Hopped Beers Research Articles

Impact of Pasteurisation on Terpenes, Terpenoids, Aldehydes and Esters in Hoppy Ales on Ageing

Pasteurisation is a common technique to achieve microbial stability of beer. In dry hopped beer, pasteurisation is the ultimate measure to assure product quality and consumer safety. To gain insights into the effects of pasteurisation on the chemistry of hoppy ales the time related changes of aldehydes, terpenes, terpenoids and esters in an unpasteurised and pasteurised session India Pale Ale (SIPA), two IPAs, and a double IPA (DIPA) were monitored. The ales were stored at 4 °C and 20 °C for 52 wk to evaluate chemical differences between the two treatments. It was found that pasteurisation led to an immediate increase of staling aldehydes (i.e., furfural and 2-methylpropanal), a decrease of fermentation esters (e.g. ethyl octanoate) and hop related esters (e.g. 2-methylbutyl isobutyrate) in fresh beer, while terpenes and terpenoids were hardly affected. When the beers were stored, unpasteurised ales were chemically less stable compared to the pasteurised ones. Differences between pasteurised and unpasteurised ales were dependent on storage temperature. The results of this study highlight that pasteurisation is favourable when aiming to achieve an increased shelf life of up to 12 months, as the negative influence of the heat impact is compensated after 1 month of storage at ambient (20 °C) temperature.

A hypothesis-based hop microbiology laboratory module testing the plausibility of the mythical origin of the India Pale Ale.

As one of the most famous fermented drinks in the world, beer is an especially relatable topic for microbiology courses. Here, we describe a short and easily adaptable module based on the antibacterial properties of hops used in brewing. By the 15th century, beer recipes included hops (the flower of the Humulus lupulus plant) as a bittering agent and antimicrobial. By the 19th century, the highly hopped Indian Pale Ale (IPA) became popular, and a modern myth has emerged that IPAs were invented to survive long ocean voyages such as from Britain to India. With that myth in mind, we designed a hypothesis-driven microbiology lab module that tests the plausibility of this brewing myth-namely that highly hopped beers possess enough antibacterial activity to prevent spoilage, while lowly hopped beers do not. The overall design of the module is to test the antimicrobial properties of hops using petri plates containing varying concentrations of hop extract. The module includes hypothesis generation and testing related to bacterial physiology and cell envelope morphology (hops are not equally effective against Gram-positive and Gram-negative bacteria) and to mechanisms of antimicrobial resistance (as beer spoilage bacteria have repeatedly evolved hop resistance). Pre- and post-assessment showed that students made significant gains in the learning objectives for the module, which encourages critical thinking and hypothesis testing by linking microbial physiology and antimicrobial resistance to an important and topical real-world application.

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.

STUDY OF THE INFLUENCE OF A HIGHER HOPPING DEGREE OF WORT ON THE FUNCTIONAL PROPERTIES OF ALE BEER

Experiments have been conducted to determine the effect of a higher hopping degree of wort (120 mg/l and 200 mg/l bitter α-acids) on the antioxidant capacity of ale beer. In one of the experimental variants, dry hopping with aromatic hop pellets (3 g/l) was applied. The higher hopping degree of wort did not lead to disturbance in the fermentation process. For beers containing 200 mg/l α-acids, the most significant was the increase in flavonoids (20.6-23.8%) compared to the variant with 120 mg/l α-acids. The polyphenols in highly hopped beer were increased by 6.6-7.1% compared to moderately hopped beer. The content of anthocyanins was not significantly affected by the addition of more hops. Antioxidant activity, expressed as equivalent vitamin C mmol/l, showed an increase of 4-5.2% for highly hopped beers compared to the control variant; when calculated relative to vitamin E, the increase was 5.8-7.5%. All beers were light, with excellent clarity and enhanced hop aroma.

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.

