Dry Hopped Beers Research Articles

Chemical and sensory profile of lager beers hopped with new Czech bitter varieties Boomerang and Gaia

Characterising the sensory profiles of beers made from new hop varieties is of considerable importance for their application in brewing. New Czech bitter varieties Boomerang and Gaia were tested in three-year pilot brews (200 l) of 12% single-hopped pale lager, produced in kettle and kettle+dry-hopped variants. The hop-derived aroma and bitterness profile of the beers was evaluated using a comprehensive descriptive method. Hop-related volatiles in beer were determined by GC/MS-MS method. Both of these bitter varieties showed a pleasant bitterness profile even in dry-hopped beers. The overall impression of the beers from the varieties tested was favourable, at the level of the control beer (Saaz). The profile of hop derived volatiles and aroma in beers from Gaia and Boomerang varieties were different. The results show the potential of Boomerang for both single kettle-hopped beers and dry-hopped lagers due to its interesting aroma profile (spicy, herbal, floral). The Gaia variety can be used in a similar way, with a preference for dry hopping to give a well-balanced hop-derived aroma profile. Both varieties have shown considerable potential for the production of new beer brands, and their drought tolerance may also help their widespread cultivation.

Comparison of phytochemical and brewing characteristics of Cascade and Kazbek hop cultivars

A four-year study compared the secondary metabolite profile of two flavour hops, the widely used Cascade and the new Czech variety Kazbek. The average alpha-acids and total essential oil of Kazbek and Cascade grown in Europe did not differ, while alpha-acids were 20 % higher in Cascade grown in the USA. Cluster analysis of essential oil composition distinguished the varieties, the markers being mainly farnesene derivatives. US-Cascade had higher terpenoids (geraniol, geranial) and lower fatty acid methyl esters than EU-Cascade. Both varieties have high and comparable levels of geraniol esters (230–360 mg/kg total) and low levels of free geraniol. The sulphur-containing volatile profile of US-Cascade and EU-Cascade hops differed significantly, probably as a result of treatment with different pesticides. The profile of hop-associated essential oils and aroma components of the single-variety experimental beers Kazbek and Cascade was similar for both whirlpool-hopped and additionally dry-hopped beers. Citrus and fruit notes were the dominant descriptors. Two independent sensory panels did not clearly distinguish or prefer beers hopped with Cascade and Kazbek hops, demonstrating the possibility of alternating between the two varieties in brewing. A new finding is that genetically distant hop varieties can provide similar sensory profiles in late- and dry-hopped beers.

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.

Characterization of Brazilian Cascade and Chinook hops and their dry-hopped beer

The flowers (cones) of Hop (Humulus lupulus L.) have extensive applications in the brewery industry and in Brazil, 98% of which is imported. The Brazilian cultivated hops have multiple flowerings, and therefore the cone cultivation period could be shortened. Herein, Cascade and Chinook whole cones cultivated in Brazil were analyzed and compared with American pellets. Following the European Brewery Convention (EBC) methodology, the contents of alpha acids, polyphenols, and essential oils were quantified and used as comparison criteria. Amidst the Brazilian Cascade essential oils, isoamyl propanoate and 6-methyl heptanoate were identified, both of which were responsible for pineapple aromas and were absent in American pellets. The dry hopping (DH) process promoted higher alcohol beverage value, lower dissolved oxygen, and higher polyphenol values. In comparison with the commercial counterpart, the Brazilian Cascade hops presented similar characteristics, but with different organoleptic properties (terroir), inherent to their growing place. The resulting terroir adds value to the Brazilian Cascade usage, considering the DH overall process and the application in special beers.

