Hop cultivation vs. weather – an eternal theme

The course of weather conditions during the growing season, but also beyond it, decides the economics of hop cultivation every year. Ongoing climate changes manifested by more frequent occurrence of compound hot and dry waves affect hop cultivation not only in the Czech Republic, but in the entire region of Central Europe. The paper evaluates the harvest results (yields, alpha acid content) of four Czech hop varieties in the period 2019–2022 with a focus on the weather diametrically opposed vintages 2021 and 2022 on a specific agricultural farm in the Žatec (Saaz) hop-growing region. While the 2021 vintage was rich in precipitation in the decisive vegetation phase, the 2022 vintage was very dry and hot. The age of the plants significantly influenced the alpha acid content of the varieties Saaz, Sládek and Premiant independently of the vintage. Young growths of the Saaz variety contained at least 60% rel. more alpha acids than older growths (more than 5 years old), while the increase in the Sládek variety was 30–40% rel. and in the Premiant variety 20–25% rel. In the case of the variety Agnus, the age of the plants did not have a demonstrable effect on the content of alpha acids. In 2021 the yields of all varieties were negatively affected by the calamitous occurrence of downy mildew. In 2022, the rainfall deficit was so large that it could not be fully compensated even by the maximum use of drip irrigation. Of the evaluated varieties, the Agnus variety coped best with the different weather conditions of the assessed vintages. This shows that the cultivation of climate resistant varieties is one of the promising but time-consuming ways to face the expected climate changes. Other options include regular renewal of hop growths, consistent regionalization, i.e. planting hop in locations that are suitable for the given variety and efficient use of irrigation systems

První český chmel v kvalitě bio

Historie organického pěstování chmele ve světě začala v polovině 80. let minulého století v Bavorsku. V roce 2011 se organickému pěstování chmele věnovalo 55 farem v deseti zemích světa. Obdělávají celkem 187 ha chmelnic s roční produkcí 240 t certifikovaného biochmele

Methods for verifying the authenticity of hops – an effective tool against falsification

Falsifi cation attempts occur in almost all commodities and hops is no exception. It is therefore necessary to look for ways to verify its authenticity. This review summarizes modern methods for verifying the authenticity of hops and also provides the latest results of the collaboration of the Research Institute of Brewing and Malting, PLC. and the Hop Research Institute, Ltd., in Žatec. Chemotaxonomic and genetic methods are used to verify the authenticity of hops. Chemical analyzes of newly bred hybrids potentially suitable for Czech beer focused on the content and composition of alpha and beta acids, content and composition of hop oils, and content of total polyphenols were performed and molecular genetic analyses of 150 selected hop genotypes including a world-wide range and breeding material were conducted in 2015. These data were used to construct a comprehensive dendrogram from the tested genotypes. The authors also examined the profi ling of Czech hop varieties based on the chemical profi les of proanthocyanidins, and succeeded in using cluster analysis to clearly distinguish the varieties of hops including their genetic relatedness

Kazbek – The First Czech Aroma “Flavor Hops” Variety: Characteristics and Utilization

The world market of craft beer, especially dry hopped beers, has been constantly growing in the last few years. That is why new varieties of hops are still being bred. This article gives the genetic, agronomic, chemotaxonomic and brewing characteristics of Kazbek, the first “flavor hops” variety bred in the Czech Republic. Kazbek genetically belongs to a group of bitter American hops resulting from Brewers Gold variety, but the alpha acids content is relatively low, 5.0–8.0% by weight. The content of a homologous series of geranyl esters (acetate – propionate – isobutyrate) in an amount 2–4% of total essential oils (1–1.5 g/100g) is considered to be the originator of the specific, mainly citrus-like aroma of Kazbek. Moreover, the essential oil fraction contains about 25 sulfurous substances, predominantly thioesters. In the pilot scale brewing tests, the quality of Kazbek hops was proved both in kettle and dry hopping of Pilsner lagers. The overall sensory impression of kettle hopped lagers was comparable to Saaz hops, the differences were in the character of hop-derived flavor and bitterness. The best results of dry hopped beers were achieved for a 2.5 g/l hop dose and a contact time of 3 days

