Hop Varieties Research Articles

Evaluation of variability of the content of alpha and beta acids in Czech bittering hop varieties (Humulus lupulus L.)

Czech bitter varieties were evaluated between 2010 and 2022. Hop varieties displayed an average content of alpha acids between 10.24% w/w (Agnus) and 13.73% w/w (Gaia). Variability below 15%, proved good stability of alpha acids content in all tested bittering hops. All varieties showed a decrease in the content of alpha acids over a period of 13 years of hop cultivation. The highest content of beta acids was determined in Gaia (7.30% w/w). In contrast, the lowest content of beta acids was found in Rubín (3.73% w/w). The new bitter genotypes Uran and 5304 had an average alpha acid content of 11.56% w/w and 10.82% w/w, respectively. Uran showed an average beta acid content of 5.47% w/w and for the genotype 5304 it was 3.61% w/w. In terms of the alpha/beta acids ratio, the hop varieties can be divided into three groups. The first group included the varieties with an alpha/beta acids ratio below 2, i.e. Vital, Boomerang and Gaia. While Agnus and Uran displayed an alpha/beta ratio slightly above 2. The highest alpha/beta ratio above 3 was found in Rubín and the 5303 genotype.

Chemical compositions and sleep-promoting activities of hop (Humulus lupulus L.) varieties.

Among natural products with sleep-promoting activity, hops have been used since ancient times as a tranquilizer and hypnotic agent. This study investigated the sleep-promoting effects of extracts of various hop (Humulus lupulus L.) varieties in invertebrate and vertebrate models. The content of α-acids, β-acids, and xanthohumol was higher in hop 70% alcohol extracts than in hop hot water extracts. Among the alcohol extracts, Citra contained a high α-acid content (229.32µg/mg), while Saphir showed high β-acid and xanthohumol content (66.37 and 4.23µg/mg, respectively). In Drosophila melanogaster, Simcoe and Mosaic water extracts and Saphir and Simcoe alcohol extracts significantly increased total nighttime sleep. Total sleep time of mice with pentobarbital-induced sleep was significantly increased by Simcoe and Mosaic water extracts and Saphir and Simcoe ethanol extracts compared to the normal group. Oral administration of Simcoe water extract and Saphir alcohol extract improved sleep in the caffeine-induced insomnia model and upregulated the mRNA expression of GABAA (gamma 2 subunit) and GABAB receptors in mouse brains. Additionally, Saphir alcohol extract significantly increased the GABA content in mouse brains. Simcoe water extract and Saphir ethanol extract modulated GABAergic signaling to improve sleep-related behaviors, including sleep duration.

Gas exchanges and morphometric measurements of a variety of hops (Humulus lupulus L.) (Cannabaceae) grown in subtropical conditions under organic and conventional management

Hops are native to the Northern Hemisphere and are widespread throughout the world; in Brazil, crops are grown on a small scale. How management differentiation can affect the physiological development of crops in subtropical climates is not well studied. The objective of this study was to evaluate the physiological and morphometric performance of five hop varieties under organic and conventional management. These experiments were conducted at Lageado Farm, at the campus of São Paulo State University in Botucatu. A 2 x 5 factorial design was adopted, with the main factor being the cultivation system (organic and conventional) and the secondary factor being the hop varieties (Cascade, Columbus, Chinook, Hallertau Mittelfrüeh and Nugget). The cultivation systems differed by fertilization and phytosanitary management. Analyses of gas exchange and chlorophyll a fluorescence were performed during the vegetative development of the plants and during branch elongation. Morphometric analyses of the plants were performed to determine the number of internodes (22.40; 18.20) and the heights of the plants (201.09; 131.07), with organic and conventional treatment, respectively. All the varieties showed satisfactory physiological and morphometric performance; however, plants grown under organic management had better results than those grown under the conventional cropping system. Lastly, we measured the potential efficiency of PSII; Hallertau M. (0.89), Nugget (0.89) and Columbus (0.88) presented the highest measurements, and the lowest values were observed in Cascade (0.86) and Chinook (0.85). In general, Hallertau M. and Columbus had the highest gas exchange values, while Cascade had the lowest.

