Search Results (80)

The paper concerns a study of drying and the creation of a statistical model for measuring the relative humidity of the drying environment in a belt dryer, as well as the moisture content of hop heads, stems, and bracts. The SAAZ variety was used, which is widely cultivated in the Czech Republic, and the data from harvesting seasons since 2017 were recorded. The findings demonstrated the influence and dependence of the moisture content of hop cones and their parts on the relative humidity of the drying environment in a belt dryer of hops. This dependence was confirmed by a statistical analysis of the measured values. Furthermore, a quadratic model was developed based on measurements taken over three harvest seasons. The model is applicable to predict the moisture content of the hops at a given location based on the relative humidity of the drying environment in the belt dryer and could be useful for developing an automatic hop-drying system. Full article

Humulus lupulus, commonly known as hop, is a climbing plant whose female cones impart beer’s characteristic bitterness and aroma and also serve as a preservative. In this study, we conducted a meta-analysis to investigate the antimicrobial activity of hop compounds and extracts against various microorganisms by statistically synthesizing minimum inhibitory concentration (MIC) values. From the 2553 articles retrieved from the comprehensive literature search, 18 provided data on MIC values for six hop compounds, and three extract types tested against 55 microbial strains’ MIC values corresponded to 24 and 48 h incubation periods with compounds or extracts. The results indicate that xanthohumol (a flavonoid) and lupulone (a bitter acid) exhibit potent antimicrobial activity against most tested microorganisms, particularly food spoilage bacteria [21.92 (95%CI 9.02–34.83), and 12.40 (95%CI 2.66–22.14) μg/mL, respectively, for 24 h of treatment]. Furthermore, hydroalcoholic extracts demonstrated greater efficacy compared to supercritical CO₂ (SFE) extracts, which showed limited antimicrobial effects against both probiotic and non-probiotic strains. These findings underscore the need for standardized, evidence-based protocols—including uniform microbial panels and consistent experimental procedures—to reliably evaluate the antimicrobial properties of hop-derived compounds and extracts. Taken together, our findings ultimately chart a path toward evidence based antimicrobial tests that could inform food-preservation strategies and inspire the development of plant-based antimicrobials. Full article

Hops (Humulus lupulus L.) are a critical component in beer brewing. The growing demand for craft beer has increased interest in hop cultivation in non-traditional regions where unfavorable climatic conditions hinder optimal yield and quality. To address these challenges, this study investigates the effects of plant growth regulators (PGRs) on hop cone yield and chemical compositions. In two separate studies, year-1 Cascade hops were subjected to various PGR treatments in the field. PGR treatments generally had minimal effect on the dry cone yield in study I. In study II, a combination of Ethephon at 45 mg/L and ProGibb at 3 mg/L significantly increased the cone yield by 125% compared to the control. While all treatments had a “good quality” hop storage index, a combination of Ethephon and ProGibb produced alpha acid percentages within the commercial standard range. Ethephon at 30 mg/L combined with ProGibb at 2 mg/L enhanced bitterness and aroma, delivering the highest concentration of volatile organic compounds at 569.7 mg/L, thereby enhancing aroma compounds associated with fruity esters, monoterpenes, and sesquiterpenes. This study demonstrates that specific PGR treatments can improve the chemical composition of hops grown in non-traditional regions, with implications for optimizing aroma and bitterness in beer. Full article

This study investigates the use of hop cone residues as a sustainable alternative to peat in seed coating formulations for the delivery of biocontrol agents such as Trichoderma. Some native isolates, T. velutinum T029 and T. harzianum T019 and T059, were tested for their development on peat and hop residues using qPCR. The results showed significantly higher fungal growth in hop cones, indicating their value as a carbon-rich substrate. Seed germination tests on various species showed that hop-based coatings did not inhibit germination and in some cases improved it. Field trials confirmed that bean seeds coated with hops 24 h before sowing outperformed those coated with peat, particularly in integrated production systems, in terms of germination. The results of this study suggest a new area of research: using hop residues in sustainable seed treatments could promote the valorization of agricultural residues, while improving crop establishment and reducing the dependence on synthetic inputs. Full article

Garlic is a spice widely used worldwide, but ingestion of garlic can cause unpleasant breath odor that can be offensive in interpersonal interactions. Among several sulfur-containing components of garlic, allyl methyl sulfide is considered the primary causative agent of unpleasant garlic breath and body odor. We discovered that hop cone powder exhibits potent deodorizing activity against allyl methyl sulfide. Oxidation products of the hop bitter acids humulinone and hulupone were detected in a partially purified sample of hop cone powder. Oxidation products of the α-acids cohumulinone and n-humulinone showed approximately 10- and 15-fold stronger deodorizing activity than the parent α-acids, respectively. The deodorizing activity of oxidation products of β-acids was comparable to that of n-humulinone. It is presumed that the oxidation products of hop powder play an important role in the strong deodorizing activity of hop cone powder against allyl methyl sulfide. Full article

