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Extraction Efficiency of Dry-Hopping
Abstract
Dry-hopping, which is the cold, aqueous extraction of hops into beer, has gained popularity in recent years as a method for achieving intense hop aroma and flavor in beer. With some brewers dry-hopping at rates up to 2 kg/hL (60 hL (50 bbl) of beer at a rate of 1,592 g/hL (4.125 lb/bbl). Approximately one-third of the dry-matter composition of hops was lost during dry-hopping regardless of hop variety; however, there was high retention of both a-acids (77% pilot scale, 52% industrial) and hop essential oil (51% pilot scale, 33% industrial). The oil remaining in the spent hops was enriched in hydrocarbon compounds and depleted in oxygenated compounds. These results indicate that spent dry-hops contain considerable brewing value and have the potential for re-use.
... [27] Dry hopping is a rather inefficient process in which major volatile (i.e., myrcene) and nonvolatile (i.e., humulones) hop compounds are poorly transferred into beer. [28] The transfer of nonpolar compounds such as terpenes and sesquiterpenes (i.e., myrcene, β-caryophyllene) from hops into beer ranges from only 1-10% [29][30][31][32] in static dry hopping and can be slightly accelerated and increased by dynamic dry hopping. [29,33] Terpenoids (i.e., linalool, geraniol & nerol > 40% [29,[31][32][33] ) typically dissolve slightly better when compared to terpenes, although extraction rates differ remarkably depending on dry-hopping and experimental set-up. ...
... [28] The transfer of nonpolar compounds such as terpenes and sesquiterpenes (i.e., myrcene, β-caryophyllene) from hops into beer ranges from only 1-10% [29][30][31][32] in static dry hopping and can be slightly accelerated and increased by dynamic dry hopping. [29,33] Terpenoids (i.e., linalool, geraniol & nerol > 40% [29,[31][32][33] ) typically dissolve slightly better when compared to terpenes, although extraction rates differ remarkably depending on dry-hopping and experimental set-up. Hop bitter acids, with the exception of humulinones, [34][35][36] are poorly transferred into dry hopped beer (transfer rate 1-32%) which is due to their low to moderate solubility in beer. ...
... The presence of iso-humulone in spent hops was confirmed by Cocuzza et al. [35] who found about eight times more iso-humulone in dried spent hops than in the dry hopped beer. Hauser et al. [31] determined an average retention rate of 77% for humulones in a static lab-scale dry hopping experiment. Spent hop samples from four industrial scale batches (identical dry-hopping protocol) retained approx. ...
... Normally, hop doses are between 200 and 800 g/hl. But many American craft breweries use extremely high doses of hops reaching up to 2200 g/ hl for dry-hopping [1]. The dry-hopping technique is associated with a pleasant and generally distinctive raw hop flavor in beer. ...
... This operation is the extraction of hops with a weakly alcoholic aqueous solution. Hop volatiles, polyphenols and α-acids and oxidation products of α-acids (humulinones) and β-acids (hulupones) pass into the solution [1,4]. Dryhopping increases the pH and the bitterness, and reduces the iso-α-acids (adsorption onto hop plant material) [3,5]. ...
... Depending on the conditions of dry-hopping (alcohol content, temperature, flow, contact time, dose, and hop variety), not only the content of the components of hop volatiles, but also their composition changes [1,3,12]. As a result, these factors cause different flavors in dry-hopped beer, even when using the same hop variety [4,13]. ...
Dry-hopping is widely used by breweries of all sizes to achieve an intense hop aroma. Static (5-day) and dynamic (120-min) dry-hopping was compared in single variety pale lager brews. GC/MS was used to monitor the extraction kinetics of hop volatiles during the process. The hop-related aroma and bitterness profiles of the final beers were evaluated. The dynamic procedure resulted in a higher concentration of some hop volatiles, hop α-acids, and polyphenols in beer. The bitterness profile of the beer did not differ significantly. The maximum yield of hop volatiles was obtained in 2 days of the static process. The concentration of volatiles increased during the entire time of the dynamic process. The hop-related aromas intensity profile in beer depended on the dry-hopping method in combination with the hop variety. Multiple factor analysis (MFA) of the normalized data of volatiles concentrations and hop-derived aroma scores from the final beers revealed a relationship between some volatiles and hoppy, citrus and herbal attributes, and in general a higher volatile concentration and aroma intensity were observed with dynamic dry-hopping. The benefits of the dynamic dry-hopping approach can be higher yields of some hop volatiles, shorter time, and better process control. For both methods, it is necessary to adjust the contact time to create a certain aroma profile associated with hops.
... The focus of the studies are on different brewing parameters such as flowers or pellets (Ceola et al., 2019), contact time and temperature (Oladokun et al., 2017), and methods of dry (Podeszwa & Harasym, 2016;. Other awareness raised and researched are the ones concerning environmental and health hazard issues, such as presence of pesticides in hops and whether they can be found in beer (Kippenberger et al., 2014) and reuse of DH spent hops (Hauser et al., 2019). ...
... Hop spent had 33% of AA in pilot scale and 48% in industrial scale, and half of hops essential oil in pilot scale, and two thirds in industrial. This means that many useful aroma and bitter compounds in the spent hops can be still used, either as material for another batch (Hauser et al., 2019) or for hop products. ...
... Hop aroma composition in DH beer is composed of thousands of different substances, each of which has individual properties in terms of sensory qualities, solubility, volatility, and polarities. Recent studies demonstrated that part of the products discarded in the dry hopping process retains valuable volatile and nonvolatile components of hops, this opens up the possibility of recovering both the bitter and aromatic potentials of what would otherwise be a residue of the production process (Hauser et al., 2019). Based on this, the chosen dry hopping technique can minimize such losses in this step. ...
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.
... The essential oil fraction in hops contains over 1000 different compounds, with around 440 compounds being identified [24,25], and with most of the compounds having effects on aroma and flavour at subthreshold concentrations [26]. Hop varieties with higher essential oil contents are commonly correlated with increased levels of monoterpenes, mostly myrcene relative to sesquiterpenes (caryophyllene and humulene) [27]. ...
... Hop varieties with higher essential oil contents are commonly correlated with increased levels of monoterpenes, mostly myrcene relative to sesquiterpenes (caryophyllene and humulene) [27]. An increase or decrease in specific hop volatile component levels within the essential oil and the identification of reaction compounds can be used to evaluate the freshness and quality of hops [25]. ...
The increased use of aroma hops for dry hopping has become a common technique used by brewers to impart hoppy aromas and flavours into beer. The increased demand for aroma hops has led to hop quality becoming more important. Brewers want to ensure the freshest hops are used, however the quality of hops can decrease during storage. The common hop quality indicator is hop storage index (HSI). In this study, two varieties of hops (Citra ® and Galaxy ®) with three different HSI classifications: fresh (< 0.32), aged (0.41-0.50) and over-aged (> 0.61) were evaluated. A pale ale was brewed and dry hopped with each variety at the different HSI classifications. The key aim was to assess the impact of HSI on total oil content and beer quality in terms of hoppy aroma and flavour quality. The total essential oil content and profile of hop oil components were analysed. Sensory and analytical analysis was conducted on all beer samples. The total essential oil content decreased as the HSI increased. The increase in HSI changed the profile of hop oil components causing significant decreases in myrcene and leading to an increase in oxidation components such as caryophyllene oxide, humulene epoxide I and humulenol II. Increase in the vegetal attribute for both varieties were significant, most likely due to the formation of sulphur compounds. Bitterness intensity and perceived bitterness increased as the HSI increased, whereas the bitterness quality was reduced. Humulinone concentration in beer increased alongside the HSI value. Beers dry hopped with hops which had a HSI value > 0.41 led to aroma, flavour and bitterness deviations in comparison to beers brewed with fresh hops. While HSI doesn't measure total oil content of aged hops, it does have a negative correlation on the total essential oil content, indicating that the hop quality has deteriorated.
... Hops used in this manner are typically filtered out of beer and discarded as waste; however, recent studies have revealed that they still contain high concentration of alpha-acids (humulones) as well as volatile compounds. This demonstrates that hops used for dry-hopping could potentially be recycled to kettle-hop beer, reducing resource waste and lowering beer production costs (Hauser, Lafontaine, & Shellhammer, 2019). The goal of this study was to assess how substituting normal hop pellets with recycled hop pellets (previously used to dry-hop another beer) affected beer bitterness and other beer qualities like content of volatiles, phenolic compound concentration, and antioxidant activity. ...
... IBU of B2A1, where half of the hop material (portion used for bittering) was substituted with recycled hops, was decreased by 26% to 15.25, and IBU of B2A2, brewed only with recycled hops, was 14.32, which was 31% lower than IBU of B1A1. These findings are consistent with a study on the extraction efficiency of dry hopping conducted by Hauser, Lafontaine, and Shellhammer (2019), which discovered that hops previously used for dry hopping can retain up to 77% alpha-acids. These findings show that brewers can achieve adequate bitterness while using only hops recycled from previous batches of dry-hopped beer by carefully adjusting the dosage of recycled hops. ...
Dry-hopping process is the cold extraction of substances found in hops into beer. This method has gained popularity among beer brewers in recent years because it aids in the introduction of intense flavour and aroma into fermented beverages. However, using a large amount of hop material may result in significant losses of spent hops and beer. In this study, test batches of beer hopped with recycled hops were made with varying dosages of recycled material. Beers brewed with recycled hops had lower IBU (international bittering units) and lower concentrations of hop-derived volatiles (such as aromadendrene, α-terpineol, methyl geranate and α-caryophyllene), but they retained the same level of antioxidant activities (assessed by ABTS∙⁺, DPPH∙ and FRAP assays), concentration of phenolic compounds and many yeast-derived volatile metabolites as the model beer (hopped with new hops) and acquired higher notes for taste parameter in the sensory analysis.
