Aged Beer Research Articles

Valorization of Spent Hops from Dry Hopping for Bittering of Pilsener Style Beer

In the last decade production of dry hopped beers increased considerably. Dry hopping results in significant amounts of spent hop material (mixture of beer and hop vegetative matter), which is mostly regarded as waste and is discarded. During dry hopping polar (aroma) compounds are extracted into beer, while nonpolar compounds such as humulones largely remain in the spent hops. In this study, spent hops from local craft breweries were collected. They were analyzed towards dry matter (d.m.), surplus beer content, their concentration of humulones, and iso-humulones, and were then used as the sole source of bitterness in the production of Pilsener Style beer. It was found that humulone concentrations in spent hops ranged from 1 to 10.3% dry matter, which corresponds to retention rates of 28 to 94%. Wort and beer samples made from selected spent hop samples were analyzed using a range of physicochemical analyses, along with sensory evaluation of both fresh and aged beers. Beer analysis showed that the targeted bitterness (30 BU) was successfully achieved in most brews. Sensory analysis confirmed the good overall quality of spent hop beers as such and also in comparison with a reference brew using hop pellets. In summary, spent hops can be valorized by substituting hop pellets in the kettle, leading to reduced beer losses, savings on hop pellets, increased sustainability and hence reduction of production costs.

Modelling of beer sensory staleness based on flavour instability parameters

Why was the work done: The deterioration of the flavour of fresh beer is challenging for the brewing industry. Despite extensive research on flavour instability, the focus has centred on a limited set of parameters, rather than taking a broader approach.
 How was the work done: in this study, the intent was to produce a flavour stable beer. Using a low kilning temperature, malt of low staling potential was used in combination with best brewing practice to produce three batches of unpasteurised top fermented pale beers at a pilot scale. Forty-three markers were analysed in the fresh and aged beers (30°C for 15, 30, 60 and 90 days). Staleness was evaluated by a trained sensory panel and multivariate data analysis was used to explore how the markers contribute to staleness.
 What are the main findings: Repeatability was achieved between replicate brews and, subsequently, staling. Polyphenols, haze, total reactive antioxidant potential (TRAP), iso-α-acids, colour, furfural, 2-methylpropanal and 2-methylbutanal showed a strong correlation with staleness. Staleness doubled after 60 days of storage at 30°C, despite volatile aldehydes remaining below their sensory thresholds, implying a synergistic effect of carbonyls contributing to staleness. A Partial Least Square (PLS) model was established, modelling the sensory staleness from 2-methylpropanal, furfural, TRAP and the trans-/cis-iso-α-acids ratio.
 Why is the work important: The staling phenomena could be reproduced in beers from parallel brewing trials with only minor variations. The four parameters in PLS modelling indicate that beer staling involves a combination of oxidative and non-oxidative pathways.

Дослідження ароматичного комплексу та органолептичних характеристик витриманих пивних дистилятів

Дослідження ароматичного комплексу та органолептичних характеристик витриманих пивних дистилятів

A Rapid Method to Predict Beer Shelf Life Using an MS-Based e-Nose

A rapid and efficient technique was applied, which used an electronic nose based on a mass detector (MS-based e-nose) combined with headspace solid-phase microextraction sampling and chemometric tools to classify beer samples between fresh and aged and between samples contained in aluminium cans or glass bottles, and to predict the shelf life of beer. The mass spectra obtained from the MS-based e-nose contained details about volatile compounds and were recorded as the abundance of each ion at different mass-to-charge (m/z) ratios. The analysis was performed on 53 naturally aged samples for eleven months without light and with a controlled temperature of around 14 °C ± 0.5 °C. Principal component analysis (PCA) was performed on the data and showed a grouping of samples between fresh and aged. Partial least square discriminant analysis (PLS-DA) allowed the discrimination of fresh from aged beers but could not discriminate between the samples according to the type of packaging. Finally, partial least squares regression (PLSR) proved to be an effective method for predicting beer shelf life.