Evaluating the Impact of High and Low Kilning Temperatures on Popular American Aroma Hops

Hop drying is an important step during the hop harvest, where hops must be quickly dried from 70–80% to 8–12% moisture to prevent deterioration of hop cones. Collaborating with hop growers in Oregon and Washington, U.S.A., the study employed commercial-scale drying experiments to investigate the impact of drying hops using static 130 °F (54 °C) and 150 °F (65 °C) air-on temperatures with six popular American aroma hop varieties (Amarillo®, Cascade, Centennial, Citra®, Mosaic®, and Simcoe®) over two harvest years, 2020 and 2021. Hop kilning temperature did not significantly impact the chemical and sensory properties of the hops. However, hop dextrin-reducing enzymes responsible for hop creep were reduced with higher kiln temperatures for all varieties over both harvest years. Drying times were significantly reduced by an average of 20-42% (2–4 h) when drying at 150 °F (65 °C) versus 130 °F (54 °C), depending on the variety. These results could benefit the hop industry by allowing hop growers greater flexibility during hop harvest and offer potential energy savings via reduced drying times.

Unusual Profile of Thiol Precursors in Special Malts: First Evidence of Chemical Glutathione-/γGluCys- and CysGly-/Cys- Conversions

Polyfunctional thiols (PFTs) present in beers or in wines are known to be released by yeast, during fermentation, from bound forms originally found in raw materials. In the brewing field, huge amounts of S-conjugates have been evidenced in several dual-purpose hop varieties. Malt, however, being the major raw material of beer, could also be a significant contributor of PFTs to beer (cysteinylated, Cys- and glutathionylated, G- precursors of 3SHol already identified in a few samples of barley and malt). Forty-two barley malts from 2 to 1500 EBC and five other malted cereals were screened to characterize their thiol precursor profile (G- and Cys- as well as dipeptidic bound CysGly- and γGluCys- forms of 3SHol). First, it was confirmed that G-3SHol was ubiquitous reaching up to 320 µg/kg in some samples, whereas Cys-3SHol remained at a trace level of up to 13 µg/ kg. Moreover, for the first time, dipeptidic bound forms of 3SHol were evidenced in malt (up to 10 and 11 µg/kg for CysGly-3SHol and γGluCys-3SHol, respectively). In pale malts, the level of the CysGly- form was shown to be proportional to that of G-3SHol (in situ γGT during the malting process). This appeared to be no longer true for special malts (ranging from 5 to 45°EBC), whose CysGly-3SHol level correlated instead with Cys-3SHol (suspected chemical conversion from the dipeptide conjugate). As for γGluCys-3SHol, it was only found in the special barley malts (indicating another chemical break of the Cys-Gly bond, here on G-3SHol) and in malted rye, spelt, and wheat. No precursors were found in roasted malt.

Proprietary Varieties’ Influence on Economics and Competitiveness in Land Use within the Hop Industry

To evaluate changes to hop industry concentration and competitiveness the Herfindahl-Hirschman Index (HHI) was used. The ownership of hop proprietary varieties, their acreage and production were compared with public varieties. Market share for each proprietary hop variety acreage and production was calculated between 2000 and 2020. The quantity of land under centralized control in the U.S. hop industry due to increased proprietary variety acreage between 2000 and 2020 was quantified. Assuming tacit collusion between the participants in the oligopoly, the HHI enabled us to quantify the portion of land under oligopoly control. The HHI analysis of hop acreage and hop production demonstrated that market concentration rose rapidly between the years 2010 (0.0376 and 0.0729) and 2020 (0.4927 and 0.5394). This resulted in decreasing business competitiveness within the market during this period caused primarily by rapid consolidation of ownership during increased proprietary variety acreage and production increases. Calculations revealed that in 2016 a tipping point had been reached concerning market concentration, which resulted in higher sustained season average prices of hops—a key raw material in brewing.

The Stability of Hop (Humulus lupulus L.) Resins during Long-Period Storage

The stability of alpha-acids, beta-acids and hop storage index (HSI) values under different conditions (aerobic/anaerobic, 4 °C/room temperature) was studied in a two-year trial. Six different varieties (Celeia, Aurora, Bobek, Styrian Gold, Savinjski Golding and Styrian Wolf) were used in the form of cones and pellets. Alpha- and beta-acids were determined by HPLC and HSI by spectrophotometry. Anaerobic conditions at 4 °C were best for alpha-acids, beta-acids and HSI values; however, 10-35% of the alpha-acids were still lost after two years. The decline was greater (63-99%) under aerobic conditions and at room temperature. Alpha-/beta-acid ratios increased in hop cones and decreased in hop pellets, whereas HSI values increased in all storage conditions. Overall, the performance was better for pellets than for hop cones. Storage conditions, storage form and hop variety had significant effects on the stability of hop resins.