Study on the Composition of Hop Terpenes and Terpenoids by Steam Distillation and Effects on Beer Flavor by an Ale Yeast

Model systems of adding three distillates (hop oil, water-soluble aqueous, and residual aqueous) in model wort (buffer) and wort were used to produce model beers and special beers, respectively (with an ale yeast and fermentation at 18 °C). The attributes of hoppy flavor and organoleptic quality were comprised of sustained, surged, generated, or diminished oxygenated compounds and hydrocarbons by yeast biosynthesis in hop essential oil and non-volatile precursors. The matrix of content and instrumental composition of oxygenated terpenoids and hydrocarbons (terpenes and sesquiterpenes) and sensorial profile of model systems was directionally correlated to the matrix and sensory of the early hopped, late hopped, and dry hopped beers. The occurrence of hop aroma profile of the residual aqueous is reminiscent to traditional early kettle hopped beer. The water-soluble volatile components added beer were remarkably close to the distinctive odor profile of late hopped beer. However, dry hopped beer was seemingly a coupling of the hop oil and the water soluble aqueous added beers, but its perception was closer to the latter. The mechanism of the growth of nerol, citronellol, and methyl geranate via a reversed biosynthesis of free linalool by ale yeast and fermentation at 18 °C is contrary to a pathway via geraniol from the hop oil or the water-soluble aqueous. Free linalool was sustained after yeast hydrolysis of linalyl glycoside and related to metabolites in the residual aqueous due to sluggish yeast activity in the model wort (buffer) but not in the wort.

Pilot brewery tests of Czech flavour hop varieties registered in 2022

Seven new Czech “flavour hop” varieties were tested in pilot brewing trials (50 l), in which samples of Ale-style beer were prepared using dry hopping. Essential oils in the beer were determined by fluidized-bed extraction combined with gas chromatography–mass spectrometry. Hop-derived aromas in beer were evaluated by descriptive method. Comparison of terpene essential oils in samples showed differences between hop genotypes and only a partial relationship with the sensory profile of beer. A cluster analysis of hop aromas in beer revealed the relationship between the pairs of Saturn and Pluto; N and Eris; Ceres and Jupiter hop varieties. The submitted results present the sensory properties of these new varieties and are useful for further study of the relationship between chemical and sensory profile of dry hopped beers.

A Search for Diastatic Enzymes Endogenous to Humulus lupulus and Produced by Microbes Associated with Pellet Hops Driving “Hop Creep” of Dry Hopped Beer

A search was conducted for the sources of diastatic enzymes driving the over attenuation and continued fermentation of dry hopped beer known as “hop creep”. Microbial cultivation using starch containing media and assays of amylase enzyme activity were used to isolate and identify microbes from pellet hops that are potential sources of amylases associated with but exogenous to hops (Humulus lupulus). Bacteria and fungi associated with pellet hops produced amylases but did not produce hop creep in assays using finished beer and fermenting wort with added microbes. Cannabis sativa flower produced over attenuation of fermenting wort equivalent to that seen with hops. Comparative bioinformatic analysis of the Cannabis sativa proteome and H. lupulus genome revealed the genetic potential of H. lupulus to produce endogenous amylase enzymes. Sequence similarity of amylases annotated in the C. sativa proteome to previously unidentified genes in H. lupulus revealed 13 genes likely encoding amylases. PCR and sequencing confirmed the occurrence of genes that appear to encode α-amylase and β-amylase in the Citra® hop cultivar. Identifying a genetic basis for hop creep contributes knowledge that may lead to new approaches for controlling hop creep produced by endogenous amylases of H. lupulus.

The Influence of Hop Phenolic Compounds on Dry Hopping Beer Quality.

