Hop Resins Research Articles

The Comparison and Brewing Value of Saaz Hop Pedigree

The well-known hop variety, Saaz, which gives the Pilsner lager beer its characteristic hop aroma, may be threatened by climate change in the future. Therefore, new Saaz-related hop varieties, including Saaz Late, Saaz Brilliant, Saaz Comfort, and Saaz Shine, were recently bred. A comparison study was carried out to evaluate whether these varieties are acceptable for traditional lagers. For this purpose, sensorial and chemical analyses of hops and related beers, namely, an analysis of hop resins and oils, were performed. Sensory profiles of Saaz varieties are very similar (fine, hoppy aroma; floral; herbal), except for Saaz Comfort, which has a slightly higher aroma intensity, and Saaz Shine, which has the most noticeable fruity scent, with traces of citrus. The chemical profiles are also very similar, with α-humulene, β-pinene, (E)-β-farnesene, β-caryophyllene, and myrcene being the most abundant. Decoction mashing and kettle hopping technology with bottom fermentation show that the compared varieties result in very similar lager beers with hoppy, floral, herbal, fruity, and spicy aromas. Typical hop oils include farnesol, linalool, methyl geranate, β-pinene, and limonene. The high concentration of farnesol in beer correlates with the concentrations of (E)-β-farnesene and farnesol in hops. New Saaz varieties are widely used to produce Pilsner lager without affecting the traditional sensory aroma of this widespread style. Varieties have a higher yield of approximately 25% and bitter acid concentrations of approximately 15%, with Saaz Comfort comprising approximately 100%. Furthermore, the concentration of hop oils is approximately 40% higher in Saaz Shine than a traditional Saaz variety. Moreover, Saaz Shine and Saaz Comfort have very good resistance to drought, which is an important property from a climate change perspective.

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.

BEER AS A SOURCE OF HOP PRENYLATED FLAVONOIDS, COMPOUNDS WITH ANTIOXIDANT, CHEMOPROTECTIVE AND PHYTOESTROGEN ACTIVITY

Beer is an alcoholic beverage consumed worldwide, which is given its typical taste by the presence of hops. Hops contain an array technologically important substances, which are primarily represented by hop resins (humulones, lupulones, humulinones, hulupones, etc.), essential oils (humulene, myrcene, etc.) and tannins (phenolic compounds quercetin, catechin, etc.). In addition to their sensory properties, these molecules contribute to the biological and colloidal stability of beer with their antiseptic and antioxidant properties. Recently, an increased attention has been given to prenylated hop flavonoids, particularly xanthohumol, isoxanthohumol and 8-prenylnaringenin. Xanthohumol is a prenylated chalcone that exhibit antioxidant, anticancer and chemoprotective effects. Its only source in human nutrition is beer, nevertheless a large part of xanthohumol from hops is isomerized by heat to isoxanthohumol and desmethylxanthohumol, from which a racemic mixture of 6- and 8-prenylnaringenins is formed during the beer production. Xanthohumol is also converted to isoxanthohumol by digestion, leading to the formation of 8-prenylnaringenin that is being catalyzed by the enzymes of the intestinal microorganisms as well as liver enzymes. This substance is currently considered to be the most effective natural phytoestrogen.

Assessment of the Suitability of Aromatic and High-Bitter Hop Varieties (Humulus lupulus L.) for Beer Production in the Conditions of the Małopolska Vistula Gorge Region

The aim of the study was to assess the yield of cones and the quality of six hop varieties (“Iunga”, “Lubelski”, “Sybilla”, “Magnum”, “Lomik”, “Marynka”) in terms of their suitability for beer production, under the conditions of the Małopolska Vistula Gorge Region (21°53′ E; 51°16′ N) (2015–2017). The scope of the research included the determination of the yield of cones and their physicochemical properties, as well as determination of the contents of hop resins and essential oils. In bitter varieties, the ratio of alpha-acids to beta-acids was stable, while, in aromatic varieties, it was variable. In the essential oils of the studied hop varieties, compounds with myrcene and α-humulene were identified and dominated the profiles. “Iunga”, “Sybilla”, “Lubelski”, and “Lomik” were rich in monoterpene hydrocarbons, mainly myrcene, while there was a bit more α-humulene in the “Marynka” variety. “Magnum” was characterized by an even distribution of monoterpenes and sesquiterpenes. The “Magnum variety turned out the most useful for the brewing industry in this region. The Małopolska Vistula Gorge Region is a region where hops not only achieve a high yield of cones, but also good-quality. The bitterness and aroma content of the hops in this region is high.

