Alpha Acids Content in Czech Hops from the 2025 Harvest - Forecasts, Reality and Trends

It has been well established that beer is an excellent source of polyphenols, due in part to the contribution of xanthohumol and other compounds from hops. The intent of this study was to explore the relationship between alpha acid content, antioxidant activity, and boil time in hops. Ten hops strains with different alpha acid contents were analyzed for phenolic antioxidant content via Total Phenolic Concentration (TPC) and Ferric Reducing Antioxidant Power (FRAP) assays. Each strain was boiled for 10, 30, or 60 min, consistent with typical beer brewing protocols. Phenolic and antioxidant content increased with boil time, with Citra hops showing higher phenolic content than other strains regardless of boil time. It appears that longer boil times yield higher TPC and FRAP concentrations regardless of alpha acid content. There was a nonstatistical inverse correlation between alpha acid and phenolic content; as a result, beers that use high alpha acid hops or short boil times may have lower TPC and FRAP concentration than beers that use low alpha acid hops and long boil times.

Between 2009 and 2023, European hop varieties were evaluated within genetic resources in the Czech Republic. The objective of this paper was to determine the variability of hop alpha and beta acid contents in the monitored varieties at a single site over the period of fifteen years. At the same time, the trend in which the observed substances decrease or increase was assessed. The lowest average alpha acid content was detected in Strisselspalter (2.96% w/w), while the highest content was found in Herkules (14.03% w/w). The lowest variability in alpha acid content was measured in Vital (14.59%) and Herkules (16.48%). Unlike the aforementioned varieties, Golding exhibits the highest variability (46.28%). All varieties showed a decreasing trend in alpha acid content over the fifteen years of cultivation. Lubelski had the highest decrease in alpha acid content and also showed a high correlation (r² = 0.664). The varieties with the lowest average beta acid content were Celeia (2.77% w/w) and Golding (2.97% w/w). The variety with the highest average beta acid content was Vital (7.30% w/w). All varieties displaied a decreasing trend in beta acid content. Perle had the lowest trend of decrease in beta acid content, while Tradition had the highest trend of decrease. The varieties Strisselspalter, Saaz, Tettnang, Sládek, and Bobek had an alpha/beta acid ratio below 1. However, the variety Bobek showed the highest variability at 32.18%. Herkules had the highest alpha/beta acid ratio (3.20). The most stable alpha/beta acid ratio was found in Marynka (8.41%).

Since 2017, a field experiment has been conducted in a dry area with 11 Czech hop varieties. The highest yields were achieved by the Uran variety (2.83 t/ha) and Saaz Shine variety (2.76 t/ha), which also exhibited the lowest yield variability, at 11.17% (Saaz Shine) and 12.53% (Uran). The lowest hop yield was recorded by the Harmonie variety (1.17 t/ha), which also showed high yield variability (30.92%). The Bohemie variety had the highest yield variability of hops at 35.26%. While the Gaia (14.66% w/w) and Uran (13.53% w/w) varieties had the highest alpha acid content. Conversely, the Mimosa variety showed the lowest alpha acid content (1.56% w/w) and also the lowest alpha/beta acid ratio (0.29). The Rubín variety reached the highest alpha/beta acid ratio (3.00). The Uran variety exhibited the lowest variability in alpha (6.16%) and beta (6.28%) acid content. In contrast, the Harmonie variety had the highest variability in alpha (59.02%) and beta (38.18%) acid content. The Uran and Saaz Shine varieties are the most suitable for the dry area. Additionally, the Gaia and Saaz Brilliant varieties showed good performance parameters. The hop varieties Vital, Gaia, Saaz Brilliant, and Saaz Shine had the most intense hop aroma, while the Boomerang and Uran varieties had a high intensity of spicy aroma.