A different approach to hop growing

The current study aimed to examine how various growers in the Czech Republic hop-growing regions approached the production of hops (Saaz variety). The work also keeps track of how different growers approach fertilization and nutrition, as well as how often plant protection chemicals containing these ingredients are used. The Saaz hop variety samples from the primary Czech hop-growing regions, gathered in 2020 and 2021, were assessed. The average spindle length (14–18 mm), average number of spindle segments (9.3–11.9 pcs/needle) and conductometric parameters (2.7–4.7% w/w) in the samples were identified.

Bring Us in Good Ale

AbstractThis essay documents the century-long efforts of Peter Darby, Ernest S. Salmon, and Ray Neve, all of whom were directors of England's Hop Research Program. While these scientists engaged in myriad projects, the central story surrounds the development and release of hybrid hop varieties for use in beer. In contrast with the brewing industry that turned toward mechanization and industrial advancements in the twentieth century, the English hop breeding program steadily relied on hand-pollinating characteristic of Mendelian genetics. Crossbreeding, or hybridization, of hops (and scores of other dioicous plants—that is, those with two distinct sexes) traditionally occurred with scientists selecting specimens that exhibited desirable traits that could be traced to their hereditary makeup. The process was painstakingly slow, requiring countless dustings of pollen from male plants onto female flowers. Darby, Salmon, and Neve engaged in this process thousands of times before deciding on which offspring to select from the greenhouses to transplant into fields. Their promising and successful specimens today populate England's experimental hop garden for their potential in brewing or breeding future crosses; the most outstanding progeny can be found in beers near and far.

Single and Interactive Effects of Unmalted Cereals, Hops, and Yeasts on Quality of White-Inspired Craft Beers

White beers owe their name to their straw yellow colour deriving from the use of unmalted wheat, which also supplies a relatively high protein content causing haze formation. This study aimed to develop white-inspired craft beers made with combinations of three mixtures of barley malt/unmalted wheat (alternatively durum-var. Dauno III, soft-var. Risciola, or emmer-var. Padre Pio), two hop varieties (Cascade or Columbus), and two Saccharomyces cerevisiae strains (Belgian yeast and a high-ester producing yeast); and assess the single and interactive effects of these ingredients on physical, chemical, and sensory characteristics of the beers. According to the graphical representation of the results for the Principal Component Analysis, most of the samples appear overlapped since they had similar characteristics, but it was possible to highlight two clusters of beers different from the others: those produced with (a) Risciola wheat and Columbus hop and (b) Dauno III wheat, Cascade hop, and the Belgian yeast. The beers of these clusters obtained the highest scores for their overall quality that, in turn, was positively correlated with concentrations of citric acid, 4-hydroxybenzoic acid, syringic acid, and epicatechin; alcohol %, colour, amount and persistence of foam, intensity of fruity flavour, and body.

Desempenho agronômico de variedades de Humulus lupulus L. cultivadas em sistema orgânico e convencional no centro-oeste paulista, Brasil

ABSTRACT: Hop is a multifunctional specie; however, a large part of its production is destined for the beer market. In Brazil, all hop demand is imported, which has aroused interest in national production. Genetic material and cultivation systems can influence hops production. Thus, this study evaluated morphological and productive performance of hop varieties grown under organic and conventional management in the central-west region of São Paulo, Brazil. The hop yard was installed in the experimental area of the FCA/UNESP (São Paulo State University, School of Agriculture) - Botucatu, in November 2018, the data were collected in second year of production. A randomized block design was adopted, in 2 x 5 Split-Plot, being the main factor: cultivation systems (organic and conventional), and secondary factor: hop varieties (Columbus, Chinook, Nugget, Cascade, and HallertauMittelfrüeh), with four blocks and four plants per plot. Crop-specific morphological and productive parameters were evaluated. The results showed no significant influence of cultivation systems in morphological parameters. Regarding the varieties, Chinook, Cascade, and Nugget stand out for cone length. Columbus, Chinook and Cascade showed higher yields when grown in organic system, obtaining 1100.66, 1088.27 and 940.40 g of cones per plant, respectively. While, HallertauMittelfrüeh variety was the least productive in both systems, in organic system with 160.50 g per plant production, and 267.84 g per plant in conventional system, and, also showing lower cycle compared to the others.