Incorporation of natural and mechanically ruptured brewing yeast cells in beef burger to replace textured soy protein.

The use of brewer`s yeast to replace textured soy protein (TSP) in burgers was investigated. Three formulations were made, corresponding to a control formulation with 4% TSP, a formulation containing 4% yeast cells in their natural state, and a formulation made with 4% mechanically ruptured yeast cells, which were characterized for the chemical, technological, and sensory properties. Significant differences were observed for pH and instrumental color between the formulations, with no changes in the visual color evaluation by the untrained assessors. The addition of yeast cells resulted in a higher cooking yield and lower reduction in diameter, contributing to maintaining the shape and juiciness of burgers, which is a positive aspect from the technological point of view. The TSP-based formulation presented higher overall appearance and flavor scores when compared with the other formulations, with no significant differences for the other sensory attributes. The results showed that debittering of yeast-cell biomass is required to remove hop resins and tannins before using in burgers, aimed to improve the product`s acceptance and the purchase intent. The debittered yeast cell biomass can be used in burger formulations with great potential to replace TSP, as an alternative to obtain a free allergen meat product.

Morphological and Biochemical Characterization of Wild Hop (Humulus lupulus L.) Populations from Banja Luka Area (Bosnia and Herzegovina)

This study aims to do a morphological and biochemical characterization of selected wild hop populations from the Banja Luka region, as plant material with potential value for introduction into plant selection. Female inflorescences (cones) from seven populations (DKH3, DKH5, DKH6, DKH8, DKH9, DKH10, and DKH11) were sampled in 2018 and 2019. Hop cones were collected in October 2018 and 2019 for morphological characterization, when 50 cones per population were analyzed, and also the cones were collected in mid-September in 2019 for biochemical characterization. Morphological parameters were carried out for: cone length (cm), number of nodes per cone spindle, cone density, and number of seeds per cone, all important agronomic characters in hop production. Also, 27 components of essential oil and 6 components of hop resins were analyzed. Statistical analysis of morphological characteristics was performed by factorial analysis of variance (year × population), and the significance of individual differences was determined by LSD test. The grouping of examined hop populations according to the manifested morphological characteristics was performed by cluster analysis. Statistical analysis for biochemical characteristics was performed by analysis of variance, and the significance of the differences was tested by Tukey’s statistical test. In order to determine similarities between different population multivariant statistical method Principal component analysis (PCA) was applied. According to morphological and biochemical analysis, DKH6 hop population is singled out as the most valuable for hop breeding.

Ploidy variation and agronomic performance of F1 hybrids of tetraploid and diploid forms of Humulus lupulus L.

Humulus lupulus (2n = 2x = 20) as a source of hop resins, essential oils and polyphenols has value in brewing, pharmacy and cosmetology. Conventional crossing between tetraploids of ‘Sybilla’ and diploid males were performed to obtain F1 hybrids. Cytological studies revealed that 83.8% of the hybrids were triploids (2n = 3x = 30), 15.2% were aneuploids in which the chromosome number ranged from 28–32. Tetraploids (2n = 4x = 40) and diploids were also observed, which indicates numerous disturbances of gametogenesis of the parental forms. STS markers specific for male plants showed that females outnumbered male individuals among the F1 hybrids, which is in accordance with the distribution of sex ratio characteristic for diploid hybrids of H. lupulus. Female triploids were compared to the control ‘Sybilla’ with regard to their functional characteristics and alpha acids content in cones. A two year-long experiment showed that most of the triploids had a significantly higher position of fructiferous branches and shoot twist index compared to diploids of ‘Sybilla’. There was also a significantly extended time for them to reach technological maturity of cones. Triploids were distinguished by a significantly lower seed content compared to ‘Sybilla’, therefore the raw material obtained from them is more suitable for the production of hop pellets and extracts.

Antilisterial effects of hop alpha and beta acids in turkey slurry at 7 and 37°C.