Why Oxidation Should Be Still More Feared in NABLABs: Fate of Polyphenols and Bitter Compounds

Nowadays, non-alcoholic (NAB) and low-alcoholic beers (LAB) still significantly suffer from staling defects when fresh, partially due to absence of ethanol as antioxidant. In the current work, the fate of flavan-3-ols (monomers, dimers, and trimers) and bitter compounds (isohumulones, humulinones, etc.) of 11 commercial NABLABs available on the Belgian market was monitored through one year of aging at 20 °C in the dark. Fresh NABLABs contained variable flavan-3-ols and bitter compounds levels (between 3.0–10.0 mg/L and 8.0–39.0 mg/L, respectively), depending on different technological processes used. Chill haze and color were also investigated as potential oxidation markers of fresh and aged beers. Surprisingly, contrary to conventional beers, the oligomers’ concentration (dimer and trimer procyanidins) exhibited a strong correlation (R2 = 0.95) with chill haze before aging, suggesting prematured oxidation of the samples. After a year of storage, significant degradation occurred as for regular dry hopped beers (process very sensitive to oxidation), only 27% remaining for flavan-3-ol dimers and an average 16% for trans-isohumulones. Oxidation risk appears here as the main weakness of NABLABs, which could be probably improved by spiking very efficient antioxidants.

Impact of temperature during beer storage on beer chemical profile

Aiming to gain insights into the impact of storage conditions on the chemical profile of beer samples, changes on the relative amount of several chemical classes of compounds was monitored. The influence of storage conditions was statistically discerned using the hierarchical cluster analysis complemented by heatmap date visualization. Aldehydes, furanic compounds and esters showed a clear role in beers stored at 37 ± 1 °C (contribution >1, as obtained in the heatmap data visualization). The reaction rate constant and temperature dependence was well described by the Arrhenius equation for these compound classes, for which the reaction rate increased with increasing temperatures. The rate of development of furanic compounds, aldehydes and esters showed to be almost 140, 90 and 20 times higher in beers stored at higher temperatures (37 ± 1 °C) when compared to beers stored at 4 ± 1 °C, respectively. These results indicate that temperature was the main parameter contributing to the major changes in beer chemical profile. Through olfactometric analysis, the major difference was found in aged beers, both naturally and forced aged, where the prevalence of sweet and papery aroma notes were noticed, linked to the development of β-damascenone and E-2-nonenal, respectively.

Gas-Diffusion Microextraction (GDME) Combined with Derivatization for Assessing Beer Staling Aldehydes: Validation and Application.

In this work, a gas-diffusion microextraction (GDME) methodology was optimized and validated for the analysis of selected staling aldehydes (furfural (FURF), 2-methylpropanal (2-MP), 2-methylbutanal (2-MB), 3-methylbutanal (3-MB), and acetaldehyde (ACET)) during natural and forced aging of beer. The methodology was optimized considering time, temperature of extraction, and derivatizing agent. Using 4-hydrazinobenzoic acid (HBA) as a derivatizing agent, the performance of the method was evaluated by assessing several parameters such as detection limits (ranging from 1.2 to 1857.7 µg/L for 2-MB and ACET, respectively), quantification limits (ranging from 3.9 to 6192.4 µg/L for 2-MB and ACET, respectively), recoveries (higher than 96%), intraday and interday precisions (lower than 3.4 and 9.2%, respectively), and linearity (r2 ≥ 0.995). During beer aging, higher content of Strecker aldehydes and FURF were found, while no significant variations in ACET levels were observed. In general, the aldehydes content assessed for beers stored at 37 ± 1 °C for 7 and 14 days mimics that observed for beers stored at 20 ± 2 °C for 3 and 6 months, respectively. Lower temperatures of storage (4 ± 1 °C) delayed the development of staling aldehydes. Based on PCA analysis, the content of staling aldehydes and beer color were responsible for 91.39% of the variance among the analyzed samples, and it was demonstrated that these are key parameters to discriminate fresh from aged beers. The results herein presented showed that the proposed analytic methodology is a valuable strategy for the characterization and quantification of important staling aldehydes in beer with a potential application in the quality control of beer during storage.

Effects of adding spices with antioxidants compounds in red ale style craft beer: A simplex-centroid mixture design approach

The growing demand for authentic products that provide sensory characteristics combined with health benefits has been the focus of current studies. This study developed a Red Ale style craft beer with spices such as turmeric (T), black pepper (P) and aroma hops (H), used isolated or in mixtures. A mixture design was employed to evaluate the total phenolic compounds and the antioxidant activity in the green and aged beers formulations. The spice extracts influenced the product's shelf-life. The addition of spices into the beers did not affect the physicochemical parameters that classify the Red Ale style, according to the hierarchical cluster analysis, except for aroma hops. A multiresponse optimization approach simultaneously maximized the antioxidant activity and the phenolic compounds in beers. The ideal formulation obtained for green beers was 25% T and 37.5% P and H; for aged beers, the formulation was 50% T, 20% P and 30% H.

