Dry Hop Research Articles

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

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

Hop (Humulus lupulus L.) extract reverts glycaemic imbalance and cognitive impairment in an animal model of obesity.

The rates of overweight and obesity around the world have increased in past years. The body's adipose tissue stimulates the antioxidant and oxidation imbalance capacity at the cellular level. This scenario favors an inflammatory low-grade systemic condition starting with insulin resistance, which in turn may involve diabetes mellitus type 2 and cognitive decline afterward. Neurological diseases have been correlated to senile age diseases over time. This scenario calls for a change in the incidence of obesity in the younger generation. An unhealthy dietary consumption together with sedentary habits might lead to poor gut absorption of nutrients. Several plants and foods have bioactive compounds that can reduce or inhibit radical scavengers, reactive oxygen species, and metal ion complexes that threaten the cerebral defense system. The bitter acids from hops (Humulus lupulus L.) have been demonstrated to have promising effects on lipid and carbohydrate metabolism improvement, reducing inflammatory responses through alpha acids, beta acids, and analogs action. Therefore, the current study aimed to investigate the bioactivity of hop bitter acids in obese and lean mice. For that, a dry hop extract (DHE) was obtained by applying carbon dioxide as the fluid of supercritical extraction. Afterward, seventy-eight male mice of the C57BL/6J strain were weighed and randomly distributed into six groups of 13 animals each according to the diet offered: (NO) normolipidic diet, (NO1) normolipidic diet containing 0.35% alpha acids, (NO2) normolipidic diet containing 3.5% alpha acids, (HP) hyperlipidic diet, (HP1) hyperlipidic diet containing 0.35% alpha acids, and (HP2) hyperlipidic diet containing 3.5% alpha acids. After applying the glycemic tolerance and insulin tolerance tests, a better stabilization of glycemia levels and weight gain among those animals fed with DHE (NO2 and HP2) were observed in comparison to the obese control group (HP) (p < 0.05). There was also an amelioration of antioxidant capacity observed by checking the enzymatic profile by SOD and an apparent mitigation of brain degeneration by checking GSK3β and p-IRS1 proteins expression (p < 0.05). The y-maze cognitive test applied to highlight possible obesity-harmful animal brains did not indicate a statistical difference between the groups. Although the weekly dietary intake between the obese HP2 group (33.32 ± 4.11, p < 0.05) and control HP (42.3 ± 5.88, p < 0.05) was different. The bioactive compounds present in DHE have demonstrated relevant effects on glycemic control, insulin signaling, and the consequent modulatory action of the obesity-related markers with the brain's inflammatory progression.

Variability and stability of essential oil composition in Ukrainian hop varieties

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.

Вплив шишок хмелю і вітаміну E на кетогенез та антиоксидантний статус корів

The purpose of the work was the correction rumen fermentation in the transition cows to prevent metabolic disorders. For the experiment, two groups of Ukrainian dairy black-and-white breed cows were formed, 10 animals per group. The experiment lasted 3 weeks prepartum and 3 weeks postpartum. Animals received a balanced diet, which consisted of haylage, silage, barley, wheat, corn, soybean meal, salt, mineral and vitamin premix. The first group was the control. To the diet of second group 300 mg of α-tocopherol acetate (0.6 g of Rovimix E-50) and 1 g/kg of dry hop cones per kg of dry matter was added. Before calving, the tested feed additive reduced the concentration of peroxide oxidation products in the cows blood (P&lt;0.05) without affecting other parameters. Changes that are more significant detected after calving. A decrease in the concentration of lipid hydroperoxides (P&lt;0.05), TBARS (P&lt;0.05), and beta-hydroxybutyrate (P&lt;0.05) were observed in the blood of the cows of the experimental group. Therefore, the addition into diet of transition cows of α-tocopherol and hop cones inhibits the lipid peroxidation and reduces the ketones formation. So, this feed supplement can be used to prevent ketosis and steatosis in cows.

Impact of Dry Hopping on Beer Flavor Stability.

