Dry Hopped Beers Research Articles

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.

Sensory and Olfactometry Chemometrics as Valuable Tools for Assessing Hops' Aroma Impact on Dry-Hopped Beers: A Study with Wild Portuguese Genotypes.

Sensory, olfactometry (using the sums of odour intensities for each class of compounds) and chemometric analyses were used to evaluate Portuguese wild hops’ sensory characteristics and the aroma that those hops impart to dry-hopped beer. CATA analysis and agglomerative hierarchical clustering was applied for the sensory characterization of 15 wild hops of Portuguese genotypes, clustering them in two groups: one more sulphurous, floral, and fruity, and another more earthy, resinous, floral, and non-citrus fruits. Two hops representative of each group were selected for the production of four dry-hopped beers using the same base beer style (Munich Helles). Beers were analysed by quantitative descriptive analyses and quantification of hop-derived key volatile compounds. Multivariate statistical treatment of the data was performed. Results indicate significant differences (p < 0.05) in fruity, resinous, earthy, floral, and sulphurous attributes of hops, but the dry-hopped beers only have a significant increase (p < 0.05) in fruity and spicy notes when compared with non-dry-hopped Munich-style Helles beer. Hop olfactometry explained the sensory perception that the 11 hops not used for brewing (employed as supplementary observations) are placed into the space of the odour-active compounds profile of the four hops selected for brewing. These 11 hop samples have more spiciness than fruitiness potential.

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.

Discovery of Bisulfite and an Uncharacterized Carbon-Centered Radical Systems in Non-Dry-Hopped and Dry-Hopped Beers Using a Different Spin Trap, 5, 5-Dimethyl-1-Pyrroline-N-Oxide, and a New Electron Paramagnetic Resonance Method

The amount of bisulfite (HSO3 −, hydrated SO2) needed in beer to extend flavor stability is controversial with results that show elevated HSO3 − levels in beer improves beer shelf-life analytically, yet decreases sensory flavor and flavor stability. Electron paramagnetic resonance (EPR) beer methods, using the N-tert-Butyl-α-phenylnitrone (PBN) spin trap, can detect the hydroxyl and ethoxy radicals from ethanol (•OH/CH3C • HOH). Water soluble 5, 5-Dimethyl-1-Pyrroline-N-Oxide (DMPO) trapped bisulfite (•SO3 -) and uncharacterized C-centered radicals in vastly different dry-hopped (DH) and non-dry-hopped (NDH-a and NDH-b) beers and can also trap radicals of nitrogen and oxygen. A new DMPO capillary tube method detected •SO3 - and C-centered radicals in cold stored and forced aged DH and NDH beers, dosed with 3 mM and 5 mM of sodium sulfite (Na2SO3), and displayed substantially higher •SO3 - radical signals from the 5 mM versus 3 mM Na2SO3 dosage. The lowest SO2 DH beer had greater polyphenols (antioxidants) and significantly less •SO3 - radical activity than the lower polyphenols NDH beers, indicating higher polyphenols in the DH beer quench more •SO3 - and uncharacterized C-centered radicals by way of H2O2 reduction. Increasing polyphenols and reducing beer SO2 levels can potentially improve beer flavor stability and reduce bisulfite allergies in humans.

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.

Changes in key hop‐derived compounds and their impact on perceived dry‐hop flavour in beers after storage at cold and ambient temperature