Monitoring the evolution of free and cysteinylated aldehydes from malt to fresh and forced aged beer

During storage, beer staling coincides with a gradual increase in the concentrations of aldehydes resulting in the appearance of undesirable flavours. Cysteinylated aldehydes, also referred to as 2-substituted 1,3-thiazolidine-4-carboxylic acids, have been proposed as potential precursors of this increase. This study aimed to further understand the origin of aldehydes in aged beer, by monitoring both free and cysteinylated aldehydes throughout the brewing process, from the raw materials until the stored product. Quantification of free and cysteinylated aldehydes was performed for two different brews via headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS), respectively. All selected marker aldehydes were quantified in malt, wort, and the resulting fresh and aged beer samples. Cysteinylated aldehydes were quantifiable in malt and up to the wort boiling phase. The highest levels of free aldehydes were found in malt, whereas cysteinylated aldehydes showed highest levels at mashing-in pointing to their formation during both malting and subsequent mashing-in. During beer ageing, an increase in all free aldehydes was measured. In particular, a rise in 2-methylpropanal and furfural is most striking. Although the presented experimental data obtained on malt and brewery samples do support the concept of bound-state aldehydes, cysteinylated aldehydes cannot be consider as the cause of increasing levels of staling aldehydes during beer ageing.

Breeding and brewing quality of the Canadian malting barley variety 'CDC Goldstar' lacking lipoxygenase-1.

Various types of malt quality profiles have been investigated to benefit the North American brewing industry. Herein, we report the development and brewing quality of the hulled, two-row malting barley (Hordeum vulgare L.) variety ‘CDC Goldstar’ lacking lipoxygenase-1 (LOX-1-less). This new variety offers a novel malt type for the improvement of beer flavor stability. The agronomic performance of ‘CDC Goldstar’ was tested in the Western Cooperative Two Row Barley Registration Trials during 2013–2014. In addition to high lodging tolerance, the new variety showed 6% higher yield than the current leading variety ‘CDC Copeland’. The malt quality of ‘CDC Goldstar’ showed higher diastatic power and lower wort β-glucan content than ‘CDC Copeland’ and controllable proteolytic modification (soluble nitrogen and Kolbach Index). Pilot- (100 L) and commercial-scale (5,000 L) brewing trials were conducted using ‘CDC PlatinumStar’, another LOX-1-less variety with a low enzymatic profile, as the control variety. Absence of the LOX-1 trait from ‘CDC Goldstar’ maintained trans-2-nonenal levels in aged beers as low as those in other LOX-1-less varieties without affecting major beer parameters, such as ester and aldehyde content or foam stability. The newly developed ‘CDC Goldstar’ malting barley provides added value for the beer industry and consumers.

Evaluation of multi-starter S. cerevisiae/ D. bruxellensis cultures for mimicking and accelerating transformations occurring during barrel ageing of beer

During beer ageing, endogenous barrel microbes grow spontaneously and transform wort/beer composition, being Dekkera bruxellensis and Saccharomyces cerevisiae among the main contributors to the chemical and sensory profile of aged beer. This work aims at the application of multi-starter cultures to mimic and accelerate biological modifications occurring during barrel ageing of beer, in controlled fermentation processes. Co-cultures of D.bruxellensis/S.cerevisiae were conducted under conditions commonly found in barrel aged beer production: different pitching rates, high glucose concentration and presence of ethanol and wood extracts. Selective pressures and competition between yeasts influenced microbial growth and metabolite production, namely ethanol, acetic acid and target volatile compounds (esters, alcohols, terpenols, volatile acids and volatile phenols). Metabolic profiles of co-cultures combined traits of both species, and differed from those of pure cultures. Lastly, multi-starters were successfully applied in combination with wood in a controlled and accelerated fermentation process for mimicking barrel ageing transformations.