Chemical components of hop resins effectively inhibit the growth of L. monocytogenes in microbiological culture media. This study was conducted to investigate antilisterial activities of hop α- and β-acid in turkey slurry. Turkey slurries were inoculated with L. monocytogenes, formulated with hop α- or β-acid from 0 to 1,000ppm, and incubated at 37°C for 24h or at 7°C for 12 days. During storage at 37°C for 24h, L. monocytogenes populations were reduced from 2.40 log CFU/g to non-detectable (<1 log CFU/g) in α-acid at ≥750ppm and β-acid at 1,000ppm, whereas the control (0ppm) allowed the pathogen to grow to 8.0 log CFU/g. During storage at 7°C for 12 d, the slurry treated with α-acid at ≥100ppm and β-acid at ≥500ppm showed listeristatic effects, while listericidal effects were observed in the slurries at 1,000ppm, regardless of hop acid type. Hop α-acid ≤ 50ppm and β-acid ≤ 100ppm failed to inhibit L. monocytogenes, and the pattern of bacterial growth was similar to that of control with no significant difference (P >0.05). Based on these results, the concentration of α-acid >100ppm or β-acid >500ppm is minimally required to inhibit L. monocytogenes when turkey batters are formulated with hop acids as a single antilisterial agent prior to cooking and storage at 7°C.

A kinetic study of xanthohumol cyclization to isoxanthohumol – A role of water

Xanthohumol, a major prenylated chalcone found in hop resin, has recently attracted scientific interest due to its health-promoting properties. In the present work, we investigated the mechanism of xanthohumol cyclization to isoxanthohumol in an aqueous solution with a high pH by means of UV–Vis spectroscopy and liquid chromatography. The results were modeled by DFT methods with the SMD solvation model. The results of theoretical calculations were consistent with experimental data. The proposed mechanism comprises two stages, where the first step involves cyclization of xanthohumol ions and the second step involves the addition of H+ ion from a water molecule to an isoxanthohumol ion. The second step is responsible for the stabilization of isoxanthohumol. Based on these results some practical information can be drawn, which may be important from the point of view of the problem xanthohumol stability in commercial dietary supplements.

Humulus lupulus- a story that begs to be told. A review

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 (α- and β-acids) and the latest findings on the absolute configuration of the cis and trans iso-α-acids are discussed. Special attention is given to the hard resins; the known δ-resin is reviewed and the e-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

Classification of commercial cultivars of Humulus lupulus L. (hop) by chemometric pixel analysis of two dimensional nuclear magnetic resonance spectra

The development of fast and effective spectroscopic methods that can detect most compounds in an untargeted manner is of increasing interest in plant extracts fingerprinting or profiling projects. Metabolite fingerprinting by nuclear magnetic resonance (NMR) is a fast growing field which is increasingly applied for quality control of herbal products, mostly via 1D 1H NMR coupled to multivariate data analysis. Nevertheless, signal overlap is a common problem in 1H NMR profiles that hinders metabolites identification and results in incomplete data interpretation. Herein, we introduce a novel approach in coupling 2D NMR datasets with principal component analysis (PCA) exemplified for hop resin classification. Heteronuclear multiple bond correlation (HMBC) profile maps of hop resins (Humulus lupulus) were generated for a comparative study of 13 hop cultivars. The method described herein combines reproducible metabolite fingerprints with a minimal sample preparation effort and an experimental time of ca. 28 min per sample, comparable to that of a standard HPLC run. Moreover, HMBC spectra provide not only unequivocal assignment of hop major secondary metabolites, but also allow to identify several isomerization and degradation products of hop bitter acids including the sedative principal of hop (2-methylbut-3-en-2-ol). We do believe that combining 2D NMR datasets to chemometrics, i.e. PCA, has great potential for application in other plant metabolome projects of (commercially relevant) nutraceuticals and or herbal drugs.

Identification and Quantification of the Oxidation Products Derived from α-Acids and β-Acids During Storage of Hops (Humulus lupulus L.)