To investigate the chemical and sensorial impact of dry hopping time on typical pale ale, a standardized beer was produced and separated into ten vessels. Nine vessels were dry hopped, and one vessel remained un-hopped as a control. Impact of dry hopping contact time was investigated over 96 h. Polyphenols and iso-α-acid t/c ratio were analyzed in both Young and Aged beer samples. Total polyphenol content generally increased in both young and aged treatments compared to controls. Analysis of the t/c ratio suggests that both Young and Aged beers were chemically preserved to some degree after approximately 12 h at the given dry hopping rate regardless of age. Within the Aged beer trials, 96 h of dry hop contact yielded a significant increase in t/c ratio compared to all other Aged trials. This suggests that a 4-day dry hop regime may yield additional oxidative protection of iso-α-acids in beers stored unrefrigerated for 30 days. Descriptive analysis was also performed with an 8-person, trained panel; however, beers were sensorially distinguished by their aging time as opposed to their dry hopping time.

Correction the blood biochemical parameters in transition dairy cows by hop cones and vitamin E supplement

In the prevention and treatment of cow ketosis, the regulation of glucose and fatty acids is the main focus, while ammonia intoxication is largely ignored. The intensity of formation of the rumen ammonia can be reduced by ionophore antibiotic monensin. Hop cones contain a number of biologically active components including phytoionoрhores: prenylated polyphenols lupulon, humulon and their derivatives. Therefore, hop cones can be considered as a potential substitute for antibiotics-ionophores. Vitamin E, fed to ruminants in large quantities, stimulates the cellulosolytic bacteria of the rumen. Accordingly, co-feeding cows with hops and vitamin E supplements can reduce ammonia formation without inhibition the carbohydrate fermentation in the rumen. The experiment used two groups of dry Ukrainian dairy black-and-white breed cows with productivity 6–7 thousand kg of milk for previous lactation, 10 animals per each group. The trial was performed during the last 3 weeks of dry period and the first 3 weeks after calving. Animals were fed a standard balanced diet containing: grass silage, corn silage, barley grain, corn grain, soybean meal, molasses, salt, mineral and vitamin premix. The first group was the control. The diet of second group was supplemented with 300 mg of α-tocopherol acetate (0.6 g of Rovimix E-50) and 1g of dry hop cones per kg of DM. Prior to calving, the tested feed additive reduced the concentration of lipid peroxidation products (P &lt; 0.05) in the blood plasma without affection other parameters. More significant changes were detected after calving. An increase in glucose concentration (P &lt; 0.05), triacylglycerol (P &lt; 0.05), cholesterol esters (P &lt; 0.05) and a decrease in the concentration of NEFA (P &lt; 0.05) were found in the blood of cows of the experimental group in a week after parturition. One month after calving, differences between control and experimental blood plasma parameters were significantly less pronounced. Therefore, addition of 300 mg of α-tocopherol acetate and 1 g/kg of dry hop cones per kg of dry matter of the diet during the transition period stimulates liver glucose synthesis and reduces the rate of fatty acid release from adipose tissue. The specified feed additive can be used to prevent metabolic disorders in early-lactation dairy cows.

Effect of deficit irrigation on yield quantity and quality, water productivity and economic returns of four cultivars of hops in the Yakima Valley, Washington State