Identification of the Yeast Mannoprotein Gene HZY1 as a Key Genetic Determinant for Yeast-Derived Haze in Beer

With the sustained popularity of hazy IPAs, brewers have explored multiple approaches to maximizing stable haze that will remain in suspension throughout the shelf life of the beer. Our recent investigations into yeast-dependent haze have uncovered specific brewing yeast strains that promote the formation of haze in heavily dry-hopped beer styles. These brewing strains have been termed “haze-positive” and furthermore, the timing of dry hop additions has been found to be another key factor in producing this stable haze. Classical genetics have identified YIL169C (herein referred to as HZY1) as both necessary and sufficient for the haze-positive phenotype in the yeast strain most widely used for Hazy IPAs. HZY1 encodes a candidate glycoprotein and our recent findings suggest it is localized to the cell wall through a GPI anchor. Surprisingly, using long-read sequencing data we uncovered extensive genetic variation in HZY1 across brewing strains. The haze-positive phenotype correlates with an expansion in the N-terminal serine-rich region. We propose that the Hzy1 glycoprotein is a critical component to yeast-dependent colloidal haze and the genetic variation in this locus contributes the range of haze phenotypes observed across industrial brewing strains.

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.

Quantification of Hop-Derived Bitter Compounds in Beer Using Liquid Chromatography Mass Spectrometry.

Hops (Humulus lupulus L.) are essential raw materials for beer brewing, and the major contributors to beer bitterness are isohumulones (iso-α-acids) and humulinones. In recent years, many breweries have focused on the production of hop-forward beer styles by adding hops after or during the cold fermentation stage, which will tend to release humulinones or other hop-derived bitter compounds. In this study, a LC-MS/MS method was developed for quantification of 60 hop-derived bitter compounds in 25 min. Reverse-phase chromatography with an alkaline methanol/acetonitrile (70:30) mobile phase was used for the separation. The quantitative range was 0.053-3912 ng/mL with correlation coefficient r > 0.99, and the LOQ were 0.26 and 0.053 ng/mL for iso-α-acids and humulinones. Precision (RSD < 5.0%) and accuracy (recovery 86.3%-118.1%) were both satisfactory. The abundance of hop-derived bitter compounds in the dry-hopped beer (Double-India Pale Ale) and the nondry-hopped beer (Vienna Lager) were monitored throughout the fermentation and storage stages, and the formation of oxidation and cyclization products showed difference profiles between these two beers. The quantification results reveal how hop-derived bitter compounds change throughout the brewing process, as well as the influence of hops and brewing techniques on beer bitterness.

Co-fermentation of lactic acid bacteria and S. cerevisiae for the production of a probiotic beer: Survival and sensory and analytical characterization

The effects of boiling stage hopping or dry hopping methods; the use of Bobek or Crystal hop varieties; and the usage of just Sacharomyces cerevisiae yeasts or co-fermentation with Lactobacillus plantarum bacteria on the production of a probiotic beer have been studied. Only the cell viability levels registered for Lactobacillus plantarum bacteria in those beers produced by dry hopping, after an initial inoculation of 10 million cells per mL in both beers hopped during the boiling stage and in dry-hopped beers, were higher than those generally considered as minimum to provide health promoting benefits. With regard to polyphenols, higher concentrations were generally obtained in the beers produced by co-inoculation, whereas with respect to volatile compounds, co-inoculation with Lactobacillus plantarum and the employment of the dry hopping method with Bobek hops resulted in the beers with the highest contents. The sensory profile of the beers was clearly influenced by the hopping method, so that dry-hopped beers were awarded significantly higher scores with respect to certain fruity (stone fruit and tropical fruit, p < 0.05) and floral descriptors (p < 0.05), while they were ranked at a lower level regarding their cereal and toasted descriptors. The hopping method was the most influential on the composition and sensory properties of the final beers whereas the co-fermentation did not substantially modify any of them.

Aroma Profile Development in Beer Fermented with Azacca, Idaho-7, and Sultana Hops.