. In Ukraine, hops are basically processed into Type 90 pellets, that are practically indistinguishable in terms of biochemical indicators from hop cones. Pellets of hop are the single domestic source of hop products that can be serve as an alternative to imported pellets and extracts that used in the Ukraine brewing. Comprehensive studies of the evaluation of Type 90 hop pellets of aromatic and bitter varieties produced in Ukraine and European countries allowed establishing that they have different biochemical compositions and consequently, different brewing value. That have been identified differences in the absolute values of indicators such as the mass fraction of alpha acids, beta acids and their composition, xanthohumol, essential oil, the ratio of valuable hop compounds: beta acids to alpha acids and components of the essential oil. It has been determined that in hop pellets of aromatic varieties, the content of alpha acids changing from 3.3% in the Klone 18 variety to 5.9% in the Hallertauer Tradition variety. The content of beta acids, in the investigated pellets, ranges from 3.6% (Klone 18) to 6.7% in the Slavyanka variety. It is established that the hop pellets made from Ukrainian varieties Zagrava and Slavyanka have significantly higher content of beta acid 6.3% and 6.7%, respectively, compared to pellets of foreign varieties. There is a significant advantage in the resin fraction of beta acids over the fraction of alpha acids in the pellets of Slavyanka, Klone 18, Zhatetsky and Zagrava varieties, that they meaning retain a positive coefficient of aromaticity between the content of beta and alpha acids that ranges from 1.18 to 1.37. The content of alpha acids ranges from 8.7% in the Polisky variety to 14.1% in the Magnum variety in the hop pellets of bitter varieties. The content of beta acids in the same pellets ranges from 4.2% to 5.9%. It has been established that the composition of alpha and beta acids in the investigated pellets changes depending on the variety. It has been proven that Ukrainian-produced hop pellets correspond to their international counterparts in terms of their characteristics. Specifically, the biochemical and technological indicators of Klone 18 hop pellets correspond to the characteristics of pellets of the Czech variety Zhatetsky, pellets made from the bitter variety Alta correspond to the biochemical indicators of German Magnum pellets but pellets of varieties such as Slavyanka and Zagrava exceed the world analogies in terms of the composition and quality of bitter substances and essential oil. Based on the comparative biochemical characteristics of Type 90 hop pellets of Ukrainian and European production, the quality of Ukrainian hop products has been found to be at a global level. Certified domestic hop products, specifically Type 90 pellets, can be used do not only by Ukrainian brewers but also by other manufacturers to create new innovative and competitive products with various functional purposes.

Goal. To determine the brewing quality of hop granules of type 90 of Ukrainian production and to establish their competitiveness based on biochemical and technological assessments. Methods. Physico-chemical — to determine the quality indicators of hop granules, special and generally accepted in the hop industry, mathematical-statistical and methods of the European Brewing Convention, in particular, high-performance liquid chromatography, capillary gas chromatography, conductometry, spectrophotometry. Results. Biochemical evaluation of hop granules of type 90 of Ukrainian varieties Klon 18, Zlato Polissia, and Alta by the amount and composition of bitter substances, essential oil is given and their comparison with foreign granules of varieties Zhatetskyi (Czech Republic) and Magnum (Germany) is carried out. It was noted that the content of alpha acids in hop granules of aromatic varieties varied from 3.7% in the Klon 18 variety to 4.5% in the Zhatetskyi variety. The content of beta acids in the investigated granules ranged from 4.4% (Zlato Polissia) to 6% in the granules of the Zhatetskyi variety. The proportion of beta acids in the resins of the Klon 18, Zlato Polissia, and Zhatetskyi granules was significantly higher than the proportion of alpha acids, i.e. they retained a positive aromaticity ratio between the content of beta and alpha acids, which was 1.16–1.30. In the granules of fine aromatic varieties, the content of cohumulone was 24.6–26.0%. In hop granules of bitter varieties, the content of alpha acids varied from 9.7% in the Alta variety to 16.0% in the Magnum variety. The content of beta acids in these same granules ranged from 5.5% in the Alta variety to 7% in the Magnum variety. The content of cohumulone varied in the range from 23.5% in the granules of the Alta variety to 29% in the granules of the Magnum variety. It was proven that Ukrainian-made hop granules corresponded to world analogs in terms of their characteristics. Conclusions. It was established that the analyzed hop granules of type 90 of Ukrainian production were not inferior in quality to foreign granules and had the prospect of wide use in brewing, ensuring high-quality beer.

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.