Hop by-products constitute a significant part of biomass in cones production for the brewing industry. The phenolic compounds (PCs) they contain can be used in the food and pharmaceutical industries but require qualitative and quantitative analysis. The aim of this study was to investigate the extent to which phenolic compounds profiles depend on cultivar, plant organ, and plant level. This paper shows for the first time that for hop, it is not only the plant organ that is important for PC content, but also the level from which it is obtained. Metabolites were investigated in cones, leaves, and stalks at three levels of the plant in Polish hop cultivars (Marynka, Lubelski, and Magnum). The PC content showed a differentiation due to the cultivar of hops, their anatomical part, and position in the plant (level), which reflects the degree of organ maturity. The total PC was the highest in leaves (up to 922 mg/100 g), while lower contents were found in cones (up to 421 mg/100 g) and stalks (up to 105 mg/100 g). The main PCs of leaves were kaempferol-3-glucoside (up to 328 mg/100 g) and rutin (up to 293 mg/100 g), while rutin dominated in cones (up to 209 mg/100 g). Full article

In the present study, the effect of two different formulations (NCH1 and NCH2) of trans-anethole was examined against hop flea beetles, Psylliodes attenuatus in field conditions. Products were applied in different locations in the spring seasons of 2019–2021. In 2019, 0.5% and 1% concentrations of both formulations were used so that the effective field dose could be determined. Doses of 1% for both formulations were shown to be more efficient. In 2020, experiments with this dose were carried out in two localities in order to select a more suitable formulation of the product (NCH1 vs. NCH2). The NCH1 formulation was shown to be more effective. After application, there was a significant reduction in the number of flea beetles compared to the control (p < 0.0001). On the other hand, no significant difference was found between the non-treated plot and the NCH2 formulation. In the third year of the experiment (2021), it was found that the number of P. attenuatus on plants treated with NCH1 encapsulation was significantly lower than in the untreated control (p < 0.0001). Residues of trans-anethole degraded immediately; thus, the product is suitable for use in the summer to protect the hop cones before harvest. Full article

Humulus lupulus L. (common hop) is a herbaceous plant whose female inflorescences, commonly called hop “cones”, are traditionally used in Bulgaria to prepare sourdough starters or “kvass”. Drawing from a review of historical and linguistic sources and ethnographic information collected by the authors, this study aims to define the traditional preparation of bread with hop sourdough, starting from the preparation of the hop cone decoction. Archival materials and early cookbooks attest to a rich tradition where hop-infused bread was valued for its distinctive flavor and preservative qualities. Fieldwork conducted in Bulgaria and among Bulgarian diasporas in Moldova provided insights into the continuity of these practices, underscoring the persistence of these traditional preparations despite modern industrial pressures. Ethnographic interviews and participant observations highlighted the ritualistic preparation of hop kvass and its role in community identity. The effect of hops on dough’s rheological properties and the quality features of bread were also reviewed. An increase in dough stability and resistance to elongation were generally reported, with a reduction in bread volume and porosity, especially with hop sourdough levels above 30%, but the incorporation of bioactive molecules was responsible for antioxidant, antimicrobial, and flavoring properties. Possible prospects for using hops in the food industry, based on the biological properties of this resource-rich plant, are outlined with a multidisciplinary approach. Full article

Bioactive phytochemicals, such as polyphenols, play vital roles in human health, but conventional extraction methods rely on hazardous solvents. This study establishes natural deep eutectic solvents (NADESs) as versatile and environmentally friendly alternatives for recovering a variety of bioactive compounds from plant materials. Five choline chloride-based NADESs were evaluated for their effectiveness in extracting betalains (from beetroot), carotenoids (from carrot and sweet potato), anthocyanins (from chokeberry pomace and red onion), and polyphenols (from Lonicera japonica flowers, hop cones, rowan berries, and spent coffee grounds). Notably, NADES2 outperformed water in betalain recovery (179.86 mg of betanin/100 g of beetroot), while NADES4 (choline chloride-urea, 1:2 molar ratio) matched the polyphenol extraction efficiency of ethanol. Using L. japonica flowers as a model for optimization, Response Surface Methodology (RSM) identified the solvent ratio and temperature as critical extraction parameters, using high ratios (12:1–15:1 v/w) and moderate heat (55–75 °C) to maximize recovery. NADES4 emerged as a high-performing solvent, achieving a total phenolic content (TPC) of 75.94 mg chlorogenic acid/g and antioxidant activity of 451.00 µmol Trolox/g under the following conditions: 60% aqueous dilution, 15:1 solvent ratio, and 80 °C, 30 min. These findings highlight NADESs as a green, tunable solvent system for phytochemical extraction across plant species, offering enhanced efficiency, reduced environmental impact, and alignment with sustainable practices. Full article