Hops are among the most costly and environmentally impactful raw materials used in brewing, yet they play a crucial role in the aroma of beer. However, predicting beer aroma based on hop variety or hopping method remains arduous. This is partly because hop oils are unique for each hop variety, and they may be biotransformed by yeast enzymes during fermentation. Even slight molecular structure modifications can dramatically affect the organoleptic properties of beer. Through combined chemical and sensory analysis of dry-hopped beers prepared with different hop varieties (Azacca, Idaho-7, and Sultana), this work aimed to profile the aromas and the overall biotransformation processes taking place during fermentation. A total of 51 volatile organic compounds (VOCs) were semi-quantified and monitored: 19 esters, 13 sesquiterpenes, 7 ketones, 7 alcohols, 4 monoterpenes, and 1 volatile acid. There were significant similarities in the measured analytes and perceived aromas of these beers, but one hop variety (Sultana) delivered an increased quantity of unique aromas and an increased concentration of volatiles in the headspace for the same quantity of hop pellets added. This work provides practical information to brewers who utilize hops in beer production.

From Hop to Beer: Influence of Different Organic Foliar Fertilisation Treatments on Hop Oil Profile and Derived Beers' Flavour.

Foliar fertilisation is known to influence the physiological response of Humulus lupulus (hop plants), but its effect on the flavour profile of beer still has to be investigated. By comparing the effects of four fertilisation treatments, this study aims at determining whether different foliar fertilisation treatments have a significant impact on hop plants' aromatic quality and that of the beer produced. Hop cones harvested from each experimental treatment were brewed to obtain five single dry-hopped beers, which were subsequently analysed. Gas chromatography-mass spectrometry (GC-MS) and electronic nose (Cyranose 320) analyses were performed on the hop cones, while headspace solid-phase microextraction-gas chromatography-mass spectrometry HS-SPME-GC-MS, electronic nose and sensory analyses were carried out on the beers produced. The analyses not only allowed for a differentiation between the hops from the four fertilisation treatments and the control but also enabled a differentiation between the beers produced for their identification. Sensory evaluation revealed consumer preferences regarding the dry-hopped beers analysed, evidencing their distinctive features, including significant differences in both aroma and flavour.

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.

Effect of Czech Hop Varieties on Aroma of Dry-Hopped Lager Beer.

The hoppy aroma in beer is characterized by an overall pleasant profile. The impacts of five Czech hop cultivars, Rubin, Saaz, Vital, Harmonie, and Kazbek, were tested on the hop aroma of the resulting beers, compared with a control beer sample, which was hopped with a commercial hop extract during wort boiling. GC-MS analysis was used for the identification and quantification of aroma-active compounds in the hops and beer. Dry hopping was successful in terms of improving the hoppy aroma in beer. Odorants such as β-myrcene, linalool, geraniol, β-citronellol, humulene epoxide I, and 2-methylbutyl-2-methylpropanoate were found at higher concentrations than the control in all dry-hopped beers. To quantify the success of dry hopping, the transfer rates of hop odorants were calculated. Those of linalool, geraniol and humulene epoxide I were adequate, whereas the transfer rates of polar compounds, e.g., β-myrcene, were relatively low, mostly due to their polarity. Changes in hop oil constituents were clearly notable, with the generation of β-citronellol, the release of other terpene alcohols from their glycosides or oxidation of α-humulene. Yeast metabolism also played an important role in these changes.

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.

Changes in Diacetyl and Amino Acid Concentration during the Fermentation of Dry-Hopped Beer: A Look at Twelve Saccharomyces Species and Strains

