Hop Research Institute

Žatec, Czech Republic

Hop Research Institute

Žatec, Czech Republic
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Pokorny J.,Hop Research Institute | Krivanek J.,Hop Research Institute | Jezek J.,Hop Research Institute | Pulkrabek J.,Czech University of Life Sciences
Acta Horticulturae | Year: 2013

The paper evaluated changes in the rate of photosynthesis, transpiration and chlorophyll content during the hop growing season. The device LC pro+ (portable infrared gas analyzer) and Chlorophyll spacemeter SPAD-502 was used for the measurement of physiological processes. The generic model of the photosynthetic rate was defined in relation to the growth phase of the hop during the growing season. The results of measuring of photosynthetic rate (2007 to 2009) showed that photosynthesis gradually increased during the rapid growth and photosynthetic activity increased in the flowering stage of hop plants. On the contrary, hop plants reduced assimilation as the hop cones matured. A similar trend was found for measurement of chlorophyll in the leaves. The transpiration rate decreased with the course of hop plant ontogeny. The average rate of photosynthesis during the growth season in 2007 to 2009 ranged from 5.61 to 7.82 αmol CO2.m-2.s-1. The average transpiration rate ranged from 1.02 to 1.21 mmol H2O.m-2.s-1. The average values of chlorophyll ranged from 36.78 to 44.07.

Mikyska A.,Research Institute of Brewing and Malting | Krofta K.,Hop Research Institute | Haskova D.,Research Institute of Brewing and Malting | Culik J.,Research Institute of Brewing and Malting | Cejka P.,Research Institute of Brewing and Malting
Journal of the Institute of Brewing | Year: 2011

Improving beer flavour stability is an important brewing goal. Pilot scale brewing trials (50 L) were performed that focused on the determination of the influence of hop pellet dosage and dosage timing on carbonyl compounds in stored beer. The reducing activity of experimental worts, beers and stored beers appeared to depend on the hop pellet dose. Brews with lower amounts of hop antioxidants showed an enhanced formation of carbonyl compounds over the course of beer storage. A correlation between DPPH reducing activity and the content of some carbonyls, including the important markers 2-furfural and (E)-2-nonenal, was found. Fresh and aged beers hopped by different amounts of hop pellet doses were clearly distinguishable according to their carbonyl content using Cluster analysis. Results of the sensorial analysis corresponded to the analytical criteria values. Results of this study bring further evidence of the indispensable impact of hop antioxidants on the suppression of undesirable carbonyl compound formation in the course of beer staling, which can be significant in beers hopped by aroma hops. However, hop antioxidants are only one of many factors affecting beer staling. © 2011 The Institute of Brewing & Distilling.

Mikyska A.,Research Institute of Brewing and Malting | Krofta K.,Hop Research Institute
Journal of the Institute of Brewing | Year: 2012

Changes in the content and composition of hop secondary metabolites during storage are reflected in beer quality and in the economics of beer production. A 12-month storage experiment with T90 pellets of four hop varieties showed different dynamics of hop aging in relation to both storage conditions and hop variety. Negligible effects on the α- and β-acids were detected during storage without air access at +2°C. Storage at +20°C resulted in a final loss of 20-25% α-acids, but the content of β-acids did not change significantly. Large decreases in α-acids (64-88%) and in β-acids (51-83%) were found in hops stored with access to air at +20°C. The rate of decline accelerated markedly after 6 months of storage. In terms of hop resin changes, Premiant and Sládek 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 after 6 months. The DPPH (1,1-diphenyl-2-picrylhydrazyl) antiradical potential decrease was significant only in hops stored under aerobic conditions. The depletion was 9-25% after 1 year; Saaz was the most stable variety. © 2012 The Institute of Brewing & Distilling.

Pavlovic V.,University of Maribor | Pavlovic M.,University of Maribor | Pavlovic M.,Slovenian Institute for Hop Research and Brewing | Cerenak A.,Slovenian Institute for Hop Research and Brewing | And 7 more authors.
Plant, Soil and Environment | Year: 2012

The paper analyses the influence of four main weather parameters on alpha-acid contents for the main hop variety Aurora (Super Styrian Aurora) in Slovenian production for the time period 1994-2009. Through inspection of correlation coefficients, it tries to find specific times of the year when the weather conditions affect the alpha-acid content with a view to prediction in Slovenia. The most significant time periods of weather that influenced the alpha-acid contents of the Aurora variety during the growing season are identified as attributes of temperatures calculated from the interval from 25 th to 30 th week (T 2530, r = -0.88, P < 0.01), as attributes of rainfall and sunshine from the interval from 25 th to 29 th week (R 2529, r = 0.85, P < 0.01 and S 2529, r = -0.75, P < 0.01) and attributes of relative humidity from the interval from 27th to 32nd week (RH 2732, r = 0.71, P < 0.01). The attribute T 2530 represents the sum of active temperatures from June 18 to July 29 of that year. Similarly, the attribute R 2529 corresponds to the rainfall (in mm or L/m 2) that fell during the June 18 to July 22 etc.

Jupa R.,Masaryk University | Balaz M.,Masaryk University | Svoboda P.,Hop Research Institute | Gloser V.,Masaryk University
Plant, Soil and Environment | Year: 2013

Intervarietal differences in xylem structure could significantly affect water transport as well as vulnerability to cavitations and thus crop yield. Evaluation of crop varieties with respect to the specific traits can be thus helpful in breeding and agricultural practice. In the present study we compared basic anatomical traits (vessel length and diameter) as well as theoretical and measured hydraulic conductivities (K) of xylem in stems of three hop varieties (Agnus, Saaz hop - Osvald's clone 31, Vital). There were no statistically significant intervarietal differences in measured K (overall mean 1.68 × 10-6 m4/MPa/s), the ratio between K and theoretical conductivity (mean = 0.194), as well as vessel diameter and vessel length distributions. The only noticeable difference was in the distribution of vessels with the diameter ≥ 100 μm which differed in Vital compared to Agnus or Osvald's clone 31 (Kruskal-Wallis test, P < 0.001). Our results thus indicate highly conservative nature of xylem basic functional and anatomical characteristics in hop varieties studied.

Faltus M.,Czech Republic Crop Research Institute | Zamecnik J.,Czech Republic Crop Research Institute | Svoboda P.,Hop Research Institute | Patzak J.,Hop Research Institute | Nesvadba V.,Hop Research Institute
Acta Horticulturae | Year: 2011

In this study the applicability of a new cryopreservation method for conservation of hop germplasm was evaluated. Thirty-five cultivars of Humulus lupulus and one clone of Humulus japonicus were introduced into in vitro conditions, evaluated on viral infection, cryopreserved and recovered for tests of genotype tability. Altogether 72 independent experiments were performed for verification of the cryopreservation method. The average explant post-thaw recovery of all evaluated accessions was 38% whereas 72% accessions had post-thaw recovery higher than 30%. The results guaranteed successful recovery of all cryopreserved cultivars. Tests of genotype stability by SSR and STS analyses did not detect any changes due to cryopreservation.

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