Changes in hop-derived compounds of beer were evaluated over 10 months of storage at 3 and 20°C, revealing significant changes in the beers stored warm. Beer pH and colour increased, together with ‘hop creep’ through storage of unpasteurised dry-hopped beers. Hop bitter acids decreased moderately during storage at 20°C but not at 3°C and hop aroma compounds - key contributors to dry-hop flavour - were significantly depleted upon warm storage. Cold storage resulted in significant retention of these compounds in the beers, especially hop mono- and sesquiterpenes which exhibited the greatest losses after warm storage. The losses of hop aroma compounds were linked in part to association with polymeric crown cap liners (‘scalping’), the dynamic of which was further impacted by storage temperature. A wide range of hop aroma compounds were found to be abundant in the crown cap liners of bottled beers after storage, in contrast to canned beers which showed better retention of key hop aroma compounds (caryophyllene, myrcene and humulene) throughout storage. The impact of some of the chemical changes during storage was determined by sensory analysis. Changes in ‘bitter’, ‘tropical’ and ‘citrus’ fruit, ‘sweet’ and ‘malty’ attributes were all influenced by storage temperature and the given beer. Changes in ‘floral’, ‘fruity’, ‘sour/acidic’, ‘alcoholic’ and ‘lingering aftertaste’ were dependent on the beer, whilst changes in ‘spicy’ notes were dependent on storage temperature. These findings provide meaningful insights into the storage induced changes of dry-hop flavour in dry-hopped beers. © 2021 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling.

Fate of Hop and Fermentation Odorants in Commercial Belgian Dry-Hopped Beers over 2 Years of Bottle Storage: Key-Role of Oxidation and Hop Esterases

The aim of the present work was to compare levels of short chain fatty acids, esters, terpenoids and polyfunctional thiols in (mostly bottle-refermented) commercial Belgian dry-hopped beers before and after 2 years of storage at 20 °C (the usual best-before date in Belgium). Among the hop-derived volatiles, the terpenoids linalool and geraniol, the polyfunctional thiols 3SHol, 3SHA and 3S4MPol, and the esters ethyl isobutyrate, ethyl isovalerate and ethyl heptanoate (up to 499, 53, 0.2, 2, 3, 84, 63, and 19 µg/L, respectively) were found above their sensory thresholds in most fresh dry-hopped beers. The fermentation-derived esters reached concentrations similar to those previously reported for non-dry-hopped beers, with ethyl hexanoate and isoamyl acetate (up to 0.4 and 3.9 mg/L, respectively) often above their sensory thresholds. Except ethyl isovalerate (more than 85% still present), most hop odorants and fermentation esters showed degradation over the 2-year storage period: only 45%–70% of linalool, geraniol, and ethyl hexanoate and even less than 40% for polyfunctional thiols, ethyl isobutyrate, and ethyl heptanoate initial concentrations were detected after storage. How the dry-hopping process affects this degradation was further investigated in model media. Fermentation esters proved to be more strongly impacted in dry-hopped than in non-dry-hopped beers because of hop esterase activity. In addition to being aware of the need to avoid hop esterases, craft brewers are here advised to use bottle refermentation for its ability to regenerate some flavors and consume packaged oxygen. No deleterious effect of yeast, such as short chain fatty acid excretion, was evidenced.

Hop-induced formation of ethyl esters in dry-hopped beer

Fruity smelling esters play an important role for the aroma of hops and beer and they have been characterized as key aroma compounds in different hop varieties. Studies on the transfer of hop-derived compounds into beer during dry-hopping showed calculated transfer rates of different ethyl esters far above 100%, leading to the assumption that these esters must be newly formed. To investigate this formation, dry-hopping was imitated in water to eliminate the influence of the beer matrix on the formation of these odorants. Thereby, the formation of ethyl esters of 2-methylbutanoic acid, 3-methylbutanoic acid, and methylpropanoic acid, induced by the addition of hops, was shown. Different approaches inhibiting enzyme activities and experiments with different hop extracts might lead to the assumption that enzymes are involved in the formation of these esters, beside possible transesterification.Graphical abstract

Impact of Copper Fungicide Use in Hop Production on the Total Metal Content and Stability of Wort and Dry-Hopped Beer