Background: The article considers the phenolic hop compounds’ effect on the quality indicators of finished beer. The topic under consideration is relevant since it touches on the beer matrix colloidal stability when compounds with potential destabilizing activity are introduced into it from the outside. Methods: The industrial beer samples’ quality was assessed by industry-accepted methods and using instrumental analysis methods (high-performance liquid chromatography methods—HPLC). The obtained statistical data were processed by the Statistics program (Microsoft Corporation, Redmond, WA, USA, 2006). Results: The study made it possible to make assumptions about the functional dependence of the iso-α-bitter resins and isoxanthohumol content in beer samples. Mathematical analysis indicate interactions between protein molecules and different malted grain and hop compounds are involved in beer structure, in contrast to dry hopped beer, where iso-a-bitter resins, protein, and coloring compounds were significant, with a lower coefficient of determination. The main role of rutin in the descriptor hop bitterness has been established in kettle beer hopping technology, and catechin in dry beer hopping technology, respectively. The important role of soluble nitrogen and β-glucan dextrins in the perception of sensory descriptors of various technologies’ beers, as well as phenolic compounds in relation to the formation of bitterness and astringency of beer of classical technology and cold hopping, has been shown. Conclusions: The obtained mathematical relationships allow predicting the resulting beer quality and also make it possible to create the desired flavor profiles.

Advances in dry hopping for industrial brewing: a review

highly hopped and dry hopped beer production and consumption has increased steadily for the last twenty years, following the rise of craft breweries in the United States of America and the trend they set over the world. This overuse of hops offers some environmental, technological, and economic challenges for the beer industry. Researchers have been studying several ways to make beer more ecofriendly by promoting reuse of spent hops and increasing extraction yields. Dry hopping is a size-dependent process, making it feasible for craft breweries with their small scale production, but quite a challenge for larger tanks and breweries. Based on the literature and industrial experience from brewers, the aim of this research was to analyze and discuss different dry hopping methodologies for the brewing industry and how the parameters affect the final product. In order to shed light on this trending topic and to better aid brewers in choosing the most suitable, efficient, and environmental-friendly dry hopping process for their brewery, this work approaches the main variables that promote aroma transfer from hops into beer and how to optimize it.

Finding correlations between hop catalogs and real hoppy character in brewery conditions

Brewing recipe design is mainly based on brewer’s expertise, information available in catalogs and certificates of analysis (CoA’s). Hop schedule design and formulation has become an essential topic since hoppy craft beers took the scene. But how accurate is the flavor profile information provided in catalogs? How useful is the chemical composition profile information in CoA’s? Besides current research and tons of reported experiences, hops impact is still a mystery, and topics like biotransformation are black-boxes for brewers. In this study, nine single hopped beers were brewed, and a trained panel conducted sensorial beer analysis. Then, to asses hop impact, qualitative and process-related-quantitative beer characteristics were contrasted to find valuable correlations and trends between hop catalogs and final beers. Discrepancies with catalog qualitative data were reported. In addition to what is already described in the literature, here we describe how α-acids, linalool, myrcene, and geraniol (despite the classical use for these compounds) could predict positive and negative hop impact of nine different hop varieties on bitterness, flavor, and aroma, when they are applied in different brewing process steps. Also, with this pipeline we stand the basis of a tool to be improved, available for brewers, to better predict their brews and assess new hop varieties in real-life pilot brewing set ups.

Brewing tests of new fine aroma hop varieties (Humulus lupulus L.) Saaz Brilliant, Saaz Comfort and Saaz Shine

Characterization of varietal profiles of hop secondary metabolites in beer is of considerable importance for hop growing and brewing. This three-year study focused on pilot brewing tests of three new Saaz derived hop varieties, namely Saaz Brilliant, Saaz Shine and Saaz Comfort. The sensory profiles of kettle and kettle+dry single hopped beers were monitored. At the same time, the impact of dry hopping technology on sensory perception of final beers and changes in volatile compounds was investigated. Pilot brews (200 l) of 12% pale lager were prepared in kettle and kettle+dry variants using the new Czech varieties and traditional Saaz as a control sample. Essential oils in beers were determined by GC/MS-MS method with the aim to clarify links to the beer sensory profile of both, kettle and dry hopping mode. The descriptive sensory method of hop-derived aromas and the triangle tests were employed to determine the sensory quality of beer. The overall sensory impression of beers from all tested varieties was at least comparable to traditional Saaz, and Saaz Comfort even reached better evaluation. The profile of essential oils and hop flavours in beer was partially different, however it was not rated worse than Saaz. The kettle+dry hopped beers of new varieties were significantly different from Saaz in the triangle test, Saaz Brilliant was preferred over the Saaz. The results showed considerable potential of new varieties for the production of interesting and taste-specific beers and the enrichment of the spectrum of fine aroma varieties of Czech hops.