... [9] In subsequent research, Kirkpatrick and Shellhammer reported that hop creep is caused by low but continuous activity of several starch-degrading enzymes (amyloglucosidase, α-amylase, β-amylase, and limit dextrinase) present in Cascade hops. [10] Recent research has also focused on the dry hopping process parameters and their influence on the aromatic profile of beer [11][12][13][14][15] and beer stability. [16][17][18] Jobe et al. explored the extent to which growing conditions such as location, soil properties and composition, farm management, and climate may impact the dextrin-reducing enzymatic activity of hops. ...
... In contrast to addition at the end of the boiling step, dry hopping is a cold extraction of hop at the end of fermentation or during maturation. This technique improves aroma-related compounds extraction, but also the oxidative stability of beer [36,37], making it a valuable tool for breweries to increase resource conservation, e.g., enhancing the efficiency in the use of hops. Hop pellets used for dry hopping may be reused for further hopping. ...
Beer production consumes significant amounts of water, energy, and raw materials, and results in the production of various by-products, including wastewater, brewers’ spent grain, yeast and hop. To lower its environmental footprint, by-products may be reclaimed or valorized in agro-food, cosmetic, material, chemical industries, etc. According to most recent research, breweries have the potential to become biorefineries, as they can extract diverse valuable plant-based compounds such as carbohydrates, proteins, lipids, phenolic compounds, platform chemicals, and biopolymers. These biomolecules possess bioactive and physicochemical properties, which can be enhanced through recovery processes. Brewery by-products may be utilized in various industries within the bioeconomy frame. In agro-food systems, extracts can increase final products’ techno-functionalities. Such additives can also help in creating marketing labels such as clean-label healthy, which can further attract potential customers. Businesses can gain economic and socio-environmental benefits by implementing sustainable practices, which can also improve their corporate image. This article outlines recent advancements in the processing and valorization of brewery by-products, ultimately defining an up-to-date, sustainable strategy for clean beer production.
... European hop varieties, on the other hand, exhibit lower myrcene content, falling within the 20% to 40% range (Nesvadba et al., 2021). Myrcene contributes to a range of aroma properties, often described as green and hoppy with hints of pine and citrus, influencing modern brewing techniques like "dry hopping" (Hauser et al., 2019;Rettberg et al., 2018;Nance et al., 2011). Figure 4 displays the content and variability of myrcene in Ukrainian hop varieties studied. ...
The aim of the study was to evaluate the variation in essential oil content and composition within nine distinct Ukrainian hop varieties, with a particular focus on their genetic stability and suitability for brewing applications over 11 years of their cultivation. The hydrodistillation method (Analytica-EBC 7.10) was used to evaluate hop essential oil content and gas-liquid capillary chromatography (Analytica-EBC 7.12) to discern its qualitative composition. Variability was evaluated using statistical parameters. The essential oil content across the studied varieties spanned from 0.51 to 2.58 ml/100 g of dry hop cones. The highest content was measured in the bitter-aroma variety with a special aroma – Ruslan. The predominant essential oil components, including myrcene, caryophyllene, humulene, and farnesene, collectively constituted 70.0–84.2% of the total amount. The aroma varieties displayed myrcene content typical for European varieties (with the level up to 56.2% in the Ruslan variety). Farnesene content exhibited significant variation ranging from 0.3 to 17.6% with the highest content in Saaz-type varieties (Klon 18, Zlato Polissya, and National) and the bitter type Promin variety. Humulene content ranged from 13.2 to 32.6%. Among all studied varieties, Alta displayed the least variability for all parameters evaluated (Cv = 15.2%). This study underscores the genetic basis of essential oil composition in hops, emphasizing its potential as a biochemical criterion for identifying hop breeding varieties. The study revealed, that despite annual fluctuations, the essential oil content and composition remained within passport data declared for the variety. The findings provide valuable insight into a sustainable cultivation and optimal utilization of hops in the brewing industry.
... The solubility of the terpene alcohols due to their polar characteristics promotes their transfer into beer, while for non-polar compounds, such as myrcene the extraction occurs to a limited extent (Forster & Gahr, 2013). Brewers in order to improve the oil extraction and enhance the beer aroma and flavour can modify several factors during dry-hopping, such as dosing time, contact time, static or dynamic extraction, the temperatures, the type of hop products, the hop varieties, and the hopping amounts (Förster et al., 2013;Hauser, Lafontaine, & Shellhammer, 2019;. ...
... The resulting sensory effect of dry hopping beer depends on a number of raw material and technological factors, hop variety, hop dose, hop contact time with beer, method of hop application (static batch or dynamic flow process), technological operation (application to young beer, filtered beer) and last but not least, the type of beer and the matrix of sensory active substances derived and not derived from hops in the starting beer before dry hopping (Steenackers et al., 2015;Algazzali and Shellhammer, 2016;Hauser et al., 2019;von Heynitz et al., 2020;Bandelt Riess et al., 2020). ...
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.
... Polar compounds, such as linalool pass to the beer in large quantities, while non-polar compounds, such as myrcene are found only in trace amounts, mainly due to their low solubility. In a study conducted by Hauser et al. (Hauser et al., 2019), spent hops used for 24 h dry hopping contained 77% of the original essential oil content The concentration of terpene and sesquiterpene hydrocarbons decreased only slightly, while the levels of oxygenated compounds like terpene alcohols and aldehydes decreased up to 10% of the original amount. Factors such as beer temperature, contact time, use of mechanical agitation, fermenter size, alcohol size and IBU levels are known to have a significant impact on the extraction levels during dry hopping. ...
Besides providing bitterness to beer, hops also impart a whole range of aromas, such as herbal, spice, floral, citrus, fruity and pine to this beverage. Although hops are usually added in relatively small amounts, they have a significant impact on the sensory characteristics of the product. Raw hop aroma significantly differs from the aroma resulting from its addition to the beer. The final aroma of the beer arises from substances in the malt, hops, other additives, and yeast metabolism. The biochemical transformation of hop compounds by yeast has become more and more popular in recent years. Knowledge of this process may allow more precise control over the final sensory characteristics of the beverage. The article describes the chemical composition of hops and discusses the influence of the hopping regime on the concentration of volatile compounds in the finished product. Moreover, the article describes the biotransformation of hop-derived compounds by traditionally used Saccharomyces cerevisiae yeast, as well as less commonly used non- Saccharomyces yeast. The paper outlines the current state of knowledge on biotransformation of hop-derived hydrocarbons, terpenoids, esters, sulfur compounds and glycosidically bound aroma precursors.
... Several factors influence the effects of dry hopping. However, most studies have focused on the process parameters that provide the best aroma effects (Hauser et al., 2019;Lafontaine & Shellhammer, 2018;Oladokun et al., 2017;Wolfe, 2012). Hops are rich in polyphenols (approximately 2-8% weight by weight [w/w] of dry weight) (Kammhuber, 2005;Roberts et al., 2006) and metal ions (Helin & Slaughter, 1977). ...
Electron spin resonance (ESR) spectroscopy was used to determine the effect of dry hopping on the oxidative stability and antioxidative potential of beer. Commercial beer was dry-hopped at 5 °C and 20 °C with six hop varieties (Polish and American). The rate of radical formation and lag time were found to depend on the variety of hop used. An increase in the lag time and a decrease in the rate of radical formation occurred when dry-hopping was performed at 20 °C for all hop varieties (at 5 °C in some varieties). The lag time had a strong correlation with the TPC (total polyphenols content) in beer. The rate of radical formation was correlated with the iron content of the beer. A decrease in iron concentration was observed after dry-hopping at 20 °C. Overall, the evaluation of free radical formation using ESR is useful for predicting oxidative changes in beer during storage.
... They all have one characteristic in common: the hops are added in the desired concentration to the respective tank where they are extracted according to the grams added per hectoliter, at the greatest possible concentration gradient for the respective aroma compounds. While hop additions of a few hundred grams per hl were still common, especially in the first half of the last century [5][6][7], additions of over 2.2 kg/hl are practiced today [8,9]. ...
An approach to develop an external dry hopping method by restoring the aroma transfer through dilution This work encompassed testing the impact of high mass concentrations of substances on the transfer of aroma and bitter compounds during dry hopping. For this purpose, a novel dynamic process for the production of cold-hopped beers was implemented on a laboratory scale. In this process, a suspension of hops and beer with a high concentration of 6.5 % w/w hops is prepared and diluted to 1.5 % w/w with beer. Then, the particulate matter is immediately separated from the beer using a filter. Evaluation of the bitter compounds, terpenes, esters and thiols using analytical methods indicated that the transfer of these compounds during dry hopping occurred similarly in samples which were hopped at the higher rate and subsequently diluted compared with those hopped at 1.5 % w/w but were not diluted. In sensory trials conducted by a panel of trained tasters (n = 10), no significant difference up to a significance of α = 0.20 could be detected by means of discriminative testing. Furthermore, no significant difference (α = 0.05) was found between the attributes of the beers in descriptive testing.
... Regardless of when brewers dry-hop beer, the volatile aromatic compounds responsible for hoppiness tend to have poor transfer rates to cold beer. [2] Due in part to the large amounts of hops used during dry-hopping, their effect can lead to unexpected and undesirable outcomes because hop-associated enzymes can degrade unfermentable dextrins remaining in fermented beer to fermentable sugars, thereby triggering refermentation. [3,4] This refermentation is often very slow and thus is colloquially called "hop creep" by American craft brewers. ...