Hop production, like all other water uses in the area, is facing water availability concerns. Deficit irrigation may address water scarcity issues in hop production. This study quantifies the effect of deficit irrigation on hop yield, quality, water productivity and grower profitability. Mt. Hood, Columbus, Chinook and Willamette cultivars were grown under three irrigation levels; 60, 80 and 100% of the crop’s irrigation requirement, using a sub-surface drip irrigation system. Results show that hop plants generally respond to water stress with yield reductions; compared to the 100% irrigation level, the 60% irrigation level caused reductions in total 2-year dry hop cone yield of 30%, 33%, 25%, and 19% for Mt. Hood, Willamette, Columbus and Chinook cultivars respectively, whereas, the 80% irrigation level caused total 2-year yield reductions of 14%, 10%, and 3% for Mt. Hood, Willamette and Chinook cultivars respectively. For Columbus, the 80% irrigation level gave 2% more dry hop cone 2-year total yield than the fully irrigated treatment. Hop cone quality was however not affected; the concentrations of alpha and beta acids were generally similar across all irrigation levels for cultivars for each year of study. The cost of water in Washington State does not vary with changes in water use; only water pumping costs vary with water use. Pumping costs are only 1.5% of the total cost of producing hops in an established yard. As such, savings in pumping costs due to using less water were minimal when compared to the resulting loss in revenue due to yield reductions. Deficit irrigating hops grown under sub-surface drip irrigation system in the Yakima Valley is therefore not economically viable. However, under conditions of water scarcity, high water prices or when there are more profitable alternative uses for the water, deficit irrigation may then be considered. Deficit irrigation though has potential to improve water productivity as observed from the 2012 results. Under the 60% irrigation level, water productivities were 0.42, 0.55, 1.02, and 0.44kg/m3 for Mt. Hood, Willamette, Columbus, and Chinook respectively. Under the 80% irrigation level, water productivities for Mt. Hood, Willamette, Columbus, and Chinook were 0.34, 0.41, 0.95, and 0.45kg/m3 respectively. For full irrigation, water productivities were 0.33, 0.31, 0.84, and 0.37kg/m3 for Mt. Hood, Willamette, Columbus, and Chinook respectively. This study provides production functions for the hop cultivars for forecasting yield quantities under various irrigation amounts.

Bulk properties of densified hop cones related to storage and throughput measurements

Hop is one of the most important materials for beer production. Nevertheless the material density of hop is little known even though this information is needed for the harvesting, processing and storage of the hop cones. To fill this gap in knowledge, densification experiments were carried out during 2013 harvesting season with wet and dry hop cones of different varieties. It was shown that for hop cones of all varieties in dry state that pressure increased with increasing material density. In a wet state, Sladek and Vital varieties showed different behaviour. Higher initial densities meant greater hardness of those two varieties. The densification process caused significant increase in the densification curve slope at the initial and final points. The initial slope was very high for the Sladek and Vital varieties in a wet state. Resulting pressure values were statistically different for most of the tested varieties. The differences in densification parameters were in all cases transferred from the wet to dry states. Differences found between varieties can significantly influence hop material throughput during harvesting as well as the behaviour of hop cones during post-harvest processing and storage.

FLAVONOLS HPLC ANALYSIS, IN VITRO BIOLOGICAL ACTIVITIES IN SELECTED HUMULUS LUPULUS L. GENOTYPES

Abstract The Humulus lupulus L. is well known as necessary raw material for beer production. The main structural classes of chemical compounds identified from hop cones include terpenes, bitter acids, prenylated chalcones, and flavonol glycosides. They were subjects of presented work. The content of quercetin was found in the range 490 - 1092 μg/g and that of kaempferol from 218 to 568 μg/g of the dry hop cones. The content of isorhamnetin was very low in all varieties. From biological activities in vitro point of view, relative high level of inhibition activity was observed for six hop genotypes - Zlatan, Lučan, and the Oswald's clones 31, 70, 71, 72, 114 on both enzymes thrombin and urokinase, but without correlation to analyzed flavonols content. In spite of this, antioxidant activity, measured by both the BCLM and HPE methods, was found high and seem to be in correlation with content of analyzed flavonols. Particularly the Oswald's clone 114 expressed very potent biological activities. In general, obtained results indicate that hop cones are valuable material also for other application others than beer production.

The Dynamic Of Essential Oil Accumulation In Hop Cones During 2012 Year

Hop cones have lupulin glands which occur on the outer lower surface of the bracteoles and the entire surface of the perianth. The constituents of these glands include bitter acids and essential oil components (Auerbach et.al., 2000). Dry hop contains 0.5-2.0% of essential oil. Hop essential oils consist of a large number of different components and although their composition is influenced by the environment (Ĉerenak et.al., 2011). Aims: This study is a continuation of the research started in 2011 (Salanţă et.al., 2012), where the dynamic of essential oil accumulation in hop cones during 2011 year, were reported. In this paper, samples from 2012 year crop were subjected to hydrodistillation in order to content in essential oils. All reported results will be used in a future research, to determine the gas chromatographic composition of essential oils extracted.