Properties of Dry Hopped Dark Beers with High Xanthohumol Content.

The antioxidant activity of beers comes mainly from phenolic compounds and melanoidins. The aim of this research was to evaluate the effect of technological operations, especially the ethanol fermentation process using top fermentation brewer’s yeast Saccharomyces cerevisiae, on the antioxidant activity of dark dry hopped beers with a high xanthohumol content. Four beers were produced using different varieties of hops. The polyphenol content during beer processing increased at the stage of hopping and fermentation, while it decreased during aging. The ability to reduce iron ions increased for all beers compared to hopped wort. The opposite tendency was noted for the antioxidant capacity expressed as the ability to reduce the radical cation ABTS•+ generated from 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid). Fermentation and aging caused a decrease in beer color intensity. The content of 5-hydroxymethylfurfural (5-HMF) increased with the color intensity of wort, therefore in beers no presence of 5-HMF was observed. The beers were characterized by a distinctly high content of xanthohumol in the range of 1.77–3.83 mg/L and 0.85–1.19 mg/L of isoxanthohumol. The content of prenylflavonoids and bitterness of beer depended on the variety of hops used.

Saaz Special – another hop variety recommended for Czech beer

The specification of varietal profiles of secondary metabolites of hops in beer is rather important for hop growing and beer brewing. Chemical and sensory profiles of beers hopped with the varieties of Saaz Special and the traditional Saaz semiearly red bine hops (Saaz) were compared in three-year pilot brews (200 L). Single kettle hopped beers and single kettle + dry hopped beers were prepared. The overall sensory impression of the Saaz Special beers was comparable to Saaz hops. The profile of essential oils and hop aromas/flavours in the beer was partially different, but the hop aroma did not receive a worse rating than Saaz. The Saaz Special dry hopped beers were clearly distinguished from Saaz in triangle tests, but no preference was given to either variety. Based on the achieved results, the Saaz Special variety was listed among varieties recommended for the production of the beer with the Protected Geographical Indication of Czech Beer thanks to the achieved results.

A comparison of sensory evaluation and an electronic nose assay in the assessment of aroma in dry hopped beers

The aim of this work was to compare sensory evaluation and electronic nose technology used to assess aromas in dry hopped beers. An electronic nose based on gas chromatography was used for the first time. Hops varieties Amarillo, Cascade, Chinook, Kazbek and Mandarina Bavaria were used for the production of dry hopped beers and the Sladek variety was used for the control sample. The basic characteristics of the beers were determined, and the sensory evaluation performed by selected assessors was compared to the sensory assay using an electronic nose. Assessment of the aroma profile of dry hopped beers shows that the basic flavours of these beers, such as worty, yeasty and hoppy, were suppressed. Compared to the control sample, a significant grapefruit flavour was noted by the evaluators in Kazbek and Chinook beer samples. The most prominent determinant, compared to the control sample, was in general the citrus aroma. Based on the results of the principal component analysis, it can be concluded that there were statistically significant differences between the individual dry hopped beers and between them and the control sample with the exception of beers dry hopped with hops of the Amarillo and Cascade variety, which was also confirmed by the results of sensory evaluation (approximately the same scoring of the monitored descriptors).

Headspace‐solid phase microextraction and GC‐MS followed by multivariate data analysis to study the effect of hop processing type and dry hopping time on the aromatic profile of top‐fermented beers

AbstractThis study analyzes the impact of the pelletizing process and the contact time of hops with beer samples on the aroma of beers produced with a dry hopping technique. Eight different hopped beer samples were produced, varying in terms of hop variety (Cascade or Columbus), two different commercial forms of hops (pellets or whole flowers) and two dry hopping times (4 or 7 days). A non‐hopped beer was also produced to help understanding which compounds emerge from the dry‐hopping technique alone. The volatile fraction of the beers was studied by headspace‐solid phase microextraction and gas chromatography‐mass spectrometry. More than 90 compounds were identified with the help of Kòvats retention index, injection of standards, and comparison with mass spectra of the NIST library. To assist in the interpretation of the large data volume, principal component analysis was used. The findings confirm that the pelletizing process and the dry hopping time influence to different extents the aromatic profile of the beers produced, and the compounds responsible for these changes were identified.