To investigate potential sources for field-to-field variation in hop diastatic power, three varieties of hops (Mosaic®, Simcoe®, and Strata®) from harvest year 2019 were collected from different fields managed by a single hop grower throughout the hop growing region within Oregon’s Willamette Valley. Fields for this study were selected based on soil type and weather patterns, and eleven fields were identified for sampling (3 Mosaic®, 3 Strata®, and 5 Simcoe®). Farm management data on fertilization rates and pesticide applications were collected by the grower (Coleman Agriculture). Using USGS soil maps, five individual sites within each field were identified for soil sampling, and hop bines near those sites were GPS tagged and hand harvested when they were at similar maturities. After harvest, the hops were analyzed for enzymatic activity using an HPLC method. The relationships between hop enzymatic activity and the farm management, soil, and weather data yielded associations with soil texture, growing degree day accumulation, fertilization practice, and pesticide application. The data also suggest a potential link between hop diastatic power and downy mildew (Pseudoperonospora humuli) or powdery mildew (Podosphaera macularis) infection. The links between hop diastatic power and agronomic variables will allow farmers to minimize hop creep potential in the hop field thereby potentially mitigating the effects that brewers see in the cellar.
... Furthermore, because the addition occurs in cold fermenting wort or beer, there is no isomerization of alpha acids and thus the dosage rates can be considerably higher than kettle or late/whirlpool hopping. This is useful as the dry-hop dosage rates need to be quite high in order to extract the desirable volatile aromatic compounds, which generally have low transfer rates into beer [7]. These volatile aromatic compounds are desirable, as they can lend a tropical, lemon, herbal, pine, or any one of a variety of other aromatic characters to a beer [6,8]. ...
Dry-hop creep is a gradual reduction in beer gravity after dry-hopping in the presence of yeast due to generation of fermentable sugars from nonfermentable dextrins by hop-associated enzymes. A benchtop forced fermentation-based method for estimating the dextrin reducing potential of hops during dry-hopping is proposed and evaluated for feasibility. In this paper, forced fermentations are compared to paired 2 hL pilot full-scale fermentations in order to evaluate how well a benchtop method will reflect the changes observed due to hop creep in a full-scale fermentation. The forced fermentations proceeded much more rapidly than the full-scale pilot fermentations, and apparent extract and apparent degree of fermentation correlated well between the dry hopped forced fermentations as measured at 72 hours and the terminal values of the full-scale fermentations. Results indicate that a small-scale dry-hopped forced fermentation is a promising tool for assessing the potential magnitude of hop creep in a given lot of hops, and that differences in apparent extract and/or apparent degree of fermentation of forced fermentations can be used to estimate the terminal gravity post-hop creep of full-scale fermentations.
... The typical hop aroma in beer is mainly caused by volatile hop oils, accounting for 0,5 -3 % of the dry matter of hops [2]. The oil consists of hydrocarbons (mainly terpenes and aliphatic hydrocarbons), oxygenated hydrocarbons (mainly terpenoids like geraniol or linalool) and sulphur compounds [3,4]. This variety of ingredients leads to the distinct hop aroma intensity in beer and especially in dry hopped beers [5]. ...
Dry hopping can be described as a heterogeneous solid-liquid reaction, calling for high mass transfer rates, low resource consumption, and effective phase separation. This work presents a model-based feasibility analysis of a novel approach to dry hopping that addresses these requirements: the planetary rotating bed reactor (PRBR). This solid-liquid reactor is kinematically enhanced by a planetary gear derivate. The superposition of two rotary motions results in an oscillating acceleration that generates a push-back effect on the hop solids contained in the reactor chamber. Clogging of the retaining filter mesh can thereby be prevented while maintaining high relative flow velocities between hop solids and the circulating beer to promote the desired mass transfer. In this work, a 2D simulation model of the system kinematics is implemented in MATLAB ®. The model is governed by a set of analytical equations, allowing for high accuracy and low computational effort. Trajectories and accelerations of relevant reactor segments are calculated, considering design and process variables like gear diameter and rotation speed of the input shafts. The existence of the underlying push-back effect and its technical viability are verified and evaluated by appropriate performance indicators in consideration of the fluid throughput. As a result, the PRBR promises to be a fast, hop-saving and fully scalable solution for dry hopping and other heterogeneous reactions.
... Hop-forward beer styles such as India Pale Ale (IPA), the production of which within the American craft beer market has increased nearly 10-fold over the past decade, call for considerably more hop material (12). The majority of these hops find their way into beer as dry hops, which are inefficiently utilized in terms of both bitterness precursors and aroma compounds (13)(14)(15)(16). Residual hop bitter acids have been shown to be an effective source of hop bitterness upon reuse of dry hops during wort boiling (17). ...
As public awareness of anthropogenic climate change grows and consumers demand more sustainably produced products, it is imperative that the beer industry implements more sustainable production processes. Fortunately, there is a growing body of work related to the sustainability implications of beer production, which can help to advise brewers in decision making toward better environmental stewardship. From the life-cycle perspective, inputs both upstream and downstream of the brewhouse, such as packaging production and retail refrigeration, can often have significant bearing on the environmental impact of a given brand. From the perspective of environmental sustainability, malted barley often garners the most attention among beer ingredients, because its production process is highly energy intensive; it is typically the largest ingredient (aside from water) in beer recipes, and it has the potential to be valorized as a coproduct. Hops gain less attention and are often overlooked, because the bulk of the literature focuses on lager style beer, for which hops are used only in sparing quantities. However , the recent surge in popularity of hoppy beer styles has driven brewers to use ever-increasing quantities of hops in the quest for intense and unique hop aroma, with the consequence that the sustainability implications of hops production can no longer be neglected.
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.
. In Ukraine, hops are basically processed into Type 90 pellets, that are practically indistinguishable in terms of biochemical indicators from hop cones. Pellets of hop are the single domestic source of hop products that can be serve as an alternative to imported pellets and extracts that used in the Ukraine brewing. Comprehensive studies of the evaluation of Type 90 hop pellets of aromatic and bitter varieties produced in Ukraine and European countries allowed establishing that they have different biochemical compositions and consequently, different brewing value. That have been identified differences in the absolute values of indicators such as the mass fraction of alpha acids, beta acids and their composition, xanthohumol, essential oil, the ratio of valuable hop compounds: beta acids to alpha acids and components of the essential oil. It has been determined that in hop pellets of aromatic varieties, the content of alpha acids changing from 3.3% in the Klone 18 variety to 5.9% in the Hallertauer Tradition variety. The content of beta acids, in the investigated pellets, ranges from 3.6% (Klone 18) to 6.7% in the Slavyanka variety. It is established that the hop pellets made from Ukrainian varieties Zagrava and Slavyanka have significantly higher content of beta acid 6.3% and 6.7%, respectively, compared to pellets of foreign varieties. There is a significant advantage in the resin fraction of beta acids over the fraction of alpha acids in the pellets of Slavyanka, Klone 18, Zhatetsky and Zagrava varieties, that they meaning retain a positive coefficient of aromaticity between the content of beta and alpha acids that ranges from 1.18 to 1.37. The content of alpha acids ranges from 8.7% in the Polisky variety to 14.1% in the Magnum variety in the hop pellets of bitter varieties. The content of beta acids in the same pellets ranges from 4.2% to 5.9%. It has been established that the composition of alpha and beta acids in the investigated pellets changes depending on the variety. It has been proven that Ukrainian-produced hop pellets correspond to their international counterparts in terms of their characteristics. Specifically, the biochemical and technological indicators of Klone 18 hop pellets correspond to the characteristics of pellets of the Czech variety Zhatetsky, pellets made from the bitter variety Alta correspond to the biochemical indicators of German Magnum pellets but pellets of varieties such as Slavyanka and Zagrava exceed the world analogies in terms of the composition and quality of bitter substances and essential oil. Based on the comparative biochemical characteristics of Type 90 hop pellets of Ukrainian and European production, the quality of Ukrainian hop products has been found to be at a global level. Certified domestic hop products, specifically Type 90 pellets, can be used do not only by Ukrainian brewers but also by other manufacturers to create new innovative and competitive products with various functional purposes.
Мета. Визначити пивоварну якість гранул хмелю тип 90 українського виробництва та встановити їх конкурентоспроможність на основі біохімічної і технологічної оцінок. Методи. Фізикохімічні — для визначення показників якості гранул хмелю, спеціальні і загальноприйняті в хмелярській галузі, математикостатистичні та методики Європейської Пивоварної Конвенції, зокрема високоефективна рідинна хроматографія, капілярна газова хроматографія, кондуктометрія, спектрофотометрія. Результати. Дано біохімічну оцінку гранул хмелю тип 90 українських сортів Клон 18, Злато Полісся, Альта за кількістю та складом гірких речовин, ефірної олії та проведено їх порівняння із зарубіжними гранулами сортів Жатецький (Чехія) та Магнум (Німеччина). Відзначено, що в гранулах хмелю ароматичних сортів уміст альфакислот змінюється з 3,7% у сорту Клон 18 до 4,5% у гранулах сорту Жатецький. Уміст бетакислот у досліджуваних гранулах становить від 4,4% (Злато Полісся) до 6% у гранулах сорту Жатецький. У смолах гранул сортів Клон 18, Злато Полісся та Жатецький частка бетакислот є значно вищою, ніж частка альфакислот, тобто в них зберігається позитивний коефіцієнт ароматичності між умістом бета та альфакислот, що становить 1,16–1,30. У гранулах тонкоароматичних сортів уміст когумулону — 24,6–26,0%. У гранулах хмелю гірких сортів уміст альфакислот змінюється з 9,7% у сорту Альта до 16,0% у сорту Магнум. Уміст бетакислот у цих самих гранулах становить від 5,5% у сорту Альта до 7% у сорту Магнум. Уміст когумулону змінюється в діапазоні від 23,5% у гранулах сорту Альта до 29% у гранулах сорту Магнум. Доведено, що гранули хмелю українського виробництва за своїми характеристиками відповідають світовим аналогам. Висновки. Установлено, що проаналізовані гранули хмелю тип 90 українського виробництва не поступаються за якістю зарубіжним гранулам і мають перспективу широкого використання в пивоварінні, забезпечуючи високу якість пива.