Antimicrobial Properties of Different Hop (Humulus lupulus) Genotypes

The antimicrobial activity of hop extracts obtained from different hop genotypes were investigated against Staphylococcus aureus and Lactobacillus acidophilus. In this study the pure xanthohumol, purified β-acids rich fraction, as well as α-acids with β-acids rich fraction were used to test antimicrobial activity against Staphylococcus aureus and Lactobacillus acidophilus; whereby, the antimicrobial activity of different hop extracts against Lactobacillus acidophilus was studied for the first time. Microbial susceptibility to purified hydroacetonic extracts from different hop varieties was investigated by the broth microdilution assay to determine the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). The hop hydroacetonic extracts were more effective against Staphylococcus aureus than against Lactobacillus acidophilus. Strong inverse correlations of MIC and MBC values were obtained with xanthohumol, cohumulone, n+adhumulone, colupulone and n+adlupulone contents, suggesting that the identified chemical hop compounds are directly responsible for antimicrobial effects. Moreover, the effect of the growth medium strength on the MIC values of hop extracts against Staphylococcus aureus was systematically investigated for the first time. The current study also reveals the effect of different hop extracts on Staphylococcus aureus, which responds to their presence by lag phase extension and generation time prolongation.

Evaluation of hop yield stability in Czech bitter hop varieties

Between the years 2011 and 2022, the Czech hop varieties Agnus, Rubín, Vital, Gaia and Boomerang were evaluated in terms of their hop yield. The highest hop yield was recorded in Gaia (2.99 kg/plant) and Vital (2.92 kg/plant). Boomerang had the lowest yield (2.11 kg/plant.). The lowest variability of yield was determined in Vital (19.74%) and the highest in Boomerang (33.29%) and Agnus (32.98%). Vital demonstrated the lowest decreasing trend of hop yield over a period of 12 years. Rubín showed the highest decreasing trend.

Hydrolats from Humulus lupulus and Their Potential Activity as an Organic Control for Varroa destructor

Varroa destructor is a parasitic mite, which is considered a severe pest for honey bees causing serious losses to beekeeping. Residual hydrolats from steam extraction of hop essential oils, generally considered as a waste product, were tested for their potential use as acaricides on V. destructor. Four hop varieties, namely Cascade, Spalt, Victoria, and Mapuche, showed an interesting performance as feasible products to be used in the beekeeping industry. Some volatile oxidized terpenoids were found in the hydrolats, mainly β-caryophyllene oxide, β-linalool, and isogeraniol. These compounds, together with the presence of polyphenols, flavonoids, and saponins, were probably responsible for the promissory LC50 values obtained for mites after hydrolat exposition. Victoria hydrolat was the most toxic for mites (LC50: 16.1 µL/mL), followed by Mapuche (LC50 value equal to 30.1 µL/mL), Spalt (LC50 value equal to 114.3 µL/mL), and finally Cascade (LC50: 117.9 µL/mL). Likewise, Spalt had the highest larval survival, followed by Victoria and Mapuche. Cascade was the variety with the highest larval mortality. In addition, none of the extracts showed mortality higher than 20% in adult bees. The Victoria hydrolat presented the best results, which makes it a good compound with the prospect of an acaricide treatment against V. destructor.

Effect of Hop Varieties and Forms in the Hopping Process on Non-Alcoholic Beer Quality.

The aim of this study was to determine how the hopping technique affects the quality of non-alcoholic beer (NAB). A series of NABs were brewed and tested for basic physicochemical characteristics, profiles of selected volatile compounds, and microbial contamination. The brewing process yielded 13 experimental groups of beers, all of which had an ethanol content of <0.5%v/v. Among the batches brewed with ‘Marynka’ hops, the pellet form was found to provide the highest concentrations of hop-derived volatile compounds, whereas in the ‘Magnum’ groups, the extracts and whole hops proved superior. Humulene and caryophyllene were the primary volatiles in terms of quantity. All the brews were contamination-free—no microbes other than yeast cells were detected. Their microbiological purity was also supported by an assay of beer-defect indicators (volatile compounds), which only showed low levels of acetaldehyde, 1-propanol, 2-methylbutanol, and 3-methylbutanol. The hopping technique deployed was found not to affect the physicochemical parameters of NABs, but did have a significant impact on their volatile compound profile.

Alzheimer's Disease Prevention through Natural Compounds: Cell-Free, In Vitro, and In Vivo Dissection of Hop (Humulus lupulus L.) Multitarget Activity.