The effect of copper fungicides on the rate of photosynthesis and the transpiration of hop plants

The paper evaluates the effect of copper fungicide spraying on the rate of photosynthesis and transpiration of hops, the influence of spraying on the elemental copper content in the leaves and cones hop variety Agnus. Photosynthetic rate was measured by LC pro+ (infrared analyzer) in the Hop Research Institute Saaz in the field in some periods of 2008, 2009 and 2010. Dry cones and leaf samples (taken before and after application of copper fungicides) were analyzed in an accredited laboratory for elemental copper

Determination of Bitter Compounds in Hops – Effect of Crop Year and Hops Age

Our study is focused on mutual comparison of four methods of determination of alpha acids in hops (EBC 7.4, EBC 7.5, ČSN and EBC 7.7) and their application in evaluation of hops stored under different conditions. Furthermore, the results of the comparison of predicted and actual alpha acid values in the long-term monitoring of harvesting of three Czech hop varieties are discussed. The largest differences were found between the EBC 7.5 (LCV) and EBC 7.7 (HPLC) methods; the first method gives systematically higher results and the difference exponentially increases with the hop storage index (HIS) value. The difference in HSI in fresh hops is 10 – 15% rel. while the difference in older hops with HSI 0.6 – 0.7 is 25 – 45% rel. Pre-harvest prognosis and harvest estimate of alpha acids in the Saaz variety are in good agreement with the facts (kr = 0.93, kr = 0.95) and the same holds for the harvest estimation relation and the reality of the varieties Sládek and Premiant (kr = 0.93; 0.97)

Classification of Czech Hops According to their Contents of Prenylflavonoids

The prenylated flavonoids are hop components with the most beneficial health effects. Information about their content and the dynamics of their decrease during hops processing is necessary for the production of beer with an increased content of these substances. This study deals with the long-term monitoring of the prenylflavonoids and α-bitter acids contents and their ratios in the whole spectrum of domestic hop varieties as well as with changes in these parameters during storage and hop processing. It was confirmed that the newly cultivated Agnus and Vital varieties are the varieties with the highest contents of prenylated flavonoids. As a result, the Vital variety is particularly useful in non-brewing applications. Based on the monitoring of the decrease in the levels of these components during hop processing it was recognised that development of new gentler methods, particularly for the hop drying would be necessary. These methods should minimize the risk of thermal and oxidative degradation

Perinatal and 2-year neurodevelopmental outcome in late preterm fetal compromise: the TRUFFLE 2 randomised trial protocol

Introduction: Following the detection of fetal growth restriction, there is no consensus about the criteria that should trigger delivery in the late preterm period. The consequences of inappropriate early or late delivery are potentially important yet practice varies widely around the world, with abnormal findings from fetal heart rate monitoring invariably leading to delivery. Indices derived from fetal cerebral Doppler examination may guide such decisions although there are few studies in this area. We propose a randomised, controlled trial to establish the optimum method of timing delivery between 32 weeks and 36 weeks 6 days of gestation. We hypothesise that delivery on evidence of cerebral blood flow redistribution reduces a composite of perinatal poor outcome, death and short-term hypoxia-related morbidity, with no worsening of neurodevelopmental outcome at 2 years. Methods and analysis: Women with non-anomalous singleton pregnancies 32+0 to 36+6 weeks of gestation in whom the estimated fetal weight or abdominal circumference is <10th percentile or has decreased by 50 percentiles since 18-32 weeks will be included for observational data collection. Participants will be randomised if cerebral blood flow redistribution is identified, based on umbilical to middle cerebral artery pulsatility index ratio values. Computerised cardiotocography (cCTG) must show normal fetal heart rate short term variation (≥4.5 msec) and absence of decelerations at randomisation. Randomisation will be 1:1 to immediate delivery or delayed delivery (based on cCTG abnormalities or other worsening fetal condition). The primary outcome is poor condition at birth and/or fetal or neonatal death and/or major neonatal morbidity, the secondary non-inferiority outcome is 2-year infant general health and neurodevelopmental outcome based on the Parent Report of Children's Abilities-Revised questionnaire. Ethics and dissemination: The Study Coordination Centre has obtained approval from London-Riverside Research Ethics Committee (REC) and Health Regulatory Authority (HRA). Publication will be in line with NIHR Open Access policy. Trial registration number: Main sponsor: Imperial College London, Reference: 19QC5491. Funders: NIHR HTA, Reference: 127 976. Study coordination centre: Imperial College Healthcare NHS Trust, Du Cane Road, London, W12 0HS with Centre for Trials Research, College of Biomedical & Life Sciences, Cardiff University. IRAS Project ID: 266 400. REC reference: 20/LO/0031. ISRCTN registry: 76 016 200