Dry-hopping is the addition of hops to the wort on the cold side of the brewing process. Unlike standard hop additions, its main purpose is not to produce a characteristic bitterness but to extract as much of the hop essential oils as possible, which are largely lost in the standard hopping process. When dry-hopped, it is possible to obtain a beer with an aroma that is difficult to achieve when hops are used on the hot side of the brewing process. As a result, this process has become very popular in recent years, particularly in beers that belong to the ‘craft beer revolution’ trend. In addition, the usefulness of this process is increasing with the development of new hop varieties with unique aromas. This article presents the main components of hops, focusing on those extracted during the process. Changes in the composition of beer bittering compounds and essential oils resulting from this process are discussed. This paper presents the current state of the knowledge on the factors affecting the degree of extraction, such as hop dosage, the time, and temperature of the process. Issues such as process-related physicochemical changes, hop creep, low flavor stability, haze formation, and green flavor are also discussed.
There is a growing appreciation for the role that yeast play in biotransformation of flavour compounds during beverage fermentations. This is particularly the case for brewing due to the continued popularity of aromatic beers produced via the dry-hopping process. Here, we review the current literature pertaining to biotransformation reactions mediated by fermentative yeasts. These reactions are diverse and include the liberation of thiols from cysteine or glutathione-bound adducts, as well as the release of glycosidically bound terpene alcohols. These changes serve generally to increase the fruit and floral aromas in beverages. This is particularly the case for the thiol compounds released via yeast β-lyase activity due to their low flavour thresholds. The role of yeast β-glucosidases in increasing terpene alcohols is less clear, at least with respect to fermentation of brewer’s wort. Yeast acetyl transferase and acetate esterase also have an impact on the quality and perceptibility of flavour compounds. Isomerization and reduction reactions, e.g. the conversion of geraniol (rose) to β-citronellol (citrus), also have potential to alter significantly flavour profiles. A greater understanding of biotransformation reactions is expected to not only facilitate greater control of beverage flavour profiles, but also to allow for more efficient exploitation of raw materials and thereby greater process sustainability.
Key points
• Yeast can alter and boost grape- and hop-derived flavour compounds in wine and beer
• β-lyase activity can release fruit-flavoured thiols with low flavour thresholds
• Floral and citrus-flavoured terpene alcohols can be released or interconverted
Beer is a popular drink and represents the most widely consumed alcoholic beverage in the world. In recent years, there has been a significant growth of independent craft breweries, even in countries without a brewing tradition.
A craft brewery is usually defined as a small, independent and traditional brewery.
Nowadays, consumers are looking for genuine, singular, different and high-quality products. Craft beer manufacturers have responded to this with the introduction of a novel combination of raw or malted cereals and have modified the beer flavours and taste with the addition of fruit, spices, etc.
This work presents an analysis of the different aspects related to craft beer. Its characteristics and brewing singularities are analyzed. The quality and safety standards used are examined and future trends of craft beer are also discussed.
Mead is a fermented product from honey bees. This alcoholic beverage is recognized as one of de oldest onsumed by man and archaeological evidence of its production dates back to 7000 BC. It is popularly produced at home and/or in small factories. The raw material has great influence on the quality and characteristics found in the final product, and different types od mead can be distinguished based on the kind od honey and the producer bees, honey/water ratio, addition of spices and/or fruits, yeast utilized, method of the must preparation, maturation and aging. Mead prodction has increased remarkably in recent years, and more attention has been paid to improving its production parameters and quality
The movement of craft beers has brought a profusion of raw materials, yeasts and processes that make this drink have a multitude of types, flavors and aromas, which awaken the creativity in its production and the pairing with different foods. In addition to the relaxed bar tables, it incorporates the exchange of information, recipes, products generated and fraternization, even at the time of its elaboration. If before the predominance of a certain type of beer limited its appreciation, after this movement, it becomes the most diversified drink, incorporating ingredients, culture and local patterns into the desired product. This chapter aims to provide a general overview of craft beer making. Some of the ingredients that can be used, and alternatives to traditional ones, as well as an explanation of homemade and artisanal processes, hopping methods, unconventional yeasts and beers will be cited. In the end, a small view of sensory analysis techniques and beer pairing. A good read and beer to all!!!
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.
Please use this link for free access to my PhD dissertation: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/kk91fr75p
Consequences of the Applied Dosing Method.
This supplement to the publication “Revival of a Process (Dry Hopping – Basics and Techniques)” deals with the presentation of various parameters of cold hopping, also referred to as dry hopping. These include dosing quantities, temperature, dosage method, and contact times, all as tested on laboratory and pilot plant scale.
Breweries across the country are investing in energy efficient and low-carbon brewing practices. Drawing insights from the sustainable consumption and ecological economics literature, this analysis evaluates whether consumers are willing to pay more for sustainable beer and what predicts the value of the premium. Based on a survey of beer consumers from across the U.S. that contained one of two willingness-to-pay exercises, we evaluate what respondent attributes are associated with a higher willingness-to-pay for sustainably brewed beer. We find that the majority of beer consumers are willing to pay more for sustainable beer. Consumers who are prepared to pay a premium tend to already pay more per unit of beer, are more aware of their purchasing behavior and the manner in which their consumption patterns may affect the environment, and pursue lifestyles based on professional advancement, helping the environment, and helping other causes.
In the United States, the average usage of aroma hops by brewers has been increasing over the 20th century. This has led to the increased acreage and production of aroma hops. Harvest maturity is one of the main quality drivers of a hop’s aroma potential in beer, however a major pinch-point in commercial hop-harvesting/processing is kilning. This can prevent hops from being picked at optimal timeframes. In the U.S. hops are typically dried to ~8% moisture content in large 26 or 32 in single tier hop beds with dry upward flows of heated air ranging from 130-150ᵒF. In terms of the impact of kiln parameters on hop quality, with the exception of a few studies, most of the data collected has only considered the impact of kiln parameters on alpha concentration. The goal of this study was to evaluate the impact of kiln temperature on aroma quality and dry-hop aroma potential. A pilot kiln was used to dry hops in 10 in beds (Amarillo, picked on the same day and from the same plot) at three kiln temperatures (116ᵒF, 150ᵒF, 170ᵒF). Interestingly, although the hop storage index increased with kiln temperature, the alpha acid concentration was not significantly different between the treatments. The total essential oil content of the 150ᵒF and 170ᵒF treatments were significantly higher than the 116ᵒF treatment. In terms of aroma potential in beer, it was observed that 116ᵒF and 170ᵒF treatments attributed similar aroma intensities and qualities during dry-hopping (both more intense than the 150ᵒF treatment). Although, from a production standpoint drying at 116ᵒF took 5x longer to dry the hops to 8% MC. The enzymatic power of hops also influences beer dextrin profiles and this is a major quality consideration during dry-hopping. Therefore, the impact of kiln temperature on this effect was also evaluated. It was determined that kilning at 170ᵒF roughly halved the enzymatic potential of hops. The results of this study will be used to guide commercial kiln trials and suggest that higher temperatures in the kiln can produce hops with similar aroma potential to hops kilned at lower temperatures and potentially yield shorter drying times.
American craft beer style and flavor is often driven by the unique qualities of American hops. Cascade, Chinook, and Centennial hops are used prominently for dry-hopping singly and/or in blends to impart an intense hoppy aroma to beer. A sensory directed dry-hopping mixture study was performed to understand the contribution that each of these hops make to beer aroma. Utilizing a 4th degree simplex-lattice mixture-design, sixteen beers were prepared (including an "unhopped" control) by dry-hopping a common "unhopped" base beer with different blends of ground whole cone hops made from the three hop cultivars. The treatments were evaluated by trained panelists using descriptive analysis, where the response variables used by the panel encompassed the sensory attributes that described the unique aromatic features of these three hops, (i.e., citrus, tropical/fruity, tropical/catty, and herbal). Using these outputs, the sensory contributions of each individual cultivar, as well as mixtures of the cultivars, were examined on a per attribute basis. These results can be used to select combinations or blends of the three hops for use during dry-hopping that provide similar or dissimilar overall aroma intensity and quality in dry-hopped beer.
Cascade, Chinook, and Centennial hops are used extensively throughout the brewing industry either individually or in various combinations to add hoppy aroma to beer. This high use of hops, particularly via late- or dry-hopping, creates a need to better understand the chemical contribution of these hop varieties during dry-hopping beer in order to predict brewing performance. Solvent-Assisted Flavor Evaporation (SAFE) and Aroma Extract Dilution Analysis (AEDA) was performed on unhopped beer that was dry-hopped individually with each of these varieties as well as the unhopped base. This technique was used to determine the aroma compounds that were the greatest contributors to the dry-hop character of these hops. The analysis of beer prepared with Cascade, Chinook, and Centennial identified 9, 10, and 11 character impact compounds, respectively. Commonalities were observed among the three varieties regarding 2-furanmethanol, linalool, geraniol, cis-geranic acid methyl ester, and n-decanoic acid in dry-hopped beer. Variation between the hop volatiles found to be important for Centennial and Chinook dry-hop aroma was a function of only a few character impact compounds, whereas Cascade was slightly different, anchored heavily by benzenacetaldeyde. The relative similarities and differences that these three hop cultivars attribute to beer during dry-hopping were revealed by comparing which compounds were important for the characteristic aroma profiles of these cultivars in single dry-hop beers.. This knowledge is important for brewers wishing to introduce potential replacement hops and/or reductions for these hop cultivars in the future and guide the direction of future blending studies.