Instability of Hop-Derived 2-Methylbutyl Isobutyrate during Aging of Commercial Pasteurized and Unpasteurized Ales

The current article is concerned with the instability of 2-methylbutyl isobutyrate (2-MBIB) throughout beer storage. 2-MBIB is the primary ester of hops and HS-SPME-GC-MS/MS analysis of 135 commercial ales confirmed that 2-MBIB is also one of most abundant hop-derived volatiles in ale. To investigate 2-MBIB stability during beer aging, eleven domestic ales with initial 2-MBIB levels ranging from 10 − 311 µg/L were analyzed across freshly packaged, naturally and forced aged beer. Upon storage, 2-MBIB concentrations in all ales decreased remarkably. After 24 weeks at 20 °C the tested ales lost 80% of their initial 2-MBIB concentration on average. At 4 °C, which is considered an ideal beer storage temperature, the average reduction was still 60%. Overall, the lowest 2-MBIB reduction was found in pasteurized ales, indicating that 2-MBIB decrease is driven by chemical and enzymatic reactions. The losses of 2-MBIB appear to be a significant contributor to the chemical instability of hoppy ales.

Covalent Protein-Polyphenol Bonding as Initial Steps of Haze Formation in Beer

Beer subjected to forced aging by five (Medium) or ten (High) heat/chill cycles (60 °C 48 h/0 °C 24 h) showed increased turbidity from 5.4 ± 0.4 EBC units without forced aging to 12.9 ± 0.7 and 48 ± 2 EBC units for Medium and High forced aged beers, respectively. The particle size diameter increased from 100–200 nm to 10–30 µm. The colloidal changes were associated with modifications of the low molecular weight fraction (∼1 kDa), which were found to increase in the soluble part of the beer as identified by size exclusion chromatography. Polyphenol analyses by liquid chromatography and mass spectrometry showed significant losses of gallic acid, hydroxyphenyllactic acid, salicylic acid, chlorogenic acid, vanillic acid, epicatechin, pyrocatechuic acid, ferulic acid, and luteolin during the forced aging, indicating that these phenolic compounds took part in the colloidal changes, proposedly upon polymerization into tannins. Gel electrophoresis coupled with staining by nitroblue tetrazolium indicated polyphenol modification of all proteins and especially LTP1 (lipid transfer protein 1). It is proposed that the di- and tri-hydroxyl phenolic compounds upon oxidation to quinones react with protein nucleophiles of especially LTP1 to generate the initial covalent bonds, which eventually leads to larger insoluble permanent haze particles.

The relationship between flavour instability, preference and drinkability of fresh and aged beer

The relationship between flavour instability, preference and drinkability of fresh and aged beer

Application of chitooligosaccharides as antioxidants in beer to improve the flavour stability by protecting against beer staling during storage.

To improve beer flavour stability by adding chitooligosaccharides that prevent formation of staling compounds and also scavenge radicals in stale beer. Chitooligosaccharides, at 0.001-0.01%, inhibited the formation of staling compounds in forced aged beer. The formation of 5-hydroxymethylfurfural, trans-2-nonenal and phenylacetaldehyde were decreased by 105, 360 and 27%, respectively, when compared with those in stale beer without chitooligosaccharide addition. The capability of chitooligosaccharides to prevent staling compound formation depended on their molecular size (2 or 3kDa). The DPPH/hydroxyl radical scavenging activity in fresh beer significantly lower than that in forced aged beer in the presence of chitooligosaccharides. When compared with stale beer without added chitooligosaccharides, the radical scavenging activity could be increased by adding chitooligosaccharides to forced aged beer. Chitooligosaccharides play an active part in the prevention of beer flavour deterioration by inhibiting the formation of staling compounds and increasing radical scavenging activity.

How sotolon can impart a Madeira off-flavor to aged beers.

4,5-Dimethyl-3-hydroxy-2(5H)-furanone or sotolon is known to impart powerful Madeira-oxidized-curry-walnut notes to various alcoholic beverages. It has been much studied in oxidized Jura flor-sherry wines, aged Roussillon sweet wines, and old Port wines, in which it contributes to the characteristic "Madeira-oxidized" aroma of these beverages. No scientific paper describes how sotolon might be involved in the Madeira off-flavor found in aged beers. The specific extraction procedure applied here allowed us to quantify this lactone in 7 special beers, at levels sometimes well above its threshold (from 5 to 42 μg/L after 6, 12, 18, and 24 months of natural aging, while unquantifiable in fresh beer). Investigation of spiked beers led us to highlight the key role of pro-oxidants and acetaldehyde. Addition of ascorbic acid without sulfites should be avoided by brewers, as the former would intensify sotolon synthesis. Acetoin, a beer fermentation byproduct, also emerged as possible precursor in beer when combined with serine.