Evaluation of hop quality

Kvalita chmele je posuzována v několika úrovních od sklizně přes zpracování až po dodávku zpracovaného chmele zákazníkům, kterými jsou ponejvíce domácí a zahraniční pivovary. V metodice jsou popsány nejdůležitější analytické metody, používané k hodnocení kvality chmele, uvedeny jejich přednosti, nedostatky a omezení. Důraz je kladen zejména na stanovení obsahu alfa kyselin, nejdůležitějšího kvalitativního parametru chmele, který lze stanovit několika způsoby s odlišným výsledkem. Důležitou součástí je pojednání o nežádoucích a cizorodých látkách ve chmelu, jejichž obsah je mnohdy limitujícím faktorem prodeje. Na základě výsledků chemických analýz lze s vysokou pravděpodobností určit identitu odrůdy a stupeň stárnutí chmele, ke kterému při skladování a zpracování zákonitě dochází

Hop beta acids: Properties, significance and utilization.

Hop beta acids, the vital components of hop resins, are important on three levels - brewer, antimicrobial, and physiological. In the brewing industry, low solubility in aqueous solutions and the ability to oxidation into more soluble products is the defining characteristic of beta acids. Oxidation occurs in the course of processing and storage of hops and to a small extent also during beer production. Beers hopped by preoxidized beta acids have strong sensory bitterness. The bittering yield of oxidation products of hop beta acids is approximately 35-40% of the iso-alpha acids' bitterness intensity. A wide range of evidence of the biological and pharmacological effects of hop bitter acids, especially the effects of beta acids has been collected. Hop acids are potential sources of treatment or prevention of many diseases, including cancer, diabetes, osteoporosis, cardiovascular diseases, inflammatory and metabolic disorders. In addition, the antimicrobial effects of beta acids against different microorganisms are significant and have been utilized in sugar production, distilling and livestock sectors. This paper summarizes the current knowledge about the role beta acids play in the brewing process, and focuses on their bioactive effects.Hop beta acids, the vital components of hop resins, are important on three levels - brewer, antimicrobial, and physiological. In the brewing industry, low solubility in aqueous solutions and the ability to oxidation into more soluble products is the defining characteristic of beta acids. Oxidation occurs in the course of processing and storage of hops and to a small extent also during beer production. Beers hopped by preoxidized beta acids have strong sensory bitterness. The bittering yield of oxidation products of hop beta acids is approximately 35-40% of the iso-alpha acids' bitterness intensity. A wide range of evidence of the biological and pharmacological effects of hop bitter acids, especially the effects of beta acids has been collected. Hop acids are potential sources of treatment or prevention of many diseases, including cancer, diabetes, osteoporosis, cardiovascular diseases, inflammatory and metabolic disorders. In addition, the antimicrobial effects of beta acids against different microorganisms are significant and have been utilized in sugar production, distilling and livestock sectors. This paper summarizes the current knowledge about the role beta acids play in the brewing process, and focuses on their bioactive effects