With the development of new trends in healthy eating, for consumer satisfaction, with aim to expand the range of bakery products and enrich bread with biologically active compounds of hops, bread production with the addition of cones of this unique plant in terms of bitter and polyphenolic substances, aromatic and essential oils has become widespread. The research conducted to study and substantiate the effective utilization of a complex of technologically valuable substances of Ukrainian fine aromatic hops of the Perlyna variety allowed to establish the possibility and feasibility of its application in baking and its impact on bread quality. The analysis of the results showed that the bittering qualities of hops had a significant impact on the taste of bread. In contrast, polyphenolic substances had a lesser effect on the taste, but in combination with bitter substances, they significantly affect consumer qualities. The results of studies of the application of sourdough starter of Perlyna aromatic hop with different content of alpha acids and polyphenolic substances showed that the bread had high taste qualities when added to the 1 kg of flour: 23.9 to 35.8 mg of bitter substances and 45.2 to 72.1 mg of polyphenolic substances. With lower amounts of bitter substances and higher amounts of polyphenols, the taste of the bread was almost the same as the control sample, although the physicochemical parameters improved. With an increase from 35.8 to 43.4 mg of bitter substances, a subtle bitterness was felt against the background of a pleasant hop aroma. Adding more than 50.8 mg of bitter substances to the 1 kg of flour made the bread noticeably bitter. Based on the example of the Pearl hop variety, the dosage of hop expenses was optimized and the calculation of the rate in baking was proposed, taking into account the content of bitter alpha acids in it. The optimally justified rate of bitter substances of hops to ensure excellent taste and consumer properties of bread is the range of added alpha acids from 23.9 to 43.4 mg per 1 kg of flour. The proposed technology has improved the consumer properties and taste of bakery products by imparting a hop aroma and a stable optimally normalized bread taste with a light, delicate bitterness. At the same time, the volume of bread, porosity, porosity structure and elasticity of the crumb are increased. Reducing the amount of yeast did not affect the fermentation of the dough and the stability of the shape of the final product. This will contribute to the health and preventive effects of the products.

Significant influence of weather conditions on alpha acid contents in hop cones is generally accepted. Long-term monitoring of alpha acid content in hops cultivated in the region of central Europe shows notable year to year differences. Mathematical models of the relationship between alpha acid content and meteorological parameters were worked out for 'Saaz' aroma variety using data covering the years 1981-2006. Mean alpha acid content was determined by lead conductance method (EBC 7.4, toluol). Meteorological data were provided with CHMI (Czech Hydrometeorological Institute) observatory in Doksany located approximately 2 km from the farm. Using multi-linear regression, a ten parameter model has been outlined. Average temperatures from July and August, average air humidity from June, July and August, average daily sunshine duration from June, July and August and accumulated precipitation from August have been found as key input variables of the model. Correlation coefficient of the relationship between predicted and actual alpha acid contents is r=0.914, coefficient of determinancy r 2 =0.835. The model showes that alpha acid content in 'Saaz' aroma hops is influenced by weather conditions in a relatively short time period June-August, i.e. stage of flowering, cone forming and ripening. July temperatures are the most significant weather parameter (r i =-0,24) effecting alpha acid contents in 'Saaz' hops confirming empiric experience.