Influence of Different Hop Products on the cis/trans Ratio of Iso-α-Acids in Beer and Changes in Key Aroma and Bitter Taste Molecules during Beer Ageing

Isomerization of α-Acids from hops can result in different ratios of cis-to trans-iso-α-acids. In contrast to oxidative degradation processes, the conversion of iso-α-acids to tri- and tetracyclic compounds during beer ageing is only possible in the trans form. Therefore, it might be an advantage to use pre-isomerized hop products in order to maximize the cis form in beer. For this study, beers conventionally hopped with regular pellets were compared with beers produced with isomerized pellets and isomerized extracts. In addition, inline pre-isomerization was investigated as another alternative. The four variants were produced in a pilot brewery. Bottled beers were stored at 5 and 28°C. Analysis of fresh and aged samples after 4, 8, and 12 months was focused on bitter compounds (HPLC-MS/MS) and on volatile aroma compounds (GC-MS/MS). Beers produced with isomerized hop products showed higher ratios of cis- to trans-iso-α-acids, and their amounts of degradation products of trans-iso-α-acids were accordingly lower after ageing. However, all of the four types of beers hopped in different ways showed very similar profiles of volatile aroma compounds even during ageing. Moreover, sensory evaluation of aged beers gave no preference for the variations with pre-isomerized hop products.

NIR spectroscopy coupled with multivariate computational tools for qualitative characterization of the aging of beer

This work studies the potential use of near infrared (NIR) spectroscopy for the qualitative analysis of different beer types during the aging process. For this purpose, some computational tools (Principal Component Analysis (PCA), K Nearest Neighbours (KNN), Linear Discriminant Analysis (LDA), Stepwise LDA (StepLDA), Genetic Algorithms (GA) and Gram–Schmidt supervised orthogonalization (SELECT)) were employed over the beer fingerprints obtained to characterize the aging stages as well as beer types. The selection of useful variables has been performed by means of SELECT, StepLDA, and GA. Based on the results, the two alcoholic beers and the two non-alcoholic beers heavily overlap but the aging treatments were clearly discriminated. However, the NIR coupled with the multivariate computational tools has demonstrated a good capability to discriminate and classify the aged beers satisfactorily in such a way, for all aging treatments, high classification accuracies were found.

Occurrence of the ribes odorant 3-sulfanyl-3-methylbutyl formate in aged beers

2-Sulfanyl-3-methylbutyl formate and acetate were synthesized without purification steps, quantified with a pulsed flame photometric equimolar detector, and characterized by comparison with commercially available 3-sulfanyl-3-methylbutyl formate and acetate (retention indexes, mass spectra, odour descriptors, and intensities). Both formates exhibited a typical ribes flavour, in contrast to both acetates, which were much more piquant. The sensorial threshold of 3-sulfanyl-3-methylbutyl formate was much lower (57 ng/l in beer, BE-GC-LoADS = 0.0006 ng) than those measured for the three other esters. Only 3-sulfanyl-3-methylbutyl formate was perceived at the sniffing port in beer extracts. Concentrations up to 1230 ng/l were measured in pilot beers after 1 month at 20°C, although the compounds are rarely detected in commercial beers with highly oxygen-protected bottling. Accelerated ageing in the presence of oxygen confirmed the key role of oxygen. Copyright © 2013 John Wiley & Sons, Ltd.

Identification of a Protein with Antioxidant Activity that is Important for the Protection against Beer Ageing

This study was carried out with fresh Australian lager beer which was sampled directly off the production line, the same samples aged for 12 weeks at 30 °C, and the vintage beer which was kept at 20 °C for 5 years. Characteristic Australian lager flavour was maintained in the fresh and vintage beers but was lost in the aged beer. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and free thiol group labelling analyses of beer proteins found that this flavour stability correlated with the presence of an unknown 10 kilodaltons (kDa) protein with a higher level of free thiols. The protein was purified by size-exclusion chromatography, then peptide sequencing and database matching identified it as the barley lipid transfer protein (LTP1). Further characterisation using diphenylpicrylhydrazyl (DPPH) free radical scavenging and a Saccharomyces cerevisiae-based antioxidant screening assay demonstrated that the LTP1 protein was active in DPPH reduction and antioxidant activity. The absence of free thiol in the aged beer indicates that the thiol functional groups within the LTP1 protein were saturated and suggests that it is important in the flavour stability of beer by maintaining reduction capacity during the ageing process.