Beer Staling Research Articles

Relationship among EPR oxidative stability and spectrophotometric parameters connected to antioxidant activity in beer samples

A relationship between EPR and spectrophotometric parameters related to beer staling and antioxidant activity, was identified. AUC (area under the curve), intensity at 150 min (T150), radical scavenging activity (RSA), total phenolic compounds (TPC), hydroxyl radical scavenging capacity (HRSC) and one parameter linked to staling degree of beers (thiobarbituric index, TBI) were related. Temperature was modified to find the proper working conditions for EPR spin-trapping experiments and it was found that it affected the kinetic of PBN adduct evolution. For the samples reaching a maximum intensity signal, the higher the heating temperature, the shorter the time interval needed to reach it. No linear relationship was detected among parameters obtained with EPR spin trapping experiments and RSA, TPC, TPI, and HRSC when correlating one parameter with another. On the contrary, a good linear relationship was found among AUC or T150 and a combination of RSA, TPC, TPI, and HRSC (R2 = 0.9562 and 0.9694, respectively). The goodness of fit increased to R2 = 1 when a combination of AUC and T150 was related to a combination of RSA, TPC, and TPI, and HRSC.

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.

Assessment of the Prediction Power of Forced Ageing Methodology on Lager Beer Aldehyde Evolution during Maritime Transportation.

The globalisation of the beer market forces brewers to have methodologies that rapidly evaluate the evolution of beer flavour stability. Commonly used forced ageing methods have limitations since temperature and transportation conditions (temperature, vibrations, long-distance travel, and other factors) impact beer quality. This study assessed the prediction power of a forced ageing methodology on the evolution of aldehydes during maritime transportation across four sample groups (maritime transport, storage simulation, and three ageing periods: 7, 21, and 28 days at 37 °C), which differed in their bottle-opening system (either crown cap or ring pull cap). The results revealed that forced ageing up to 28 days could estimate the evolution of phenylacetaldehyde, 3-methylbutanal, 2-methylpropanal, and hexanal during maritime transport. In contrast, the benzaldehyde content was consistently underestimated, on average, 0.8 times lower. In general, the ageing conditions significantly favoured the formation or liberation from a bound state, up to 2.2 times higher, of trans-2-nonenal, acetaldehyde, and 5-hydroximethylfurfural in comparison to the levels registered on exportation simulation beers. Moreover, forced-aged beers with ring pull caps developed quantifiable levels of nonanal and increased phenylacetaldehyde, benzaldehyde, and acetaldehyde content over time. Moreover, thermal stress induced a continuous increase in the extent of beer staling, up to seven times higher, in most samples.

A Look at Three Key Malt Derived Mechanisms of Beer Staling and Practices of Mitigation​

A Look at Three Key Malt Derived Mechanisms of Beer Staling and Practices of Mitigation​

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.

On the contribution of malt quality and the malting process to the formation of beer staling aldehydes: a review

Despite decades of extensive research, beer flavour instability remains a challenge for both brewing and malting industries. Malt impacts the brewing process as well as the quality of the final beer. It also affects the stability of beer flavour, as it delivers to the brewing process various compounds with the potential to compromise the desired flavour characteristics of beer. These include staling aldehydes and their precursors, such as amino acids, reducing sugars, α-dicarbonyls and bound-state aldehydes. In general, the content of these compounds depends on barley variety and quality, the malting regime and final malt quality. Malt that represents a low potential for beer staling, i.e. that has low values of Kolbach Index, heat load, colour, LOX activity, Strecker aldehydes, transition metal ions and high antioxidative activity, leads to beer with enhanced flavour stability. However, the consistent production of malt with the desired quality remains challenging. Approaches to achieve this include adjustment of steeping and germination conditions, allowing control of grain modification and thus, the reservoir of aldehydes precursors. Also, the application of alternative kilning technologies may reduce the applied heat load, responsible for the formation of staling aldehydes and triggering development of the oxidising free radical species. This review provides an evaluation of current knowledge on the contribution of the malting process and malt quality to the formation of beer staling aldehydes. © 2021 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling.