Dry‐hopping is a technique that has been used by brewers to increase the hop aroma and flavour of beer for centuries. Throughout the twenty first century, dry‐hopping has become an increasingly popular method among craft brewers to impart intense hoppy aroma and flavour to beer. Many US craft brewers use extremely high dry‐hop dosing rates of up to 2200 g/hL and this is both unsustainable and potentially wasteful. This study examines the impact of dry‐hopping rate on the sensorial and analytical characteristics of dry‐hopped beers. An unhopped pale beer was statically dry‐hopped with whole cone Cascade from the 2015 harvest over a broad range of dry‐hopping rates (200–1600 g/hL) in replicated, pilot scale (80 L) aliquots. Trained panellists using descriptive analysis scaled the overall and qualitative hop aroma intensity of these beers, as well as the unhopped base beer. Instrumental analysis was used to measure the levels of hop volatile and non‐volatile extraction between the treatments. The relationship between dry‐hopping rate and the sensorial and analytical characteristics of the finished beer was not linear and, based on the extraction efficiencies of select hop volatiles, had an ideal range between 400 and 800 g/hL. © 2018 The Institute of Brewing & Distilling
J. Am. Soc. Brew. Chem. 72(4):231-238, 2014 Considerable expertise is required to grow high-quality hops, and brewers and hop growers alike have a common goal of obtaining the highest quality hops possible. Changes in the chemical composition of hops during plant maturation is a dynamic process requiring a comprehensive chemical and sensory analysis in order to maximize the characteristics of interest to brewers. The effect of harvest date, location, and cultivar on key chemical components of Willamette and Cascade hops was investigated for the 2010 and 2011 growing seasons. Hops were harvested at three time points (early, typical, and late) within a 3 week interval from two different farms in the Willamette Valley, Oregon. A split-plot experimental design for each cultivar was used; each farm represented a main plot and harvest years were designated as subplots. American Society of Brewing Chemists standard methods of analysis were used to measure moisture content, hop acids and their homologs, hop storage index, total essential oil content, and volatile profile by GC-FID. Additionally, difference testing, descriptive analysis, and consumer acceptance testing was conducted using beers brewed with either typical or late harvested Cascade hops from the 2010 harvest year. The response of analytes was dependent on the cultivar being examined, its location within the Willamette Valley, as well as timing of harvest. Hop acids did not change appreciably during plant maturation for the period examined, while hop oil content increased. Increases in oil quantity were strongly correlated (r > 0.90) with increases in α-pinene, β-pinene, myrcene, limo-nene, methyl heptanoate, and linalool concentrations. Clear sensory differences were found between beers brewed with typical and late harvested Cascade hops using triangle testing, consumer preference testing, and descriptive analysis. RESUMEN Se requiere una experiencia considerable para crecer lúpulo de alta calidad, y los cerveceros y productores de lúpulo por igual tienen un objetivo común de obtener la más alta calidad posible de lúpulo. Los cambios en la composición química de lúpulo durante la maduración de las plantas es un proceso dinámico que requiere una sustancia química general y un análisis sensorial con el fin de maximizar las características de interés para los cerveceros. El efecto de la fecha de cosecha, la ubica-ción y la variedad de componentes químicos fundamentales de lúpulo de tipo Willamette y Cascade fue investigado por las temporadas de cultivo 2010 y 2011. El lúpulo se recogieron en tres momentos (principios, típi-cos, y tardías) dentro de un intervalo de 3 semanas a partir de dos granjas diferentes en el Valle de Willamette, Oregon. Se utilizó un diseño experimental de parcelas divididas para cada cultivar; cada finca representaba una parcela principal y año de cosecha fueron designados como subparce-las. Los métodos del ASBC normalizados de análisis se utiliza para medir el contenido de humedad, ácidos de lúpulo y sus homólogos, índice de almacenamiento del lúpulo, contenido total de aceite esencial, y el perfil de volátiles por GC-FID. Además, las pruebas de diferencia, el análisis descriptivo, y las pruebas de aceptación de los consumidores se llevó a cabo utilizando las cervezas elaboradas con cualquiera cosecha típico o tardía de lúpulo de tipo Cascade desde el año de cosecha 2010. La res-puesta de analitos depende de la variedad que se examina, su ubicación dentro del Valle de Willamette, así como el tiempo de la cosecha. Los ácidos de lúpulo no cambiaron apreciablemente durante la maduración de la planta durante el período examinado, mientras que el contenido de aceite de lúpulo aumentó. Los aumentos en la cantidad de aceite fueron fuertemente correlacionados (r > 0.90) con aumentos de concentraciones en α-pineno, β-pineno, mirceno, limoneno, heptanoato de metilo, y lina-lol. Se encontraron diferencias sensoriales claras entre las cervezas elabo-radas con cosechas típico y tardía de lúpulo de tipo Cascade utilizando pruebas triángulo, prueba la preferencia del consumidor, y el análisis descriptivo.
Considerable expertise is required to grow high-quality hops, and brewers and hop growers alike have a common goal of obtaining the highest quality hops possible. Changes in the chemical composition of hops during plant maturation is a dynamic process requiring a comprehensive chemical and sensory analysis in order to maximize the characteristics of interest to brewers. The effect of harvest date, location, and cultivar on key chemical components of Willamette and Cascade hops was investigated for the 2010 and 2011 growing seasons. Hops were harvested at three time points (early, typical, and late) within a 3 week interval from two different farms in the Willamette Valley, Oregon. A split-plot experimental design for each cultivar was used; each farm represented a main plot and harvest years were designated as subplots. American Society of Brewing Chemists standard methods of analysis were used to measure moisture content, hop acids and their homologs, hop storage index, total essential oil content, and volatile profile by GCFID. Additionally, difference testing, descriptive analysis, and consumer acceptance testing was conducted using beers brewed with either typical or late harvested Cascade hops from the 2010 harvest year. The response of analytes was dependent on the cultivar being examined, its location within the Willamette Valley, as well as timing of harvest. Hop acids did not change appreciably during plant maturation for the period examined, while hop oil content increased. Increases in oil quantity were strongly correlated (r > 0.90) with increases in á-pinene, â-pinene, myrcene, limonene, methyl heptanoate, and linalool concentrations. Clear sensory differences were found between beers brewed with typical and late harvested Cascade hops using triangle testing, consumer preference testing, and descriptive analysis.
Dry hopping had more or less become a thing of the past in Germany, but US craft brewers have given this process a new lease of life. About 20 to 25 years ago, American craft brewers started brewing beers which differed considerably from mainstream commercial beers both in terms of bitterness and hop aroma. The existence of more than 1800 craft breweries is clear evidence of the huge success of an industry which continues to grow steadily, as demonstrated by plans for the construction of a further 750 brewing plants [1].
Dry hopping is becoming increasingly popular especially in small breweries. It is a complex and sophisticated method, but it is exactly those qualities which make it a highly efficient method for craft brewers to stand out among the mass of other beers. Empirical experience is the key factor here in the choice of hops and type of application. There is still little known about the transfer rates of hop substances during dry hopping which can provide a great variability of application. A test was made in which four dry hopped pale lager beers were contrasted with a similar produced beer without dry hopping. Here the new German varieties Mandarina Bavaria, Hüll Melon, Hallertauer Blanc and Polaris were used for dry hopping. The dosed quantity of 1.5 ml/hl was based on the hop oil content. The transfer rates were calculated from the difference between analysis values of the dry hopped beers and the control beer divided by the dosed dry hopping quantities. As the calculations were made from three analytical values they inevitably produced relatively large ranges of fluctuation. Of the dosed α-acids, 4 to 5 % can be found in the beers, of the total polyphenols 50 to 60 % and of the low-molecular polyphenols 60 to 70 %. The transfer rates of individual polyphenols show systematic differences; there is no recognizable dependence on variety. The behaviour of the aroma components examined is also not uniform. Terpene hydrocarbons show low yields of about 3 %; linalool transfers to about 100 %. Geraniol seems to react variety-specific with two yields of approx. 50 % and two significantly over 100 %. There is also a variety-specific phenomenon with 2-and 3-methylbutyl-2-propanoate. Chemical transformations with or without yeast enzymes are probably the cause. The results show just how much more work has to be done. The reductions in and transformations of hop aroma substances during ageing of beers are an indication that intensity and type of aroma are subject to changes. The five beers were tasted by a consumer panel of 30. The dry hopped beers had a very intense hop aroma and also a surprisingly intense body. The quality of the hop aroma prevailed over personal preferences and the quality of bitterness was appraised the same. Descriptors: dry hopping, transfer rates, hop aroma compounds, polyphenols
Being one of the most consumed beverages in the world, much effort has been made to reveal the structures responsible for the sensorial characteristics of beer. Yet, the knowledge on the precise contribution of hop-derived volatiles towards the hoppy aroma of beer is rather fragmented. For a long time, the aroma of fresh beer was believed to be mainly imparted by single compounds. However, increasing evidence showed that sensorial perception of the hoppy aroma of beer is more complex than originally assumed. Moreover, the factors responsible for the perceivable differences originating from distinct hop varieties used for late and dry hopping have not been fully revealed. In order to understand how the choice of the hop variety affects the final aroma of beer, we investigated in a previous study with four different hop varieties how the analytical composition of the volatile fraction changes throughout the brewing process and how that affects the composition of late and dry hopped beers. However, the analysis of four different hop varieties arose more questions. Therefore, in this study, we studied 15 other hop varieties during different stages along the brewing process of single hopped beers and analyzed wort and beer samples via headspace solid-phase micro extraction and gas chromatography-mass spectrometry (HS-SPME GC-MS). Additionally, the profiles of the corresponding hop varieties were determined. This enabled the accurate determination of both the full spectrum of hop oil-derived compounds as well as of the higher esters and higher alcohols produced during fermentation. Our investigation reveals substantial changes in the volatile patterns of the wort and beer samples, in comparison with the selected hop variety, which arose from the boiling and fermentation processes, as well as the applied late and additional dry hopping techniques. Concentrations of the floral (e.g. oxygenated fraction of total hop essential oil composed of monoterpene alcohols, esters, ketones and aldehydes) and the sesquiterpenoid hop oil fractions changed significantly along the brewing process. As expected, concentrations of saturated esters and higher alcohols in beers were shown to be mainly influenced by the fermentation and not by the hop variety. Although the concentrations of practically all other compound classes (especially of linalool and geraniol as the most important monoterpene alcohols) were higher in the dry hopped beers, dry hopping does not affect the original intrinsic qualitative composition of hop oil constituents. Yet, substantial quantitative changes were observed. Furthermore, special attention was paid to the influence of additional dry hopping on the transfer behavior of selected hop derived-monoterpene alcohols. Transfer rates for linalool were comparable for all 15 hop varieties, whereas the transfer rates for geraniol differed significantly which indicates that the selected hop variety is of major importance.