Transition metals, including copper, iron, and manganese, are known to catalyze the generation of reactive oxygen species (ROS) in beer leading to reduced product stability. Metals in beer are generally derived from raw ingredients. The present study aims to evaluate the impact of brewing and dry-hopping using hops treated with copper-based fungicides (CBFs) on the final transition metal content of model buffer solutions and pilot-scale systems of wort and beer. Copper levels in model wort and beer solutions were elevated (105.6% and 230.4% increase, respectively) when CBF-treated hops were used. In laboratory-prepared wort, elevated copper concentrations were not observed when CBF-treated hops were used for boiling. Dry hopping of beer using CBF-treated hops led to significant increases in total copper content (ca. 75 µg/kg vs. ca. 40–50 µg/kg in the control-hopped beer) when yeast was absent from the treated beer, but not when yeast was present. It was observed that manganese levels were significantly elevated in all hopped beers (ca. 495–550 µg/kg vs. 90–125 µg/kg in the unhopped control), regardless of hop treatment. A hop varietal thiol, 4-Mercapto-4-methylpentan-2-one, was spiked into treated beers, and the rate of oxidative loss was monitored during aging. Rates of thiol loss in treated beer samples did not differ across CBF treatments but were significantly lower in unhopped controls in the absence of yeast (p &lt; 0.0001) and correlated significantly with total manganese content of the beers (R2 = 0.4228, p = 0.0006). The rate of staling in hopped beers as measured by the rate of 1-hydroxyethyl radical generation did not differ among hop treatments, suggesting that excess copper content contributed from the hops does not negatively impact the oxidative stability of the beers. These findings suggest that brewers can use CBF-treated hops without any negative implications for the shelf stability of their beers and do not contraindicate the use of CBF in hops production when necessary.

Fate of Bitter Compounds through Dry-Hopped Beer Aging. Why cis-Humulinones Should be as Feared as trans-Isohumulones?

The evolution of isohumulones, main bitter compound of beers, through storage and its bitter impact has been studied for many years. With the uprising of highly hopped and, especially, dry-hopped beers during the last decade, other compounds such as humulones, cis-humulinones and hulupones have been shown to participate in both the sensory and measured bitterness of these beers. However, the fate of these compounds through aging is still unclear. The present work evaluated, by means of spectrophotometric and RP-HPLC-UV analyses, the evolution of bitterness units (BU), cis- and trans-isohumulones, humulones, cis-humulinones, hulupones, and tetrahydro-isohumulones in 21 Belgian dry-hopped beers after two years of storage. Besides the expected degradation of trans-isohumulones, it was observed an average decrease of 91% of humulones and 73% of cis-humulinones. Together, these results indicate a decrease of 18 – 43% of the calculated bitterness intensity of dry-hopped Belgian beers. The losses of cis-humulinones in dry-hopped beers bring seven new oxidation compounds, some of them very similar to those issued from trans-isohumulones. The bitterness impact of these compounds is yet to be determined.

Prediction of Fruity-Citrus Intensity of Beers Dry Hopped with Mandarina Bavaria Based on the Content of Selected Volatile Compounds

Mandarina Bavaria is a "Special Flavor" hop variety, described as fruity, with pronounced mandarin and citrus, combined with traditional hoppy sensations. The relationship between fruity-citrus intensity and the volatile profile of dry-hopped beers was assessed in order to predict the sensory perception of those dry-hopped beers using the content of selected volatile compounds. For this purpose, two base beers (A and B) that presented statistical differences (p < 0.05) in the composition of volatile compounds and on the sensory perception were dry hopped with 3 g/L Mandarina Bavaria hop. Twenty-four volatiles from hop were quantified during 15 days of dry hopping, while the sensory perception was followed by a certified trained panel. The sensory perception of total hoppy content (in a scale from 0 to 5) can be estimated using a PLS equation (Q2 = 0.654): total hoppy = 1.8 + [myrcene (μg/L) × 7.5 × 10-3] + [2-methylbutyl-2-methylpropanoate (μg/L) × 4.2 × 10-3] + [linalool (μg/L) × 7.2 × 10-3] + [α-humulene (μg/L) × 2.3 × 10-3]). Successful models were also obtained to predict citrus (Q2 = 0.745), green fruit (Q2 = 0.598), and sweet fruit (Q2 = 0.626) characteristics of dry-hopped beers.

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).