Determination of optimal sample preparation for aldehyde extraction from pale malts and their quantification via headspace solid-phase microextraction followed by gas chromatography and mass spectrometry

Aldehydes originating from malt play an important role in beer flavour deterioration. In order to better understand the influence of malting process on beer staling, it is necessary to acquire a reliable analytical methodology for determination of beer staling aldehydes in malt. Therefore, the aim of this study was to evaluate extraction parameters, which allow quantification of beer staling aldehydes present in pale malts. The method was validated with respect to linearity (R > 0.9988), limit of detection (0.28 – 0.99 μg/L), limit of quantification (0.92 – 3.31 μg/L), accuracy (± 5%), repeatability (1.3 – 5.3%) and intermediate precision (>20%). The following parameters of sample preparation were evaluated: sample amount, extraction time and temperature, ultrasonication time and oxygen level. Consequently, the best extraction conditions were successfully applied on pale malts. After extraction, the samples were analysed by headspace solid-phase microextraction (HS-SPME) with on fibre carbonyl derivatisation followed by gas chromatography and mass spectrometry (GC–MS). In addition, the salting-out effect during HS-SPME was studied. The method application allowed to identify significant differences (p ≤ 0.05) in the levels of aldehydes among various industrial scale, pale malts. The optimised method could give the information on the aldehyde content introduced into the brewing process and its potential contribution to the overall beer quality.

Determination of free fatty acids in beer

Free fatty acids (FFA) content of beer affects the ability to form a stable head of foam and plays an important role in beer staling. Moreover, the presence of saturated FAs is related sometimes to gushing problems in beer. The aim of this research was to validate an analytical method for the determination of FFAs in beer. The extraction of FFAs in beer was achieved via Liquid–Liquid Cartridge Extraction (LLCE), the FFAs extract was purified by Solid Phase Extraction (SPE), methylated by boron trifluoride in methanol, and injected into GC-FID system. The performance criteria demonstrate that this method is suitable for the analysis of medium and long chain FFAs in beer. The proposed method was tested on four experimental beers.

Manganese in Brewing Raw Materials, Disposition during the Brewing Process, and Impact on the Flavor Instability of Beer

Like iron and copper, manganese promotes the staling of beer, by converting ground state oxygen to reactive oxygen species. Manganese was detected in beers at levels that are likely to impact the aging of beer. Manganese originates in the grist materials but is present at even higher levels in hops. Although there is substantially more iron in those hops than manganese, the delivery into beer of these ions is much greater for manganese. Leaching of manganese into beer is much higher than in the equivalent quantity of deionized water. This study suggests that further study is warranted into the adverse impact of dry hopping on the flavor stability of beers.

Exploring the Binding Behavior of Beer Staling Aldehydes in Model Systems

Increases in the levels of staling aldehydes during beer aging are likely to involve bound aldehydes, already present in fresh beer. In particular, bisulfite adducts and imines have been reported as bound-state aldehyde forms and thus potential sources of off-flavor aldehydes. In this study, using headspace solid-phase microextraction followed by gas chromatography-mass spectrometry, a new type of bound-state aldehyde is proposed, namely 2-substituted 1,3-thiazolidine-4-carboxylic acids, resulting from the reaction between the amino acid cysteine and an aldehyde. The binding behavior of aldehydes toward cysteine appears to be similar to their binding behavior toward bisulfite and can be linked to the electrophilicity of the carbon atom of the carbonyl group of the particular aldehyde. Remarkably, within a pH range of 4.4 to 6.0, relevant to malting and brewing, the pH of the reaction mixture was shown to affect the binding of (E)-2-nonenal to both bisulfite and cysteine (more binding at higher pH) but not the binding of its saturated counterpart, i.e., nonanal. Finally, within the experimental setup employed, imine formation resulting from interaction between amino acids and aldehydes was not confirmed.

Determination of free fatty acids in beer wort

The importance of free fatty acids (FFAs) in wort has been known for a long time because of their influence on beer quality and yeast metabolism. Lipids have a beneficial effect on yeast growth during fermentation as well as negative effects on beer quality. Lipids content of beer affects the ability to form a stable head of foam and plays an important role in beer staling. Moreover, the ratio of unsaturated and saturated fatty acids seems to be related to gushing problems. A novel, simple, and reliable procedure for quantitative analysis of FFAs in wort was developed and validated. The determination of FFAs in wort was achieved via liquid–liquid cartridge extraction, purification of FFA fraction by solid phase extraction, boron trifluoride in methanol methylation, and injection into GC-FID system. The proposed method has high accuracy (<0.3%, expressed as the bias), high precision (<1.2%, RSD), and recoveries ranging from 74% to 98%. The method was tested on two different wort samples (9° and 12° Plato).