http://www.brewingscience.de/index.php?tpl=table_of_contents&year=2015&edition=0001%2F0002&article=85935
Purpose
This paper aims to consider the price premium that consumers state they are willing to pay for products with reused or recycled content. It also aims to address the effect of the impact of product category on consumers' willingness to pay premium prices.
Design/approach/methodology
Willingness to pay was studied for seven different product categories ( n =49).
Findings
Perceived functional risk is an important determinant of the price that consumers are willing to pay for products that have recycled or reused content. It was also found that consumers will switch from a recycled product to a new product within a smaller range of price for products with high functional risk.
Research limitations/implications
The study is exploratory, while it serves its purpose by raising initial questions and finding that this is a complex area that is worth studying. Additional work is clearly required to consider the wide range of potentially relevant variables and a sampling plan that ensures an understanding of the generalisability of findings across the population within a region and across regions.
Practical implications
A technique for understanding consumer willingness‐to‐pay (WTP) is provided and insights into differences are offered between products in terms of WTP for greener products. Practitioners can use this technique to determine the price range and indirectly the profitability of a version of their product based on recycled or reused content.
Originality/value
An understanding of WTP for products with recycled or reused content is developed. This is important as legislation in many countries aims at diverting disposed product from waste dumps to consumers.
Beer brewing is an intricate process encompassing mixing and further elaboration of four essential raw materials, including barley malt, brewing water, hops and yeast. Particularly hops determine to a great extent typical beer qualities such as bitter taste, hoppy flavour, and foam stability. Conversely, hop-derived bitter acids account for an offending lightstruck flavour, which is formed on exposure of beer to light. These various processes are presented in detail, while due emphasis is placed on state-of-the-art hop technology, which provides brewers with efficient means to control bitterness, foam, and light-stability thereby allowing for the production of beers with consistent quality.
Hop aroma components, which mainly comprise terpenoids, contribute to the character of beers. However, pretreatments are necessary before analyzing these components because of their trace levels and complicated matrixes. Here, the stir bar-sorptive extraction (SBSE) method was used to detect and quantify many terpenoids simultaneously from small samples. This simple technique showed low coefficients of variation, high accuracy, and low detection limits. An investigation of the behavior of terpenoids identified two distinct patterns of decreasing concentration during wort boiling. The first, which was seen in myrcene and linalool, involved a rapid decrease that was best fitted by a quadratic curve. The second, which was observed in beta-eudesmol, humulene, humulene epoxide I, beta-farnesene, caryophyllene, and geraniol, involved a gentle linear decrease. Conversely, the concentration of beta-damascenone increased after boiling. As the aroma composition depended on the hop variety, we also examined the relationship between terpenoid content and sensory analysis in beer.
Odorants comprising the hop aromas of beers were examined. Strongly hopped beers with Saazer, Hersbrucker, and Cascade hops were compared with unhopped beer by gas chromatography-olfactometry (CharmAnalysis) and sensory evaluation. Twenty-seven odorants were revealed as hop-derived, which derived either directly from hops or via metabolization, and 19 components were identified. Of the components, linalool, geraniol, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, and ethyl 2-methylpropanoate were determined as odor-active components from their Charm values and aroma values. The muscat-like aroma of Cascade beer and the spicy aroma of Hersbrucker beer were predominant in sensory evaluation, and the contributors to these characteristics were investigated.
In this article, a detailed study on hop alpha-acid isomerization kinetics is presented. Because of the complex wort matrix and interfering interactions occurring during real wort boiling (i.e., trub formation and alpha-acids/iso-alpha-acids complexation), this investigation on alpha-acid isomerization kinetics was performed in aqueous buffer solution as a function of time (0-90 min) and heating temperature (80-100 degrees C). Rate constants and activation energies for the formation of individual iso-alpha-acids were determined. It was found that iso-alpha-acid formation follows first-order kinetics and Arrhenius behavior. Differences in activation energies for the formation of trans- and cis-isomers were noticed, the activation energy for the formation of trans-iso-alpha-acids being approximately 9 kJmol (-1) lower.
Dry hopping is a powerful practice for imparting a multitude of flavors into beer. In this study, the influence of ethanol content, temperature, dosage, and hop variety on the transfer of essential oil during dry hopping was examined on a laboratory scale. The dry hopping was performed with nonalcoholic beer and beer containing 5.0 and 8.1% ethanol at 1 and 20°C using the hop varieties Tettnanger, Cascade, Hallertau Blanc, and Eureka. The results showed that the basic beer, hop variety, and dry hopping regime influence the composition of hop essential oil constituents in dry-hopped beer. The increase of the basic beer ethanol content, and especially the rise in temperature, led to a significant increase in the proportion of monoterpenes such as β-myrcene among hop volatiles in dry-hopped beers. Increasing hop dosage led to higher proportions of alcoholic compounds (linalool). Furthermore, the transfer rates of particular volatile hop-derived substances correlated with their octanol-water partition coefficients (log KOW), which is a measure of the hydrophobicity of a compound, regardless of tested factors in dry hopping. Therefore, it is proposed that the log KOW could be a useful model for the prediction of transfer rates of hop oil flavor components in dry hopping. However, the transfer rates of the alcohols linalool, geraniol, α-terpineol, and 1-octen-3-ol were higher than the expected levels from the log KOW values. These compounds are reported present in bound form in hops and released during dry hopping.
Hops are the most complex and costly raw material used in brewing. Their chemical composition depends on genetically controlled factors that essentially distinguish hop varieties and is influenced by environmental factors and post-harvest processing. The volatile fingerprint of hopped beer relates to the quantity and quality of the hop dosage and timing of hop addition, as well as the overall brewing technology applied. Analytically, the aroma of hops and the flavor of hoppy beers cannot be measured by quantification of a single odorant; moreover, the selection of several key compounds or a comprehensive characterization (profiling) seems reasonable. Analysis of hops and beer is challenging. The selective enrichment of volatiles from complex matrices, separation, unambiguous identification, and precise quantification are the keywords used in this context. This review outlines the synthesis of relevant hop aroma compounds within the plant. The process that incorporates hops into the final beer is described using the hopping techniques used in the industry. Due to the complexity and multiplicity of chemical compounds found in hops, an attempt was made to simplify the information presented by separating the chemical compounds considered into two broad groups: terpenoids and nonterpenoids. This review summarizes approaches commonly used for analysis of hop aroma compounds in hops and beer.
The impact on analytical and sensory bitterness of hop acids and hop-derived polyphenols resulting from dry-hopping in beer was investigated using a pilot-scale dry-hopping study and a commercial dry-hop survey. The pilot-scale dry-hopping study utilized a trained sensory panel to quantify increases in bitterness caused by dry-hopping an unhopped ale at different dosing rates (0–16 g/L) and exposure times (0–72 h). The International Bitterness Unit (IBU) and a range of hop acids and polyphenols were measured in the dry-hopped beer to determine which specific bitter hop components may have been responsible for dry-hopping bitterness. The commercial survey examined the bitter acids and polyphenol chemistry of 15 different commercial beers, pre- and post-dry-hopped, brewed by Pacific Northwest breweries. Although iso-a-acids (IAA) were the main contributor to beer bitterness, humulinones (oxidized a-acids) and polyphenols were also potentially significant contributors to bitterness, particularly in heavily dry-hopped beer. The increase in beer bitterness (IBU) as a result of dry-hopping was attributed to humulinone extraction and, in some cases, polyphenol extraction. The commercial survey noted a decrease in the total IAA concentrations as a result of dry-hopping in a majority of the samples tested, indicating that the dry-hopping process may remove IAA from beer.