Biometric parameters of hop plants were studied over a three-year period on the Czech variety Premiant grown in the Žatec (Saaz) hop-growing region under an organic farming regime. Initially, only bine leaves developed, with lateral leaves emerging during the third growing month (June). Their leaf area at the time of harvest was larger than the bine leaves. The moment when the area size of both leaf categories was the same, designated as the breaking point (BP), was determined in the interval 181–195 DOY (day of year). The leaf area (LA) measured using infrared imaging and gravimetric methods yielded comparable results, with correlation coefficients of 0.93 and 0.96, respectively. The total leaf area of one hop plant (LA) with four trained bines, which developed dynamically during ontogeny, was 10.45 m² (2019), 6.65 m² (2020), and 12.04 m² (2021) in the harvest period. With a spacing of 3 m × 1 m, the corresponding Leaf Area Index (LAI) values were 3.5, 2.2 and 4.0 in the harvest season. Therefore, they are comparable to other crops such as maize or sorghum. Regression equations were calculated to determine the dry biomass of bine and lateral leaves depending on DOY. Correlations between the dry mass of leaves and the size of the leaf area for both bine and lateral leaves were also evaluated. This work also contains data on the mass proportions of the main plant organs (bine, leaves, cones). Full article

Hops are an essential raw material for beer production and the Czech Republic is not only a traditional hop grower but also participates in the breeding of varieties that are important on a global scale, mainly in terms of quality. The presented study deals with the evaluation of selected varieties grown in conventional and organic management over 4 years (2020–2023). The main contribution of this paper lies in the fact that remote sensing data of hop gardens were obtained by UAV during the growing seasons for four consecutive years and were subsequently used to explain the development of hop stands with respect to their yield and production quality. Hop fields were scanned using a UAV with a multispectral camera and the vegetation indices NDVI, GNDVI, NDRE, CIR and SAVI were derived. These indices were used as indirect indicators for determining vitality, health and structure for predicting yield and quality parameters (alpha acid content in hop cones). Based on statistical analysis it was concluded that in terms of yield assessment, spectral indices can explain hop yields up to 61%, with better results being achieved in the later stages of growth development. However, spectral indices are only able to explain a maximum of 18% of qualitative parameters. On the contrary, the maximum was reached in the early stages of stand development. UAV scanning monitors the canopies of hop stands with high resolution, similar to vineyards. Indices evaluating chlorophyll content appeared to be more suitable for affecting differences between hop stands. Full article

(1) Background: Over 90% of hop crops are currently used in beer production, with a small part used in the cosmetics and pharmaceutical industries. Spent hops as a waste product contain one of the strongest antioxidants, xanthohumol. The aim of the study was to purify spent hop extracts by magnetic dispersive extraction using iron oxide nanoparticles (IONP) to obtain pure xanthohumol; (2) Methods: The extract from the waste product obtained after supercritical carbon dioxide extraction of hops was prepared by ultrasound-assisted extraction utilizing different solvents, i.e., ethyl acetate, propanol, acetone, 80% methanol, ethyl acetate-methanol (1:1, v/v), and propanol-methanol (1:1, v/v). The hydrodynamic diameters and zeta potential of IONPs before and after incubation were measured by dynamic light scattering (DLS). The extracts were analyzed by reversed-phase high-performance liquid chromatography (HPLC). Isolated xanthohumol was identified based on the DAD spectrum in the range of 200–600 nm and by Fourier transform infrared spectroscopy/attenuated total reflectance (FT-IR/ATR); The antioxidant activity of extracts before and after incubation with IONPs was assessed using SNPAC (Silver Nanoparticle Antioxidant Capacity), DPPH (2,2-diphenyl-1-picrylhydrazyl radical), and FRAP (Ferric Reducing Antioxidant Power) assays, as well as total phenolic content (TPC) and total flavonoid content (TFC). (3) Results: The amount of added IONPs, the kind of solvent, and the contact time of the extract with nanoparticles were optimized. We found that 80% MeOH extract after incubation with IONPs (865 µg IONPs/g of spent hops) at room temperature for 48 h contains 74.61% of initial xanthohumol content, providing a final xanthohumol concentration of 43 µg mL⁻¹. (4) Conclusions: The proposed method of magnetic dispersive extraction using IONPs allows for the purification of spent hops extract and obtaining a pure product, namely xanthohumol, with a wide potential for practical applications in medicine, pharmacy, cosmetics, and agriculture. This is clear evidence of the usefulness of IONP as an effective sorbent. The method allows the use of residues from the brewing industry, i.e., the biomass of used hop cones to obtain a valuable substance. Full article