Influence of barley variety and malting process on lipid content of malt

The lipid content of a beer affects its ability to form a stable head of foam and plays an important role in beer staling. The concentration and the quality of lipids in beer depend on their composition in the raw materials and on the brewing process and they may exert considerable influence on beer quality. This paper presents an investigation of the influence of barley variety and malting process on the lipid content of finished malt. Five barley samples, grown in Italy, representing 4 spring barley and 1 winter barley were used. The samples were micro-malted and analysed. The aim of this research was to verify the influence of different barley varieties on the lipid content of malt and also on the changes in fatty acid (FA) profile during the malting process. Lipid content and FA profile were evaluated. Principal component analysis (PCA) was used to establish relationships between the different samples. An evaluation of the correlation between lipid content of barleys and the quality of the resulting malts was also conducted. The data showed that the total lipid content during the malting process decreased significantly as barley was converted into malt. Different barley varieties present different FA contents and different FA patterns. The correlation between the lipid content of barley and the quality of the resulting malt confirmed the negative influence of lipids.

Use of optical oxygen sensors to monitor residual oxygen in pre- and post-pasteurised bottled beer and its effect on sensory attributes and product acceptability during simulated commercial storage

Disposable optical oxygen sensors were used to non-destructively assess the levels of residual oxygen in the headspace of commercially produced Lager beer in 330 ml clear glass bottles. Monitored before and after pasteurisation, oxygen concentration was observed to drop as oxygen diffused into the beer. Oxygen levels between 0% and 5% were present in the bottle headspace pre-pasteurisation. Oxygen diffusion into the beer was monitored over time under refrigeration (∼4 °C) and a sensory panel was used to determine the effect of residual oxygen on the sensory quality of the beer. The headspace in the bottles was also monitored over time where oxygen increased to a level of ∼0.5% on average over the course of the shelf life. Interestingly, results showed that beer samples possessing higher levels of oxygen present prior to pasteurisation also possessed the most negative sensory attributes associated with the beer, particularly those consistent with beer staling. The developed optical sensor was shown to act as a predictor of sensory quality and may have on-line applications in the beer packaging sector.

Analytical and sensory assessment of hoppy aroma and bitterness of conventionally hopped and advanced hopped Pilsner beers

Analytical and sensory aspects of hoppy aroma of conventionally hopped and advanced hopped pilot Pilsner beers were investigated. Linalool and several sesquiterpenoids were used as analytical markers for the hoppy aroma of the beers. Levels of linalool and sesquiterpenoids in the fresh beers, as well as sensory characteristics of hoppy aroma (intensity and attributed aroma descriptor(s)) clearly depended on the applied hop aromatisation technology and on the type of hop oil fraction used in advanced hopping. The most pronounced hoppy aroma was observed for the advanced bittered beers, either aromatised post-fermentation using a polar hop essence or at the end of wort boiling using pellets (late-hopping). However, all refined hop oil fractions used in this study for advanced aromatisation clearly affected the hoppy aroma impression. Analytical data on staling indicators, combined with sensory evaluations, further suggest that hop oil preparations may also affect flavour stability of the resulting beers in a positive way. In general, it can be concluded that hop aromatisation, whether performed in the advanced or conventional way, appears to mask beer staling, as demonstrated by lower overall sensory ageing scores.

The Influence of Hopping on Formation of Carbonyl Compounds During Storage of Beer

Improving beer flavour stability is an important brewing goal. Pilot scale brewing trials (50 L) were performed that focused on the determination of the influence of hop pellet dosage and dosage timing on carbonyl compounds in stored beer. The reducing activity of experimental worts, beers and stored beers appeared to depend on the hop pellet dose. Brews with lower amounts of hop antioxidants showed an enhanced formation of carbonyl compounds over the course of beer storage. A correlation between DPPH reducing activity and the content of some carbonyls, including the important markers 2-furfural and (E)-2-nonenal, was found. Fresh and aged beers hopped by different amounts of hop pellet doses were clearly distinguishable according to their carbonyl content using Cluster analysis. Results of the sensorial analysis corresponded to the analytical criteria values. Results of this study bring further evidence of the indispensable impact of hop antioxidants on the suppression of undesirable carbonyl compound formation in the course of beer staling, which can be significant in beers hopped by aroma hops. However, hop antioxidants are only one of many factors affecting beer staling.

The Peroxide Challenge Test: A Novel Method for Holistic Near-Real Time Measurement of Beer Flavour Stability

A holistic approach is paramount to reliably measure beer staling. As a consequence, the peroxide challenge test (PCT) was developed as an alternative to electron spin resonance (ESR). The principle of the PCT is to mimic oxidation by titrating beer with hydrogen peroxide. The more hydrogen peroxide a beer can quench, the more resistant it is against oxidation and flavour deterioration. The PCT allows cost effective, near real time, high throughput assessment of beer flavour stability. The PCT is convenient and inexpensive to perform and the results correlate with ESR measurements and the perceived aged character of beer.