Over the last century, the brewer's archetype of hop chemistry, hopping technology, hop utilization, and hop flavor has substantially transformed. During the 1950s Miller Brewing Company began pioneering work to unravel some of the mysteries of hop chemistry. This work, combined with research findings from various other groups throughout the world, revolutionized the industry. Such realizations of hop chemistry and hop technology in addition to the widening array and understanding of aromatic hop varieties allow the modern practical brewer a diverse palette of hopping choices to ensure production of highly consistent, flavorful, quality beers. Today, brewers may artfully and innovatively craft beers with enhanced properties such as light stability, increased foamability/head retention, enriched hop flavors, optimized beer mouthfeel, increased hop utilization, and improved microbial and flavor stability. This paper guides the reader through a history of hop chemistry, revealing the "bitter, twisted truth of the hop" from the discovery of hop acids and their transformations to the many innovations that led to the development of advanced hops and novel hop products necessary for the successful development of new and novel beer brands of consistent quality in a large brewery scenario. This paper also provides a framework from which the smaller, craft brewer can take advantage of the more recent developments in hop chemistry to gain enhanced quality, consistency, economy, and novelty moving forward.
Terpenes and terpenoids belong to the largest and most diverse class of natural products. Due to the increasing importance of their applications and the emerging perception of their impact on the environment, the available physico-chemical characterization is insufficient. In this work the water solubility of geraniol, linalool, dl-citronellol, thymol, eugenol, carvacrol and p-cymene, in the temperature range from (298.15 to 323.15) K, and at atmospheric pressure, is studied. Due to the low solubility of these compounds a novel technique was adopted for their measurements and validated using the aqueous solubility data for sparingly soluble aromatic compounds. The thermodynamic properties of solution were derived from the experimental data at infinite dilution. It is shown that the solubility of terpenes in water is an endothermic process confirming the existence of UCST phase diagrams, and only for carvacrol and eugenol is entropically driven. The experimental information is shown in a two-dimensional chemical space diagram providing indications to their probable distribution in the environment once released.
When hops are added to beer, varying degrees of hoppy aroma persist as a result of cultivar differences and the point of hop addition. Dry hopping is a technique whereby hops are added to beer to leverage the maximum aroma potential of the hop oil. Given that hop oil serves as the primary reservoir of aromatic compounds in the hops, we hypothesized that using hops with greater total oil content (mL/100 g) will result in higher levels of hoppiness for dry-hopped beers. An unhopped beer was dry hopped with 23 individual Cascade hop lots, and the resultant beer was evaluated with sensory descriptive analysis. The results demonstrated a negligible role of total oil content (mL/100 g) as an indicator of hoppiness. In fact, there was no correlation between total oil content and overall hop aroma intensity. Therefore, the specific volume of hop oil is an inadequate indicator of hoppiness potential in the dry-hop system. This work challenges several conventional ideas, namely, that using hops with higher oil content for dry hopping promotes a greater degree of hoppy aroma in beer. This research affirms the complexity of how hop materials relate to sensory aroma performance in beer systems.
Various factors were examined to determine their impact on the rate of isomerization of α-acids (humulones) to iso-α-acids (isohumulones) during kettle boiling. A model wort boiling system was used that employed multiple 12-mL stainless steel vessels to heat samples (α-acids in an aqueous, pH-buffered solution with other compounds included as specified) at 100°C for 140 min. Concentrations of humulones and isohumulones were quantified at discrete time points using HPLC. Of the factors tested (glucose, maltose, calcium, and pH ranging from 4.8 to 6.0), none were shown to affect the rate of production of iso-α-acids. While pH had a marked effect on the concentrations of α-acids as measured, the differences may be attributed to solubility issues (since the solubility limit was approached and exceeded) that did not appear to affect the rate of iso-α-acid production.
Intensive water and energy use, copious volumes of wastewater and solid waste, and large carbon footprints make the process of brewing and distributing beer a not-so-(environmentally)-friendly industry. However, the rise of craft breweries and their perceived foci on environmental, economic and/or social sustainability trends have promulgated a greening in the beer industry at local to global scales. To assess the geographies of sustainability in the craft beer industry, we distributed a mixed method survey to all regional craft breweries in the United States. Overall, more sustainable practices have been adopted at various levels of the craft beer production, including the reduction of water and energy use and increased energy efficiency, the use of organic or local ingredients, and the incorporation of a culture that promotes sustainability. These and related findings showcase certain sustainability trends and practices being adopted by regional craft breweries in the United States. © 2014 Springer Science+Business Media Dordrecht. All rights are reserved.
Beer brewing is an intricate process encompassing mixing and further elaboration of four essential raw materials, including barley malt, brewing water, hops and yeast. Particularly hops determine to a great extent typical beer qualities such as bitter taste, hoppy flavour, and foam stability. Conversely, hop-derived bitter acids account for an offending lightstruck flavour, which is formed on exposure of beer to light. These various processes are presented in detail, while due emphasis is placed on state-of-the-art hop technology, which provides brewers with efficient means to control bitterness, foam, and light-stability thereby allowing for the production of beers with consistent quality.
Several hundred aroma compounds are known in hops but only a few have great impact to hop aroma of beer. Adding hops at late stages of boiling gives a pleasant hoppy flavour to the final beer. Linalool is known to be a good indicator for such a hoppy flavour. In this study it could be shown that different hop varieties have different transfer rates of linalool and other aroma compounds. The behaviour of the aroma compounds is different and compound specific. Linalool increases during fermentation and there were differences between beers fermented at 8 °C and 12 °C. The 12 °C samples showed lower concentrations of linalool but higher scores in aroma intensity. Possible explanation are additive interactions between fermentation-by-products and hop aroma compounds.
Brewing is one of the oldest and most complex technologies in food and beverage processing. Its success depends on blending a sound understanding of the science involved with an equally clear grasp of the practicalities of production. Brewing: science and practice provides a comprehensive and authoritative guide to both of these aspects of the subject. After an initial overview of the brewing process, malts, adjuncts and enzymes are reviewed. A chapter is then devoted to water, effluents and wastes. There follows a group of chapters on the science and technology of mashing, including grist preparation. The next two chapters discuss hops, and are followed by chapters on wort boiling, clarification and aeration. Three chapters are devoted to the important topics of yeast biology, metabolism and growth. Fermentation, fermentation technologies and beer maturation are then reviewed, followed by a consideration of native African beers. After a discussion of brewhouses, the authors consider a number of safety and quality issues, including beer microbiology and the chemical and physical properties of beer, which contribute to qualities such as flavour. A final group of chapters cover packaging, storage, distribution and the retail handling of beer. Based on the authorsâ? unrivalled experience in the field, Brewing: science and practice is a standard work for the industry. © 2004 Dennis E. Briggs, Chris A. Boulton, Peter A. Brookes and Roger Stevens. All rights reserved.
The brewing industry is one of the largest industrial users of water. In spite of significant technological improvements over the last 20 years, energy consumption, water consumption, wastewater, solid waste and by-products and emissions to air remain major environmental challenges in the brewing industry. This article reviews some of these challenges with a focus on key issues: water consumption and waste generation, energy efficiency, emission management, environmental impact of brewing process and best environmental management practices which do not compromise quality of beer. The review is meant to create an awareness of the impact of beer production on the environment and of, practices to reduce environmental impact.
The hop cones of the female plant of the common hop species Humulus lupulus L. are grown almost exclusively for the brewing industry. Only the cones of the female plants are able to secrete the fine yellow resinous powder (i.e. lupulin glands). It is in these lupulin glands that the main brewing principles of hops, the resins and essential oils, are synthesized and accumulated. Hops are of interest to the brewer since they impart the typical bitter taste and aroma to beer and are responsible for the perceived hop character. In addition to the comfortable bitterness and the refreshing hoppy aroma delivered by hops, the hop acids also contribute to the overall microbial stability of beer. Another benefit of the hop resins is that they help enhance and stabilize beer foam and promote foam lacing. In an attempt to understand these contributions, the very complex nature of the chemical composition of hops is reviewed. First, a general overview of the hop chemistry and nomenclature is presented. Then, the different hop resins found in the lupulin glands of the hop cones are discussed in detail. The major hop bitter acids (- and β-acids) and the latest findings on the absolute configuration of the cis and trans iso--acids are discussed. Special attention is given to the hard resins; the known δ-resin is reviewed and the ε-resin is introduced. Recent data on the bittering potential and the antimicrobial properties of both hard resin fractions are disclosed. Attention is also given to the numerous essential oil constituents as well as their contributions to beer aroma. In addition to the aroma contribution of the well-known essential oil compounds, a number of recently identified sulfur compounds and their impact on beer aroma are reviewed. The hop polyphenols and their potential health benefits are also addressed. Subsequently, the importance of hops in brewing is examined and the contributions of hops to beer quality are explained. Finally, the beer and hop market of the last century, as well as the new trends in brewing, are discussed in detail. Hop research is an ever growing field of central importance to the brewing industry, even in areas that are not traditionally associated with hops and brewing. This article attempts to give a general overview of the different areas of hop research while assessing the latest advances in hop science and their impact on brewing. Copyright © 2014 The Institute of Brewing & Distilling
Although hop technology has been a substantial part of brewing science for the last 130 years, we are still far from claiming to know everything about hops. As hops are considered primarily as a flavour ingredient for beer, with the added benefit of having anti-microbial effects, hop research is focused on hops as a bittering agent, as an aroma contributor and as a preservative. Newer fields in hop research are directed toward the relevance of hops in flavour stability, brewing process utilisation, the technological benefits of hops in brewing as well as hops as a source of various substances with many health benefits. However the more we find out about the so-called “spirit of beer” the more questions emerge that demand answers. While hop research was only an ancillary research field for decades, during the last ten years more universities and breweries have determined that hops must play a meaningful role in their research efforts. This article gives an overview of the up-to-date knowledge on hop aroma, hop derived bitterness, and the role of hops in flavour stability as well as light stability. Hop research is a wide field, therefore in this review only selected topics are reviewed. Other research areas such as hops utilisation, the antifoam potential of hops, or the advances in knowledge pertaining to the physiological valuable substances of hops go beyond the scope of this article.