α-Acids and β-acids, two main components of hop resin, are known to be susceptible to oxygen and degraded during hop storage, although the oxidation products in stored hops have not been fully identified. In this study, we developed a high-performance liquid chromatography (HPLC) analysis method suitable for separation and quantification of the oxidation products. This HPLC analysis clearly proved, for the first time, that humulinones and hulupones are major products in oxidized hops. We are also the first to identify novel 4'-hydroxy-allohumulinones, suggested to be oxidative products of humulinones, by means of NMR spectroscopy and high-resolution mass spectrometry. Using the developed analytical method, changes in α- and β-acids and their oxidation products during hop storage were clearly revealed for the first time.

Assessment of changes in hop resins and polyphenols during long-term storage

storage without air access at +2C. Storage at +20 Cr esulted in afinal loss of 20–25% a-acids, but the content of b-acids did not changesignificantly. Large decreasesina-acids (64–88%)and inb-acids (51–83%)were found inhops storedwith access toairat +20C. The rate of decline accelerated markedly after 6 months of storage. In terms of hop resin changes, Premiant and Sladek were the most and the least stable varieties, respectively. After 12 months, the content of the total polyphenols and flavonoids decreased by 30–40% and by 20–30%, respectively, irrespective of storage conditions. The rate of decline accelerated strongly after6months.The DPPH(1,1-diphenyl-2-picrylhydrazyl)antiradicalpotentialdecreasewassignificantonlyinhopsstoredunder aerobic conditions. The depletion was 9–25% after 1 year; Saaz was the most stable variety. Copyright © 2012 The Institute of Brewing & Distilling

The molecular organization of prenylated flavonoid xanthohumol in DPPC multibilayers: X-ray diffraction and FTIR spectroscopic studies

Xanthohumol (XN) is the major prenylated flavonoid found in hop resin. It has attracted considerable attention in recent years due to its wide spectrum of biological activities and the beneficial effect on human health. Since lipid membrane is first target for biologically active compounds, we decided to investigate the influence of XN on the dipalmitoylphosphatidylcholine (DPPC) multibilayers. Interactions of XN with DPPC were investigated as a function of temperature and its concentration by using X-ray diffraction and the ATR-FTIR spectroscopy techniques. The aim of understanding the mechanisms of molecular interactions between XN and DPPC was to indicate the localization of the XN with respect to the membrane and the type of interaction with phospholipids. The results revealed that XN changes the physical properties of the DPPC multibilayers in the form of dry film. A new complex formation between XN and DPPC is reported. The detailed analysis of refraction effect indicates the changes in electron density ratio between hydrophobic and hydrophilic zones of lipid at phase transition. This is in compliance with reported changes in FTIR spectra where at pretransition XN moves from interface region between polar heads to the neighborhood of phosphate groups.

Cytotoxic effect of commercial Humulus lupulus L. (hop) preparations – In comparison to its metabolomic fingerprint

Hops (Humulus lupulus L. Cannabaceae) is an economically important crop, that has drawn more attention in recent years due to its potential pharmaceutical applications. Bitter acids (prenylated polyketides) and prenylflavonoids are the primary phytochemical components that account for hops resins medicinal value. We have previously reported on utilizing untargeted NMR and MS metabolomics for analysis of 13 hops cultivars, revealing for differences in α- versus β-bitter acids composition in derived resins. In this study, effect of ratios of bitter α- to β-acids in hop resins to cytotoxicity of hop resins was investigated. In vitro cell culture assays revealed that β-acids were more effective than α-acids in growth inhibition of PC3 and HT29 cancer cell lines. Nevertheless, hop resins enriched in β-acids showed comparable growth inhibition patterns to α-enriched resins and suggesting that bioactivity may not be easily predicted by metabolomics and/or gross metabolic profiling in hops.

