Kvasny Prumysl, 2014 (vol. 60), issue 4
Wild yeasts and methods for their detection - Part II.Peer-reviewed article
Petra KUBIZNIAKOVÁ, Jana KOPECKÁ, Dagmar MATOULKOVÁ
Kvasny Prum. 2014; 60(4): 78-87 | DOI: 10.18832/kp2014008 
This study is a sequel to the preceding article "Microbiology of brewing - Wild yeasts and methods for their detection" (Matoulková et al., Kvasný Průmysl 59(9): 246-257, 2013). The growth was monitored of a set of 143 strains of culture (brewing and wine) and wild yeasts in selected selective media designed for the detection of wild yeasts: WLN agar, wort agar containing monoiodoacetic acid, lysine agar, agar with crystal violet and agar with copper sulphate. Yeast growth was further studied on MYGP agar plates containing the antibiotic actidione and on YPD agar medium at 37 °C. The usefulness of the media in the brewery laboratory was evaluated.This...
Summary Evaluation of bitter acids and polyphenols content in Czech hops harvest in 2013 - I: Contents of α- and β-Bitter Acids..Peer-reviewed article
Alexandr MIKYŠKA, Marie JURKOVÁ
Kvasny Prum. 2014; 60(4): 88-95 | DOI: 10.18832/kp2014009
The contents of α- and β- bitter acids from hops harvested in the Czech Republic in 2013 have been evaluated. The sampling was done in all three growing areas - Žatec (77.8% of the hop yard areas in the Czech Republic), Úštěk (10.6%) and Tršice (11.7%). The Saaz variety (ŽPČ) was cultivated on 87.8% of the harvest areas, the Sládek variety on 5.6%, Premiant variety on 4.7% and the Agnus variety on 1.0% of the harvest areas. The hops were analyzed in accordance with the Analytica-EBC, method 7.7 (HPLC) and all results are given in weight % in dry matter. The average value for α-bitter acids in the Saaz variety in the Czech Republic was...
Hop beta acids: Properties, significance and utilization.Peer-reviewed article
Karel KROFTA, Alexandr MIKYŠKA
Kvasny Prum. 2014; 60(4): 96-105 | DOI: 10.18832/kp2014010
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...