Trials have been completed on 1959 and 1960 crop Fuggles, with drying at three temperatures (140, 150 and 160° F.). Examination by the Borough indicated small differences in appearance, rub and aroma. Hops dried at the lower drying temperatures were assessed more highly. With the 1959 crop, these differences did not alter the valuation; with the 1960 crop, hops dried at the higher temperatures were marked down. Hops dried at the lower temperatures had the highest α acid content. Differences observed in the brewing results or in the flavour of the resulting beer could not be associated with the drying temperature.
Prior generalizations about the ecological roles of monoterpenes may be misleading if based on the presumed insolubility of monoterpenes in water. We determined the aqueous solubility of 31 biologically active monoterpenes by gas chromatography. While hydrocarbons were of low solubility (< 35 ppm), oxygenated monoterpenes exhibited solubilities one or two orders of magnitude higher, with ranges of 155-6990 ppm for ketones and of 183-1360 ppm for alcohols. Many monoterpenes are phytotoxic in concentrations under 100 ppm, well below the saturated aqueous concentrations of oxygenated monoterpenes. Therefore, even dilute, unsaturated solutions of monoterpenes, occurring naturally in plant tissues and soil solutions, may act as potent biological inhibitors.
Controlled degradation of myrcene, the major monoterpene hydrocarbon of hop oil, is discussed with special emphasis on the roie of myrcene as a precursor for the formation of flavor compounds occurring in naturally aging hop oil. Products are isolated and identified by means of gas chroma-tographic, mass spectral, and infrared analyses. Related possible degradation pathways are suggested for a number of these second- and third-order terpenoid constituents, and spectral data for several terpene alcohols, oxides, ketones, and polymerization products are reported.
Multicomponent liquid−liquid equilibria measured at T = 298.15 K have been reported for the ternary (water + methanol + α-pinene or + β-pinene or + limonene) and (water or methanol + α-pinene + limonene) systems and the quaternary (water + methanol + α-pinene + limonene) systems. The mutual solubilities of terpenes (α-pinene, β-pinene, and limonene) in methanol and water have been measured at T = 298.15 K. The experimental multicomponent liquid−liquid equilibrium data have been satisfactorily represented by using the extended UNIQUAC and modified UNIQUAC models.
Octanol-water partition coefficients (Kow) for 57 terpenoids were measured using a RP-HPLC method. Sample detection was achieved with standard UV and refractive index detectors and required no special column treatment. Measured log Kow values for the terpenoids ranged from 1.81 to 4.48 with a standard error of between 0.03 and 0.08 over the entire range. Partition coefficients determined by the RP-HPLC method were compared against shake flask, atom/fragment contribution, fragment and atomistic methods. The HPLC values were found to give the best correlation with shake flask results. Log Kow values calculated by the atom/fragment contribution method gave the best correlation with the HPLC values when compared to fragment and atomistic methods.
Application of aroma extract dilution analysis on the volatiles obtained from dried cones of Spalter Select hops grown in the German hop-growing area of Hallertau revealed 23 odorants in the flavor dilution (FD) factor range of 16-4096, 20 of which could be identified. On the basis of high FD factors, trans-4, 5-epoxy-(E)-2-decenal, linalool, and myrcene were identified as the most potent odorants, followed by ethyl 2-methylpropanoate, methyl 2-methylbutanoate, (Z)-1,5-octadien-3-one, nonanal, (E,Z)-1,3, 5-undecatriene, 1,3(E),5(Z),9-undecatetraene, propyl 2-methylbutanoate, 4-ethenyl-2-methoxyphenol, and 1-octen-3-one. Ten of the high-impact hop aroma compounds had previously not been identified as hop constituents and, in particular, 1,3(E),5(Z), 9-undecatetraene has not yet been reported as a food odorant. In an extract obtained from fresh hops, in addition to the odorants found in dry hops, (Z)-3-hexenal was characterized as a further key odorant rendering an additional green aroma note to the fresh material.
The selection and quality of hops is a major determinant in beer flavour. Brewers acknowledge that distinctive characteristics of different hop varieties can be traced to the composition of their essential oils. The difficulty in characterising complex mixtures such as hop oil using 1-D chromatography is that many compounds co-elute. With the introduction of comprehensive multidimensional capillary gas chromatography (GC x GC), there is a tremendous improvement in the separation power or peak capacity. Recent work using GC x GC with flame ionisation detection has suggested that there may be over 1,000 compounds in hop oil. This work describes the use of GC x GC combined with TOFMS detection (Leco Pegasus 4D instrument) to analyse Target hop oil. The TOFMS spectral acquisition rate of 60 Hz provided sufficient spectra per peak (2-D peak base width of 0.1-0.2 s) for identification (119 components were identified with 45 previously unreported compounds). When analysing results, an advantage of GC x GC coupled to TOFMS is that 2-D chromatograms can be viewed for individual masses that are characteristic of particular functional groups. This allows the analyst to view the various homologous series of compounds although in certain cases coelution may still be present as shown by the esters with mass 75.
To model the emission dynamics and changes in fractional composition of monoterpenoids from plant leaves, temperature dependencies of equilibrium coefficients must be known. Henry's law constants (H(pc), Pa m3 mol(-1) and octanol/water partition coefficients (K(OW), mol mol(-1)) were determined for 10 important plant monoterpenes at physiological temperature ranges (25-50 degrees C for H(pc) and 20-50 degrees C for K(OW)). A standard EPICS procedure was established to determine H(pc) and a shake flask method was used for the measurements of K(OW). The enthalpy of volatilization (deltaH(vol)) varied from 18.0 to 44.3 kJ mol(-1) among the monoterpenes, corresponding to a range of temperature-dependent increase in H(pc) between 1.3- and 1.8-fold per 10 degrees C rise in temperature. The enthalpy of water-octanol phase change varied from -11.0 to -23.8 kJ mol(-1), corresponding to a decrease of K(OW) between 1.15- and 1.32-fold per 10 degrees C increase in temperature. Correlations among physico-chemical characteristics of a wide range of monoterpenes were analyzed to seek the ways of derivation of H(pc) and K(OW) values from other monoterpene physico-chemical characteristics. H(pc) was strongly correlated with monoterpene saturated vapor pressure (P(v)), and for lipophilic monoterpenes, deltaH(vol) scaled positively with the enthalpy of vaporization that characterizes the temperature dependence of P(v) Thus, P(v) versus temperature relations may be employed to derive the temperature relations of H(pc) for these monoterpenes. These data collectively indicate that monoterpene differences in H(pc) and K(OW) temperature relations can importantly modify monoterpene emissions from and deposition on plant leaves.
Statistical Report Presented by the Hop Growers of America
- A George
George, A. 2017 Statistical Report Presented by the Hop
Growers of America; 2017.
A study of factors affecting the extraction of flavor when dry hopping beer
- P H Wolfe
Wolfe, P. H. A study of factors affecting the extraction of flavor
when dry hopping beer. Thesis -Master of Science. Oregon
State University, 2012.
The Chemistry of Hop Constituents -Chapter 8 in Brewing Science and Practice
- D E Briggs
- C A Boulton
- P A Brookes
Briggs, D. E.; Boulton, C. A.; Brookes, P. A.; Stevens, R., Eds.
The Chemistry of Hop Constituents -Chapter 8 in Brewing
Science and Practice, Woodhead Publishing: Sawston, 2004;
pp 255-305.
Dry Hopping on a Small Scale: Considerations for Achieving Reproducibility
- D M Vollmer
- T H Shellhammer
Vollmer, D. M.; Shellhammer, T. H. Dry Hopping on a Small
Scale: Considerations for Achieving Reproducibility. Tech. Q.
Master Brew. Ass. Am. 2016, 53, 140-144.
- J P Maye
- R Smith
Maye, J. P.; Smith, R. Hidden Secrets of the New England IPA.
Tech. Q. Master Brew. Ass. Am. 2018, 55, 88-92.
Octanol-Water Partition Coefficient for Organic Compounds -Chapter 16
- C L Yaws
Yaws, C. L. Octanol-Water Partition Coefficient for Organic
Compounds -Chapter 16. In Yaws' Handbook of Properties for
Aqueous Systems. Knovel: Norwich, NY, 2012.
Linalool-A Key Contributor to Hop Aroma. MBAA Global Emerging Issues
- S Hanke
Hanke, S. Linalool-A Key Contributor to Hop Aroma. MBAA
Global Emerging Issues 2009. https://www.mbaa.com/brewresources/Documents/Linalool.pdf
Impact of Kiln Temperatures on the Aroma and Enzymatic Potential of Hops during Dry-Hopping. Recent Advances in Hop Science
- S R Lafontaine
- D G Hauser
- R Foster
- J Donaldson
- D Gamache
- T H Shellhammer
Lafontaine, S. R.; Hauser, D. G.; Foster, R.; Donaldson, J.;
Gamache, D.; Shellhammer, T. H. Impact of Kiln Temperatures
on the Aroma and Enzymatic Potential of Hops during Dry-Hopping. Recent Advances in Hop Science, European Brewing
Congress: N€ urnberg, 2018.