Hops were traditionally used in brewing for the addition of isomerized alpha acids that balance the sugary wort with bitterness, though modern breweries are dry-hopping to add complex and unique aromas to their beers. An unintended consequence of high amounts of dry-hopping is the phenomenon known as hop creep, causing an increase in alcohol, carbonation, and diacetyl concentrations. The amount of diacetyl in a beer can be directly correlated to yeast health and vitality, controlled by the amount of free amino nitrogen (FAN) available to the yeast. In this study, both diacetyl and amino acid concentrations were measured prior to and 24 h after dry-hopping, at terminal gravity, and at the start of fermentation. These values were compared across twelve yeasts that are commonly used in dry-hopped beer or offer unique characteristics to fermentation. Experimental yeasts BY881, WLP518, K-97, and CK S102 all exhibited diacetyl concentrations below the aroma threshold for beer. The addition of dry-hops added a significant (p < 0.05) increase in FAN content to the fermenting beers, with most of the increases in serine, arginine, glutamate/glutamine, alanine, and glycine. These increases did not parallel the amino acid content measured in the grist or hops, where asparagine/aspartic acid, proline, and glutamate/glutamine were most prominent. Correlations between total FAN content and diacetyl concentration were calculated, as diacetyl is a precursor in the biosynthesis pathway of the amino acids valine and leucine. However, in this experiment, no correlation of amino acid and diacetyl concentration was observed between dry-hopped and traditional fermentations.

Why Catechin and Epicatechin from Early Hopping Impact the Color of Aged Dry-Hopped Beers while Flavan-3-ol Oligomers from Late and Dry Hopping Increase Colloidal Instability

Dry hopping imparts distinct aromas but also a series of non-volatile compounds suspected of causing flavor and physical instability during beer storage. In this work, color, chill haze, total polyphenols, total flavanoids, and flavan-3-ol monomers (catechin and epicatechin) and oligomers (procyanidin dimers and trimers) were monitored in five commercial pale-colored Belgian dry-hopped beers over 24 months of storage at 20 °C in the dark. Fresh dry-hopped beers contained unusually high levels of flavan-3-ol monomers (up to 6.6 mg/L) and oligomers (up to 14.1 and 10.2 mg/L dimers and trimers, respectively). The increase in color intensity during storage (up to 6.4°EBC) correlated with fresh beer monomer levels, while the oligomer content correlated with chill haze formation (up to 25.7°EBC). The evolution of these two physical attributes also correlated with the level of total polyphenols in the fresh beers. In a pilot-scale production, kettle hopping was shown to impart either monomers (early) or oligomers (late), while dry hopping promoted efficient extraction of both monomers and dimers (extraction yields of 62 and 74%, respectively). Dry hopping thus plays an important role in color and chill haze increase.

Characterization of bitter-tasting and antioxidant activity of dry-hopped beers.

Bitter flavors and antioxidant activities are critical characteristics and indicators, respectively, of beer quality. To gain a better understanding of dry-hopped beer's bitterness, this work comprehensively evaluated the perceived bitterness intensity and bitterness attributes from aspects of beer aroma and non-volatile bitter compounds using sensory analysis under two conditions: (i) with and (ii) without nose clips. To quantify bitter and volatile compounds, the work conducted chromatographic analyses: high-performance liquid chromatography (HPLC), ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) and gas chromatography-mass spectrometry (GC-MS). Simultaneously, this work assessed the antioxidant activity of commercially dry-hopped beers. First, dry-hopped beer in this study contained abundant non-volatile bitter compounds (hop bitter acids, polyphenols and flavonoids), and aroma was validated using HPLC, UPLC-MS and GC-MS methods. Moreover, the bitter-tasting perception test findings demonstrated that many dry-hopped beers had a higher bitterness intensity when evaluated without a nose clip, whereas this phenomenon was adverse in several ale beers. Additionally, the 'lingering' and 'harsh' characteristics were diminished when beer aroma was blocked out (with nose clip) for dry-hopped beer. Meanwhile, most dry-hopped beers had greater antioxidant activity than ale beers (P < 0.05). This work revealed the bitterness complexity of dry-hopped beer; besides non-volatile bitter compounds, beer aroma had an impact on the perceived bitterness intensity and attributes, and dry-hopped beer had a relatively intense antioxidant capacity. This study facilitated the development of a detailed knowledge about the assessment of bitter-tasting perceptions in dry-hopped beers and provided a basis for the development of functional beer benefiting human health. © 2022 Society of Chemical Industry.

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.