Dielectric elastomer actuators (DEAs) are increasingly recognized for their potential in robotic applications due to their ability to undergo significant deformation when subjected to an electric field. However, they are often limited by their low output power, which can make their integration into dynamic systems like hopping robots particularly challenging. This research optimizes the performance by introducing a cone DEA with a novel type of semi-diamond preload mechanism. This type of preload mechanism can meet the requirements of a negative-stiffness preload and a light weight. According to the experiments, the DEA can provide 3.62 mW power and its mass is only about 17.5 g. In order to drive hopping robots based on a cone DEA, this research introduces an energy accumulation mechanism coupled with a constant-torque cam for a hopping robot. The hopping robot weighs approximately 30.3 g and stands 10 cm tall in its upright position. Its energy accumulation mechanism involves a gear and cam transmission system, which is the key to store and release energy efficiently. The primary components of this mechanism include a torsion spring that stores mechanical energy when twisted, a constant-torque actuation cam that ensures the consistent application of torque during the energy storage phase, and a conical DEA that acts as an actuator. When the conical DEA is activated, it pushes a one-way clutch to the rocker, rotating the gear and cam mechanism and subsequently twisting the torsion spring to store energy. Upon release, the stored energy in the torsion spring is rapidly converted into kinetic energy, propelling the robot into the air. The experiments reveal that the designed DEA can drive the hopping robot by using the energy storage mechanism. Its hopping height is related to the pre-compression angle of the torsion spring. The DEA can drive the rigid hopping mechanism, and the maximum hopping height of the robot is up to 2.5 times its height. DEA hopping robots have obvious advantages, such as easy control, quietness and safety. Full article

Hops (Humulus lupulus L.) are widely recognized for their use in brewing, but they also possess significant pharmacological properties due to their rich bioactive compounds, with many varieties exhibiting diverse characteristics. This study investigates the chemical composition and biological activities of extracts from six hop varieties, focusing on quantifying xanthohumol and lupulone using High-Performance Liquid Chromatography (HPLC) and Total Phenolic Content (TPC) analysis. The hop varieties demonstrated significant variability in bioactive compound concentrations, with Aurora showing the highest xanthohumol (0.665 mg/g) and Zwiegniowski the highest lupulone (9.228 mg/g). TPC analysis revealed Aurora also had the highest phenolic content (22.47 mg GAE/g). Antioxidant activities were evaluated using DPPH, ABTS, CUPRAC, and FRAP assays, with Aurora and Oregon Fuggle displaying the most potent capacities. Aurora, in particular, showed the highest activity across multiple assays, including significant acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and tyrosinase inhibition, with IC₅₀ values of 24.39 mg/mL, 20.38 mg/mL, and 9.37 mg/mL, respectively. The chelating activity was also assessed, with Apolon demonstrating the strongest metal ion binding capacity (IC₅₀ = 1.04 mg/mL). Additionally, Aurora exhibited the most effective hyaluronidase inhibition (IC₅₀ = 10.27 mg/mL), highlighting its potential for anti-inflammatory applications. The results underscore the influence of genetic and environmental factors on the bioactive compound profiles of hop varieties and their biological activity offering promising avenues for pharmaceutical and nutraceutical applications. However, further studies are needed to fully understand the potential interactions between hop cones components. Full article

Background: Common hops (Humulus lupulus L.) play a key role in brewing, providing the bitterness, flavor, and aroma of beer, and are widely used in supplements for their antibacterial, anti-inflammatory, and antioxidant properties. However, despite their broad applications, the allergenic potential of common hops remains underexplored, particularly when compared to the closely related Humulus japonicus. This preliminary study aimed to investigate the allergenic potential of common hops and their potential cross-reactivity with common pollen allergens. Methods: The immunoreactivity of hop stalks, leaves, and cones was assessed using antibodies against major allergens from birch (Bet v1a), mugwort (Art v1), and timothy grass (Phl p5b), as well as three sera from pollen-allergic patients. Slot Blot analysis was performed using phosphate-buffered saline extracts from the stalks, leaves, and cones of three hop cultivars, while Western Blotting followed SDS-PAGE protein separation. Results: The results revealed significant immunoreactivity in native hop proteins, with diminished reactivity observed in denatured proteins. Cross-reactivity between hop proteins and major pollen allergens was confirmed, indicating that hop proteins may contribute to allergic sensitization in pollen-sensitive individuals. Conclusions: These findings underscore the potential allergenic risks associated with the consumption or exposure to hop-containing products. Full article