SummaryThe effect of Hop latent virus (HpLV), Hop mosaic virus (HpMV), and Prunus necrotic ring spot virus [PNRSV (apple, A, and intermediate, I, serotypes)], on the survival of softwood cuttings, the vigour (height) of early season growth, cone yield, and the levels of brewing organic acids in mature plants, was assessed in four hop (Humulus lupulus) cultivars in Tasmania, Australia. Virus infections were associated with an increase in the mortality of softwood cuttings following propagation. In all cultivars, height of early growth was a poor indicator of the effect of viruses on cone yield and levels of brewing organic acids (alpha and beta acids). In cv. ‘Nugget’, infection by the virus combinations studied was not associated with reductions in cone yield, however plants infected by PNRSV‐I, in 2000, had 11% lower alpha acids and 7% lower beta acids. In ‘Opal’, infection by HpLV and HpMV were the most deleterious to cone yield, however the effect of HpMV was ameliorated when in combination with PNRSV‐I. Reductions in alpha and beta acid content were attributable only to mixed infections of HpLV + HpMV in combination with either serotype of PNRSV. In ‘Pride of Ringwood’, yield loss was mostly attributable to HpMV and to a lesser extent, HpLV. Some ameliorations in cone yield loss occurred in plants containing a mixed infection between HpMV and HpLV or either of the ilarvirus serotypes. Both of the ilarviruses and HpMV caused reductions in alpha acid content. In ‘Victoria’, cone yield loss was mostly attributable to combinations of viruses such as HpLV + PNRSV‐I and HpLV + HpMV. The deleterious effect of HpLV + HpMV was ameliorated by PNRSV‐A and to a lesser extent, PNRSV‐I. Infection by the virus combinations studied did not significantly affect alpha and beta acid levels in either year. Results suggested the effect of viruses and their combinations differed between cultivars and varied between seasons. This information, when combined with knowledge of the rates of virus re‐infection, can be used to recommend control strategies for the Australian hop industry.

From the brewing and commercial point of view, the content of alpha acids is the most important quality parameter of hops, which is subject to significant annual fluctuations. The established system for evaluating the content of alpha acids in Czech hops consists of pre-harvest and harvest predictions and a detailed analysis of reality based on the analysis of all purchasing lots of raw hops. It is differentiated according to varieties and hop growing areas. This article presents the results of the 2022 harvest, discusses the influence of weather conditions, the age of hop gardens and virus-free seedlings on the harvest results, and the relationship of predictions to reality. The average content of alpha acids in the majority Saaz variety in the Saaz, Auscha and Tirschitz hop growing regions was 2.88, 2.80 and 2.63% by weight in the original respectively. In all areas, the alpha acid content has been significantly affected by the age of the hop growths. Hybrid varieties coped with adverse weather conditions much better than most aromatic hops. The total production of alpha acids in Czech hops from the harvest of 2022 was 182.9 tons, one of the lowest in the last 15 years. It is due to the concurrence of two factors: the low yield per hectare and the content of alpha acids in Saaz hops. The cause was, similarly to Germany, an extreme deficit of precipitation and high temperatures during the vegetation season.

The article presents the results of breeding work for the creation of new high-yielding varieties of bitter-aromatic hops with a high content of alpha-acids carried out in 2004-2020 in the Chuvash Republic on gray forest soils. The work was done by individual clonal selection of the best hop plants from the collection nursery. Seven high-yielding breeding numbers with a high alpha-acid content were selected from the collection nursery. After passing through all the stages of study in each of the appropriate nurseries from seven numbers, two clones were selected to create new varieties. Data were obtained on the parameters of the initial clonal breeding material, depending on weather conditions and the age of plantings. The selected clones (1-17 bitter-aromatic type and 6-26 bitter type) correspond to the specified indicators: collection of raw hops is not less than 4.0 kg from a bush, the duration of the growing period is 100-120 days, the content of alpha acids is not less than 5.0 %. Documentation on clone 1-17 was sent to the State Variety Commission for registration of a new variety Salampi. The variety is characterized by stable performance and quality indicators. The productivity of the variety is 30.0 c/ha (4.0 kg/bush) with a content of alphaacids of 9.3 %. The Podvyazny standard variety has 26.4 c/ha (3.5 kg/bush), the content of alpha-acids is 8.8 %. Testing of clone 6-26 will be continued to obtain complete and objective data.

