (previously aged in the same barrels) can provide additional ethanol, considering that fortified wines contain alcoholic strength by volume between 19% and 21% (Tredoux &
Conclusions
Characterization of the barrel aged beers allowed the determination of the chemical differences between the beer samples as well as the impact of barrel reuse on beer ageing. Such was seen for the absence or pitching of S. cerevisiae, where wort fermented in barrel by endogenous microflora related strongly with 4-ethylphenol and 4-ethylguaiacol in the volatile fingerprint (typical Brettanomyces/Dekkera metabolites), which was less noticeable for wort also fermented in cask but with yeast
Acknowledgements
This work had funding support of the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2019 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 – Programa Operacional Regional do Norte. Fermentum – Engenharia das Fermentações Lda. also participated in co-funding and supplying materials for this work.
References (34)
- et al.
Understanding wine sorption by oak wood: Modeling of wine uptake and characterization of volatile compounds retention
Food Research International
(2019) - et al.
Techniques for improving or replacing ageing on lees of oak aged red wines: The effects on polysaccharides and the phenolic composition
Food Chemistry
(2011) - et al.
Effect of size, seasoning and toasting in the volatile compounds in toasted oak wood and in a red wine treated with them
Analytica Chimica Acta
(2010) - et al.
Volatile components of Zalema white wines
Food Chemistry
(2007) - et al.
Relationships between Godello white wine sensory properties and its aromatic fingerprinting obtained by GC–MS
Food Chemistry
(2011) - et al.
Polysaccharides and lignin from oak wood used in cooperage: Composition, interest, assays: A review
Carbohydrate Research
(2015) - et al.
Aroma quality improvement of Chardonnay white wine by fermentation and ageing in barrique on lees
Food Research International
(2010) - et al.
Aroma compounds as markers of the changes in sherry wines subjected to biological ageing
Food Control
(2005) - et al.
Wood maturation of distilled beverages
Trends in Food Science and Technology
(1998) - et al.
C6-alcohols as varietal markers for assessment of wine origin
Analytica Chimica Acta
(2006)
Role of lees in wine production: A review
Food Chemistry
The raise of Brettanomyces yeast species for beer production
Current Opinion in Biotechnology
Microbial diversity and metabolite composition of Belgian red-brown acidic ales
International Journal of Food Microbiology
Brettanomyces yeasts - from spoilage organisms to valuable contributors to industrial fermentations
International Journal of Food Microbiology
The production of ethylphenols in wine by yeasts of the genera Brettanomyces and Dekkera: A review
Food Chemistry
Influence du bois sur certaines substances odorantes des vins
OENO One
Brewing : Science and practice
Cited by (19)
Pattern recognition techniques in food quality and authenticity: A guide on how to process multivariate data in food analysis
2023, TrAC - Trends in Analytical ChemistryVolatile terpenoid profiling in gin and beer – A targeted approach
2023, Journal of Food Composition and AnalysisBioactive compounds, antioxidant activities and flavor volatiles of lager beer produced by supplementing six jujube cultivars as adjuncts
2022, Food BioscienceCitation Excerpt :The total content of esters in final beers fermented by jujube supplementation was approximately twice of control beer. Octanoic acid, deriving from yeast metabolism during alcohol fermentation (Coelho et al., 2019), represented the major acid in final beers, except beers fermented with the addition of HT, GT, and JS. Two acids, namely isobutyric acid and heptanoic acid, appeared in final beers fermented by jujube supplementation, which are the sensory compounds related with butter, cheese and sour.
Evaluation of multi-starter S. cerevisiae/ D. bruxellensis cultures for mimicking and accelerating transformations occurring during barrel ageing of beer
2020, Food ChemistryCitation Excerpt :One example of specialty products are barrel aged beers, produced either by fermentation of wort in wood barrels or by storage of previously fermented beer in wood casks. During contact with wood several phenomena occur: wood compounds are extracted by the hydroalcoholic matrix (additive ageing), beverage compounds are adsorbed by wood (subtractive ageing), oxidative and polymerization reactions (chemical ageing) and, more importantly, a secondary fermentation takes part (biological ageing), transforming chemical and sensorial characteristics of the product (Coelho, Magalhães, et al., 2019). In most barrel aged beers, this secondary fermentation is the result of the spontaneous growth of microbial population, mostly endogenous to the barrel or populating the brewery atmosphere (Spitaels et al., 2014).
Development of a stir bar sorptive extraction method to study different beer styles volatile profiles
2019, Food Research InternationalCitation Excerpt :The volatile compounds determined in highest concentrations were 3-methyl-1-butanol followed by phenylethyl alcohol, presenting values in ale beers around 100 mg/L and 20 mg/L, respectively. Similar results were obtained by other authors that reported those compounds as the major volatile alcohols found in ale beers (Coelho et al., 2019). Comparing the different types of beers, on the one hand, some compounds such as ethyl isovalerate, α-terpinolene, linalool, hexanoic acid, or guaiacol were found in significant higher concentrations in ale beers, compared to the rest of beer styles.