The Sedative Effect of Non-Alcoholic Beer in Healthy Female Nurses

IntroductionThe hop (Humulus lupulus L.), a component of beer, is a sedative plant whose pharmacological activity is principally due to its bitter resins, in particular to the α-acid degradation product 2-methyl-3-buten-2-ol. The mechanism of action of hop resin consists of raising the levels of the neurotransmitter γ-aminobutyric acid (GABA), an inhibitory neurotransmitter acting in the central nervous system (CNS).ObjectivesTo analyze the sedative effect of hops as a component of non-alcoholic beer on the sleep/wake rhythm in a work-stressed population.MethodsThe experiment was conducted with healthy female nurses (n = 17) working rotating and/or night shifts. Overnight sleep and chronobiological parameters were assessed by actigraphy (Actiwatch®) after moderate ingestion of non-alcoholic beer containing hops (333 ml with 0,0% alcohol) with supper for 14 days (treatment). Data were obtained in comparison with her own control group without consumption of beer during supper.ResultsActigraphy results demonstrated improvement of night sleep quality as regards the most important parameters: Sleep Latency diminished (p≤0.05) in the Treatment group (12.01±1.19 min) when compared to the Control group (20.50±4.21 min), as also did Total Activity (p≤0.05; Treatment group = 5284.78±836.99 activity pulses vs Control = 7258.78±898.89 activity pulses). In addition, anxiety as indexed by the State-Trait Anxiety Inventory (STAI) decreased in the Treatment group (State Anxiety 18.09±3.8 vs Control 20.69±2.14).ConclusionThe moderate consumption of non-alcoholic beer will favour night-time rest, due in particular to its hop components, in addition to its other confirmed benefits for the organism.

From Waste to Superbrand: The Uneasy Relationship between Vegemite and Its Origins

From Waste to Superbrand: The Uneasy Relationship between Vegemite and Its Origins

Construction of gene expression system in hop ( Humulus lupulus) lupulin gland using valerophenone synthase promoter

The promoter region of the valerophenone synthase (VPS) gene was isolated from hop (Humulus lupulus). VPS, a member of the chalcone synthase (CHS) super-family, catalyzes the biosynthesis reaction of the hop resin that significantly accumulates in the cone's secretory gland called the "lupulin gland". The typical H-box and G-box sequences, which exist in many plants' CHS promoters and act as cis-elements for tissue specificity, UV-light induction, etc., were not found in the isolated VPS promoter, although the H-box-like sequence (CCTTACC, CCTAACC) and the core sequence (ACGT) of the G-box were observed. The transformation experiment using the VPS promoter-UIDA gene fusion revealed that the promoter acts not only in the lupulin gland but also in the glands of leaf and stem. On the other hand, the VPS promoter activity was not induced by UV-irradiation.

Automated sample preparation by pressurized liquid extraction–solid-phase extraction for the liquid chromatographic–mass spectrometric investigation of polyphenols in the brewing process

The analysis of polyphenols from solid plant or food samples usually requires laborious sample preparation. The liquid extraction of these compounds from the sample is compromised by apolar matrix interferences, an excess of which has to be eliminated prior to subsequent purification and separation. Applying pressurized liquid extraction to the extraction of polyphenols from hops, the use of different solvents sequentially can partly overcome these problems. Initial extraction with pentane eliminates hydrophobic compounds like hop resins and oils and enables the straightforward automated on-line solid-phase extraction as part of an optimized LC–MS analysis.

Hop Latent Viroid (HLVd)-Caused Pathogenesis: Effects of HLVd Infection on Lupulin Composition of Meristem Culture-Derived Humulus lupulus

Season-dependent fluctuation of hop latent viroid in meristem tips enabled selection of viroid-free cultures from Osvald's clone 31, 72, 114, and cv. Premiant. These mericlones were used to evaluate effect of viroid infection on the composition of hop resins and essential oils in the first production year. Healthy plants were compared with naturally re-infected individuals under field conditions. On average, viroid infection decreased content of α-bitter acids by 40 %. The content of β-bitter acids, as well as the ratios of humulone/cohumulone and lupulone/colupulone was not influenced by viroid infection. The content of all monoterpenes was for 29, 37.4 and 41.6 % higher for myrcene, α- and β-pinene, respectively, in infected plants compared with the healthy controls. The contents of sesquiterpenes like β-caryophyllen α-humulene, α-copaene, γ-muurolene, β-bisabolene, γ-cadinene, and δ-cadinene decreased by 13.7, 13, 14, 18.5, 29, 21.7 and 18.5 %, respectively, due to viroid infection. The possible influence of some oxidative-reduction processes activated by viroid-caused pathogenesis was assumed to be involved in the accumulation of terpenes alcohols like geraniol and methylgeranate, and in the reduction of the contents of the majority of ketones detected in the spectra of essential oils.