(E)-2-Nonenal determination in brazilian beers using headspace solid-phase microextraction and gas chromatographic coupled mass spectrometry (HS-SPME-GC-MS)

(E)-2-nonenal is considered an important off-flavor of beer, related to the flavor of beer staling. In this study, a new method for determination of (E)-2-nonenal in beer using headspace solid-phase microextraction and gas chromatographic coupled mass spectrometry (HS-SPME-GC-MS) was developed and applied in Brazilian beer samples. The extractions were carried out in CAR-PDMS (carboxen-polydimethylsiloxane) fiber and the best results were found with 15 minutes of equilibrium and 90 minutes of extraction at 50 °C. The method was linear in the range from 0.02 to 4.0 μg.L-1 with correlation coefficient of 0.9994. The limits of detection and quantification were 0.01 and 0.02 μg.L-1, respectively. 96.5% of recovery and 4% precision (RSD) were obtained in the fortification of beer samples with 2.0 μg.L-1 of (E)-2-nonenal. The developed method proved to be simple, efficient and highly sensitive to the determination of this analyte being easily applied in the quality control of the brewery. (E)-2-nonenal was found in all beer samples analyzed with levels between 0.17 and 0.42 μg.L-1.

Analytical and Sensory Assessment of Hoppy Aroma and Bitterness of Conventionally Hopped and Advanced Hopped Pilsner Beers

Analytical and sensory aspects of hoppy aroma of conventionally hopped and advanced hopped pilot Pilsner beers were investigated. Linalool and several sesquiterpenoids were used as analytical markers for the hoppy aroma of the beers. Levels of linalool and sesquiterpenoids in the fresh beers, as well as sensory characteristics of hoppy aroma (intensity and attributed aroma descriptor(s)) clearly depended on the applied hop aromatisation technology and on the type of hop oil fraction used in advanced hopping. The most pronounced hoppy aroma was observed for the advanced bittered beers, either aromatised post-fermentation using a polar hop essence or at the end of wort boiling using pellets (late-hopping). However, all refined hop oil fractions used in this study for advanced aromatisation clearly affected the hoppy aroma impression. Analytical data on staling indicators, combined with sensory evaluations, further suggest that hop oil preparations may also affect flavour stability of the resulting beers in a positive way. In general, it can be concluded that hop aromatisation, whether performed in the advanced or conventional way, appears to mask beer staling, as demonstrated by lower overall sensory ageing scores.

Structure, Organoleptic Properties, Quantification Methods, and Stability of Phenolic Compounds in Beer—A Review

Beer composition changes through storage, altering the quality of the product. In the past decade, many papers have been devoted to the compounds responsible for aged-beer off-flavors, mainly trans-2-nonenal, methional, and dimethyltrisulfide. Due to their huge antioxidant activity, polyphenols have often been described as key compounds for limiting beer staling. Yet phenolic structures also evolve through storage. Low-molecular-weight phenols like 4-vinylsyringol can impart off-flavors in aged beer, whilst flavonoids strongly influence astringency, haze, and color. The instability of stilbenes, prenylchalcones, and derived flavanones could also modify their health potential through storage. After reviewing the structures and properties of all phenolic compounds found in beer, this paper will try to assess the impact of their degradation through aging. Extraction procedures for their quantification and treatments for their removal are also described.

Technological Steps and Yeast Biomass as Factors Affecting the Lipid Content of Beer during the Brewing Process

Knowledge of lipid content and composition in the brewing process enables the quality control of the final product. Lipids have a beneficial effect on yeast growth during fermentation as well as deleterious effects on end-product quality. The lipid content of a beer affects its ability to form a stable head of foam and plays an important role in beer staling. Lipid oxidation during wort production is of great interest because of its effect on beer quality: both lipids and their oxidation products are known to have adverse effects on beer flavor, whereas interactions between lipids and protein films stabilizing the gas bubbles are thought to cause the collapse of foam. In this background, the aim of this research was the characterization of the lipid content during a brewing process for evaluating the influence of both technological steps and yeast biomass in the lipid composition of beer. Lipid contents and their fatty acid profile were evaluated in brewing raw materials, wort, and beer. A high-resolution gas chromatography-flame ionization detector (HRGC-FID) system was used for fatty acid determination in lipid extracts. The results of the present study highlighted that the main technological steps influencing the lipid content in brewing byproduct and beer were clarification in a whirlpool and filtration. Moreover, the presence of metabolically active yeast cells (used as starter culture) were found to have a great influence on the fatty acids composition of lipids.