The Effect of Protein and Carbohydrate Levels on the Chemical and Sensory Properties of Beer

The influence of interactions between volatile compounds and different levels of beer carbohydrates and proteins was evaluated. Two beer treatments containing different concentrations of proteins (pro) and carbohydrates (CHO) (low pro/low CHO and high pro/high CHO) and known levels of five volatile compounds (ethanol, myrcene [dry hop], ethyl hexanoate [apple], isoamyl acetate [banana], and benzaldehyde [almond]) were created and evaluated using GC/MS and a trained sensory panel. With the exception of benzaldehyde, the GC/MS analysis showed significantly lower headspace concentrations of the volatile compounds in the high pro/high CHO beer treatment (P ≤ 0.05). Trained sensory panel evaluation results revealed that, in the high pro/high CHO beer treatment, apple and almond aromas were perceived as more intense, along with increases in apple, almond, and dry hop flavors. A significant decrease in the intensity of banana flavor was also observed (P ≤ 0.05). The results highlighted the difference between data collected by instrumental and sensory analysis, suggesting the need for caution when correlating results between the two methods. This study also provided detailed assessment of important flavor component interactions in beer, and contributed to the limited knowledge about the interaction between nonvolatile (carbohydrates and proteins) and volatile components in beer.

Sensory Descriptive Analysis and Free-Choice Profiling of Thirteen Hop Varieties as Whole Cones and After Dry Hopping of Beer

Sensory descriptive analysis and free choice profiling have been applied to the characterization of aroma in thirteen hop varieties, both in the whole cone form and after the hops had been used to dry hop beer. 180 terms were identified and used for the classification of hops. Only two of the varieties displayed closely similar profiles. Varieties could, however, be broadly grouped into those with overriding citrus notes and those with substantial green tea, hay and wet wood nature. Dry hopping tends to compress varieties when evaluated for aroma, perhaps indicating a degree of masking by other beer components. However the aroma notes detected are similar whether assessed in whole cones or in beers.

Sensory Descriptive Analysis and Free-Choice Profiling of Thirteen Hop Varieties as Whole Cones and after Dry Hopping of Beer

Sensory descriptive analysis and free choice profiling have been applied to the characterization of aroma in thirteen hop varieties, both in the whole cone form and after the hops had been used to dry hop beer. 180 terms were identified and used for the classification of hops. Only two of the varieties displayed closely similar profiles. Varieties could, however, be broadly grouped into those with overriding citrus notes and those with substantial green tea, hay and wet wood nature. Dry hopping tends to compress varieties when evaluated for aroma, perhaps indicating a degree of masking by other beer components. However the aroma notes detected are similar whether assessed in whole cones or in beers.

Comparison of Czech hop cultivars based on their contenst of secondary metabolites

Seven Czech hop varieties (dry hop cones) coming from the harvest of 2008 (Agnus, Bor, Harmonie, Premiant, Rub&amp;iacute;n, Sl&amp;aacute;dek, and Saaz) were compared for their composition depending on their varietal differentiation. These cultivars were analysed for the contents of &amp;alpha;- and &amp;beta;-bitter acids analogues, essential oils, and polyphenols. Hop essential oil constituents significantly contribute to the individual hop varieties. The dichotomous key for the authentication of Czech hop varieties was established based on some characteristic varietal markers.

Response of the Czech hybrid hop cultivar Agnus to the term of pruning, depth of pruning and number of trained bines

Agnus is a Czech hybrid hop cultivar and a statistically significant influence of depth and term of pruning on harvested hop cones yield and on alpha-bitter acids content in hop cones were found in this study. Evaluated agrotechnical measures, i.e. depth of pruning, term of pruning and number of trained bines, considerably influenced performance and quality of newly grown hop genotype. Every year, we found a positive influence of shallow pruning on yield (increase of dry hop cones yield in 2003 by 0.37 t/ha, in 2004 by 0.28 t/ha and in 2005 by 0.02 t/ha). The hop yield of plants treated with shallow pruning increased on average by 11.6% in three years. We proved a statistically significant influence of three-bines training system on one hop pole, i.e. 3 + 3 bines from each plant. We found that alpha-bitter acids content corresponds with cones yield and indicates a convenience of shallow pruning. Pruning term influenced alpha-bitter acids yield and dynamics of their formation (in the first pruning term yield it was 155 kg/ha, in the second pruning term it was 169 kg/ha, and in the third pruning term it was 175 kg/ha).