Czech hop varieties are evaluated as part of maintenance breeding. Every year, this evaluation includes ten mother plants of each hop variety. Yield is determined in kilograms of fresh hops per plant. The t-test is used to determine significance. Results from the years 2014–2019 show that Gaia and Kazbek have the highest yield (3.17 kg/plant and 3.05 kg/plant, respectively). Their yield is higher than that of the Harmonie, Agnus, Bohemie, Premiant, Sládek, Boomerang and Saaz varieties. Saaz has the lowest hop yield, i.e. 1.85 kg/plant. Bor, Saaz Late, Saaz and Sládek show the lowest variability, which ranges between 20.56 and 20.58%. Gaia has the highest variability (34.33%). Gaia also has the highest alpha acid content (12.30%) with a probability of 95% to 99%. Vital and Boomerang have a higher alpha acid content than other Czech hop varieties (11.09% and 10.81%, respectively) with a probability of 99%. Saaz Late (3.42%) and Saaz (3.06%) have the lowest alpha acid content with a probability of 95% to 99%. The variability of alpha acid content is considerably lower than the hop yield variability. Rubín has the lowest year-on-year variability of all Czech varieties (4.81%). Vital and Gaia have a very low variability (5.63% and 5.72%, respectively). A higher variability of alpha acid content was found in Saaz Late, Premiant, Agnus, Saaz, Kazbek, Bor and Harmonie, ranging between 8.01% and 10.21%.

The stability of the agricultural and technological properties of hop varieties over the course of time and under changing climate is essential for both growers and brewers. This study is a typical case of monitoring 12 hop varieties selected from a collection of hop genetic resources, that were evaluated in the years 2009 to 2021. The assessed parameters were the hop yield and content of alpha acids with a focus on the variability/stability of this characteristics. Only the Pilgrim and Target hop varieties from England showed exceptional hop yield above 3 kg/plant. On the other hand, the lowest hop yield was obtained from the Saaz and Bramling Cross hop varieties, i.e. below 1.5 kg/plant. The lowest variability of hop yield – below 30% – was found in the Savinjski Golding, Bramling Cross and Saaz hop varieties. In contrast, the Bobek, Aurora, Pioneer and Phoenix hop varieties demonstrated the highest variability of hop yield, i.e. above 50%. Further, also Target and Phoenix have the highest content of alpha acids, namely 9.68% w/w and 9.56% w/w, respectively. The lowest content of alpha acids was determined in Saaz, which was the only hop variety with an alpha acid content below 3.0% w/w. The Premiant, Target and Aurora hop varieties exhibited a variability of alpha acid content below 20%. On the contrary, the Bobek and Pilgrim hop varieties had the highest variability of alpha acid content, namely above 30%.

From the brewing and commercial point of view, the content of alpha acids is one of the most important quality parameter of hops, which is subject to significant annual fluctuations. The established system for evaluating the content of alpha acids in Czech hops consists of pre-harvest and harvest predictions and a detailed analysis of reality based on the analysis of all purchasing lots of raw hops. It is differentiated according to varieties and hop growing areas. This article presents the results of the 2021 harvest, discusses the influence of weather conditions, the age of hop gardens and virus-free seedlings on the harvest results, and the relationship of predictions to reality. The average content of alpha acids in the majority Saaz variety in the Žatec, Úštěk and Tršice areas was 4.45, 4.20 and 3.36% by weight in the original respectively. In all areas, the alpha acids content has been significantly affected by the age of the hop growths. The total production of alpha acids in hops harvested in the Czech Republic in 2021 was 414.5 tons. The harvest is the highest in the last 25 years; the result is due to the combination of two factors, both high yield per hectare and high alpha acids content.

The article covers information on the preliminary results of breeding work carried out in the Chuvash Republic in 2002-2017 on production of new high-yielding hops varieties of bitter and aromatic types with high content of alpha acids. The basis of clonal selection method is the production of stable over time introduced population characterized by a high level of polymorphism in the main economically important traits. The method of clonal selection of hops, as a vegetative propagated culture, allows to select plants with tending to positive indicators in a population of one variety or a mixed variety and to fix these characteristics in the progeny in the course of further work. From the high-yielding varieties with high content of alpha acids selected in the collection 7 hops varieties were chosen for further work. Depending on the weather conditions and age of plantings preliminary data on the parameters of the basic clonal selection material were obtained. Two clones with the following parameters were selected. Clone 1-17 of bitter-aromatic type, growing season length is 100 days, the wet hop yield is 4.1 kg per a plant, the content of alpha acids in cones is 9.5%. Clone 6-26 of bitter type, growing season length is 112 days, the wet hop yield is 4.3 kg per a plant, the content of alpha acids in cones is 9.5%.