Kazbek – The First Czech Aroma “Flavor Hops” Variety: Characteristics and Utilization

The world market of craft beer, especially dry hopped beers, has been constantly growing in the last few years. That is why new varieties of hops are still being bred. This article gives the genetic, agronomic, chemotaxonomic and brewing characteristics of Kazbek, the first “flavor hops” variety bred in the Czech Republic. Kazbek genetically belongs to a group of bitter American hops resulting from Brewers Gold variety, but the alpha acids content is relatively low, 5.0–8.0% by weight. The content of a homologous series of geranyl esters (acetate – propionate – isobutyrate) in an amount 2–4% of total essential oils (1–1.5 g/100g) is considered to be the originator of the specific, mainly citrus-like aroma of Kazbek. Moreover, the essential oil fraction contains about 25 sulfurous substances, predominantly thioesters. In the pilot scale brewing tests, the quality of Kazbek hops was proved both in kettle and dry hopping of Pilsner lagers. The overall sensory impression of kettle hopped lagers was comparable to Saaz hops, the differences were in the character of hop-derived flavor and bitterness. The best results of dry hopped beers were achieved for a 2.5 g/l hop dose and a contact time of 3 days.

Hop aroma characterization of dry hopped beers using Headspace-Trap GC-MS

In the brewing process hop is a major ingredient which provides a distinctive aroma and characteristic bitter taste. The breeding of new hop cultivars with a multitude of aromas and the increasing popularity of dry hopped beers called for detailed insights into beer aroma influenced by hop. Headspace sampling is a suitable technique for extraction of aroma compounds from complex matrices. The benefit of the use of a trap device in combination with headspace is the improvement of detection limits. In this study, a headspace (HS)-trap gas chromatography (GC)-mass spectrometry (MS) method was developed to study dry hopping aroma in beer. Analysis of monoterpenes, sesquiterpenes, terpene alcohols, esters, and ketones in various beer samples was performed. The influence of different hop cultivars (‘Mandarina Bavaria’, ‘Lemondrop’, ‘Bravo’, ‘Hallertau Cascade’, ‘Polaris’, ‘Smaragd’, ‘Saphir’, ‘Calypso’, and ‘Hallertau Blanc’) on the aroma profile of beer as well as the impact of hop addition time for the hop cultivar ‘Lemondrop’ was investigated. The HS-trap GC-MS technique covers a broad range of hop-derived aroma compounds and enables to monitor the volatiles during the whole brewing process.

Tajemství výroby studeně chmelených piv - přehled

Tajemství výroby studeně chmelených piv - přehled

Investigations on the Impact of the Special Flavor Hop Variety Huell Melon on the Odor-Active Compounds in Late Hopped and Dry Hopped Beers.

Bottom-fermented and top-fermented beers, both either late or dry hopped with Huell Melon hops, and respective reference beers without late or dry hopping were subjected to a comparative odorant screening by aroma extract dilution analyses. On the basis of differences in the FD factors, 14 odorants were identified as hop-derived. Among them were ethyl 2-methylpropanoate, methyl 2-methylbutanoate, ethyl 2-methylbutanoate, propyl 2-methylbutanoate, myrcene, linalool, and geraniol. Differences between late hopped, dry hopped, and reference beers were substantiated by quantitation. Results showed minimal transfer of myrcene from hops into beer. Moderate transfer was observed for propyl 2-methylbutanoate, geraniol, and linalool. Process-induced changes of ethyl 2-methylpropanoate, ethyl 2-methylbutanoate, and methyl 2-methylbutanoate were beyond a direct transfer from hops into beer, suggesting a formation from the corresponding hop-derived carboxylic acids by yeast. Spiking experiments revealed that linalool and propyl 2-methylbutanoate contributed particularly to the characteristic aroma of beers flavored with Huell Melon hops.