Investigation of carbofuran and its metabolites by gas-liquid chromatography in green and dry hops

Processed hop cones (Humulus americanus) are an important flavoring component in beer, and it is possible that carbofuran and its metabolites could be found in treated hops and thus in beer. Hop cones were treated with 1.12 kg/ha active ingredient carbofuran (2, 3-dihydro-2, 2-dimethyl-7-benzofuranyl-N-methyl carbamate) for the control of root weevils (Otiorhynchus sulcatus, O. ovatus). The carbamates in the cones were determined using gas-liquid chromatography (GLC) and a thermionic specific detector. The percent recoveries for the carbamates ranged from 88.7 ± 5.3 to 95.3 ± 6.3% (green hops) and from 88.6 ± 12.3 to 98.0 ± 5.0% (dry hops). The phenolic metabolites were analyzed as their 2, 4-dinitrophenol ether derivatives, using GLC with an electron capture detector. The percent recoveries ranged from 85.0 ± 5.8 to 88.3 ± 8.5% (green hops) and from 80.3 ± 4.4 to 95.3 ± 3.0% (dry hops). The GLC procedure was sensitive to 0.05 ppm. Control samples in all cases contained less than 0.05 ppm and green, treated hop cones had residues of less than 0.05 ppm. Dry treated hop cones contained less than 0.05 ppm of all chemicals, except 3-keto-7-phenol (0.12 ppm) and the 3,7-diol (0.07 ppm). Although the U.S. Environmental Protection Agency (EPA) has not established tolerance levels for carbofuran and its metabolites in hop cones, the present investigation shows that residue levels on green and dry hop cones are well below the EPA's tolerances for carbofuran in other commodities.

INVESTIGATION OF CARBOFURAN AND ITS METABOLITES BY GAS-LIQUID CHROMATOGRAPHY IN GREEN AND DRY HOPS

Processed hop cones (Humulus americanus) are an important flavoring component in beer, and it is possible that carbofuran and its metabolites could be found in treated hops and thus in beer. Hop cones were treated with 1.12 kg/ha active ingredient carbofuran (2, 3-dihydro-2, 2-dimethyl-7-benzofuranyl-N-methyl carbamate) for the control of root weevils (Otiorhynchus sulcatus, O. ovatus). The carbamates in the cones were determined using gas-liquid chromatography (GLC) and a thermionic specific detector. The percent recoveries for the carbamates ranged from 88.7 ± 5.3 to 95.3 ± 6.3% (green hops) and from 88.6 ± 12.3 to 98.0 ± 5.0% (dry hops). The phenolic metabolites were analyzed as their 2, 4-dinitrophenol ether derivatives, using GLC with an electron capture detector. The percent recoveries ranged from 85.0 ± 5.8 to 88.3 ± 8.5% (green hops) and from 80.3 ± 4.4 to 95.3 ± 3.0% (dry hops). The GLC procedure was sensitive to 0.05 ppm. Control samples in all cases contained less than 0.05 ppm and green, treated hop cones had residues of less than 0.05 ppm. Dry treated hop cones contained less than 0.05 ppm of all chemicals, except 3-keto-7-phenol (0.12 ppm) and the 3,7-diol (0.07 ppm). Although the U.S. Environmental Protection Agency (EPA) has not established tolerance levels for carbofuran and its metabolites in hop cones, the present investigation shows that residue levels on green and dry hop cones are well below the EPA's tolerances for carbofuran in other commodities.

PREPARATION OF OIL RICH HOP EXTRACTS AND THEIR ADDITION TO BEER ON THE PILOT-SCALE USING LIQUID CARBON DIOXIDE*

The introduction of carbon dioxide hop extracts dissolved in liquid carbon dioxide to green beer during transfer from fermentation vessel to cold conditioning tank results in a sound dry hop flavour in the finished product. A system has been developed for injecting a solution of extract into a beer main. Extracts which are rich in hop oils are particularly suitable for imparting hop character to beer and a liquid-liquid countercurrent procedure is described for producing extract fractions containing enhanced levels of essential oil.