The relevant social and economic costs associated with aging and neurodegenerative diseases, particularly Alzheimer's disease (AD), entail considerable efforts to develop effective preventive and therapeutic strategies. The search for natural compounds, whose intake through diet can help prevent the main biochemical mechanisms responsible for AD onset, led us to screen hops, one of the main ingredients of beer. To explore the chemical variability of hops, we characterized four hop varieties, i.e., Cascade, Saaz, Tettnang, and Summit. We investigated the potential multitarget hop activity, in particular its ability to hinder Aβ1-42 peptide aggregation and cytotoxicity, its antioxidant properties, and its ability to enhance autophagy, promoting the clearance of misfolded and aggregated proteins in a human neuroblastoma SH-SY5Y cell line. Moreover, we provided evidence of in vivo hop efficacy using the transgenic CL2006Caenorhabditis elegans strain expressing the Aβ3-42 peptide. By combining cell-free and in vitro assays with nuclear magnetic resonance (NMR) and MS-based metabolomics, NMR molecular recognition studies, and atomic force microscopy, we identified feruloyl and p-coumaroylquinic acids flavan-3-ol glycosides and procyanidins as the main anti-Aβ components of hop.

Analytical determination of antioxidant capacity of hop-derived compounds in beer using specific rapid assays (ORAC, FRAP) and ESR-spectroscopy

There is a relationship between antioxidant activity and ageing stability of beer. The high-throughput antioxidant capacity assays ORAC and FRAP, which rely on specific reaction mechanisms, are validated as an addition to the established ESR-ST method with a focus on hop-derived antioxidants. Beers were brewed with systematic variations in hop variety, hop product, and the hopping regime (late hopping) to achieve sample beers varying widely in the concentrations of hop-derived antioxidants (α- and iso-α-acids, phenolic compounds). A significant positive correlation between phenolic compounds and the ORAC- and FRAP-values (p < 0.01) was found. The effect of individual resinous substances and free phenolic acids and flavonoids on the antioxidant capacity of beer (ORAC, FRAP, and ESR-ST) was proven in spiking trials. We found a correlation between the occurrence of the o-di-OH-group and the ORAC- and FRAP-values of phenolic compounds. Phenolic compounds did not react as anti- or prooxidants in the radical generation (ESR-ST). Higher concentrations of unisomerized α-acids significantly reduced ESR-signal intensity but had no significant effect on ORAC- or FRAP-values. Beers brewed with late hop addition, which yielded higher concentrations of unisomerized α-acids and phenolic compounds, had higher ORAC, FRAP-values and a reduced ESR-signal intensity. These three methods rely on different reaction principles, and therefore, different groups of hop-derived compounds act as antioxidants in these assays. A combination of the two high-throughput methods (ORAC, FRAP) and ESR-ST is advantageous for the evaluation of the antioxidant capacity of beers varying in hop-derived compounds.

Evaluation of fine aroma Saaz Shine hop variety

The Saaz Shine variety was registered in 2019. It was tested in two areas, Chrášťany (no irrigation) and Stekník (with irrigation), between 2017 and 2021. An average hop yield in Stekník is 2.62 t/ha and in Chrášťany it is 2.54 t/ha. No conclusive difference in yields was determined. An average content of alpha acids was 4.67% in Chrášťany and 3.18% in Stekník, therefore the content of alpha acids in Saaz from Chrášťany has been proven to be higher than in Stekník. There is a conclusively higher content of essential oils in hops from Chrášťany (0.65g/100 g) than from Stekník (0.34 g/100 g), but the composition of the essential oils is not conclusively different. The aroma of hop cones from both areas is identical. Their moderately intense scent can be described as a fine hop one with a background hint of fruit and citrus.

Changes in Hop (Humulus lupulus L.) Oil Content and Composition during Long-Term Storage under Different Conditions.

Hop essential oil, in addition to alpha-acids, is one of the most valuable parameters for brewers, since it is responsible for beer aroma. The hop oil content and hop oil chemical composition deliver various aromas to beer. During storage, the hop chemical composition undergoes many physical and chemical changes that impact its quality. The main purpose of our study was to evaluate the changes occurring in hop oil content and its chemical composition during two years of storage under four different conditions (anaerobic, aerobic, cold room (4 °C), and room temperature) in the form of cones and pellets, supplied by local suppliers in Slovenia. Hop oil content and composition were determined by steam distillation and GC-FID. The greatest decrease in hop essential oil content occurred when the hops were stored under aerobic conditions and at room temperature. Monitoring of eight hop oil compounds under various conditions revealed different behaviors of the changes. The best storage conditions were anaerobic at low temperatures. Oxygen resistance was lower for pellets than for hop cones, whereas high temperature was more devastating for hop cones. In addition to the storage conditions, the hop variety and form were important factors regulating the extent of changes in hop oil content and chemical composition.

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

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