A Comparison of Single-Stage and Two-Stage Dry-Hopping Regimes

Multi-stage dry-hopping is a technique that is widely used by brewers to achieve intense hop aroma in beer. However, a thorough analysis of its efficacy does not exist in the published literature. The goal of this study was to compare the properties of beers produced by single or two-stage dry-hopping at the same cumulative rate. On the pilot scale (80–100 L), an un-hopped base beer was subjected alternately to single- or two-stage dry-hop additions at 386, 772, and 1544 g/hL using Centennial hops. Separately commercial beers (∼350 hL batch size) were dry-hopped at 733 g/hL in single or two-stage additions using a combination of Amarillo, Simcoe, Cascade, Citra, and CTZ pellets. Pilot scale dry-hopped beers showed increases in residual extract, pH, bitterness units, humulinones, and total polyphenols, accompanied by a decrease in iso-α-acids with increasing hop dose. Changes in bitterness units, humulinones, and iso-α-acids all appeared to be more pronounced in the two-stage dry-hopped beers. In contrast, commercial beers were nearly identical in terms of chemical composition. Significant increases in six aroma attributes scaled by a trained panel were observed as a result of two-stage dry-hopping in the pilot scale treatments. Slight increases in aroma potential were observed for the commercial beer made with two-stage additions, although these differences were not statistically significant. These results illustrate the impact multi-stage dry-hop additions have on beer aroma, and provide direction to brewers to consider whether multi-stage dry-hopping may yield desirable results while potentially using less hop material.

Evaluating the Impact of Dissolved Oxygen and Aging on Dry-Hopped Aroma Stability in Beer

It is generally recognized within the brewing industry that hop aroma and flavor in beer changes as beer ages post-packaging. Lager beer staling has been studied extensively, while dry-hopped beer has received limited attention. This study evaluated the impact of dissolved oxygen on the sensory and hop volatile profiles of dry-hopped beer during storage. Commercially-brewed dry-hopped beer was dosed with oxygen in a controlled fashion to create beers with a range of dissolved oxygen concentrations from approximately 40 to 250 μg/L 40 to 250 µg/L and then stored under chilled (3 °C) or accelerated (30 °C) storage conditions. Projective Mapping (Napping®) generated unique Euclidian configurations for each panelist, and ultra-flash profiling enriched the configurations with sensory descriptors. Sensory results identified storage temperature, used as a proxy for aging duration, as having the greatest effect on aroma during storage. Dissolved oxygen concentration was observed to have a lesser, but significant, impact at both high and low storage temperatures after only two weeks of aging. Higher temperature and dissolved oxygen concentrations resulted in decreased tropical, citrus, and hoppy characteristics and the expression of malty, dried fruit, and cardboard aromas. Hop derived monoterpenes were not significantly affected by treatment temperature or dissolved oxygen, suggesting stale character expression from alternate sources such as lipid oxidation or Strecker aldehydes formation.

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.

Investigating the Factors Impacting Aroma, Flavor, and Stability in Dry-Hopped Beers

Investigating the Factors Impacting Aroma, Flavor, and Stability in Dry-Hopped Beers

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.

Modeling of α-acids and xanthohumol extraction in dry-hopped beers.

The practice of dry-hopping has been used by the brewing industry to obtain beers with increased contents of flavor and bitterness compounds. Notwithstanding this, other compounds such as α-acids (AA) and xhanthohumol (XN) are co-extracted influencing the final characteristics of the beer, particularly its beneficial bioactivity. In this context a model for the understanding of AA and XN extraction by dry-hopping is proposed. The varieties Chinook (CHI), East Kent Goldings (EKG) and Tettnanger (TET) were assayed and robust statistical approaches were applied for data interpretation. Concentration of AA in beers post-maturation reached values higher than 20 mg/L using 2.8 g/L of CHI hops and 10 days of maturation. For XN, a similar behavior was verified. The maximum efficiency of AA and XN extraction (transfer rate) were reached at 13.5 days with dose rates of 147 and 13.9 mg/L, respectively.