BACKGROUND: Although fatty acids have a beneficial effect on yeast growth during fermentation, their effect on foam and sensory stability of beer is negative. In general, long-chain fatty acids originate from raw materials, whereas short-chain acids are produced by yeast during fermentation. If the concentration of short-chain fatty acids, especially isovaleric and butyric acid, overreaches a sensory threshold, then an unpleasant aroma, such as cheesy or sweaty feet, can be formed in beer. RESULTS: The distribution of fatty acids, from the preparation of sweet wort to the final beer, was studied using chemometric evaluation. Differences were observed between the decoction and infusion system using four barley varieties. Attention was paid to the behavior of short-chain fatty acids, namely isovaleric acid. The concentration of isovaleric acid in commercial beers brewed in infusion and decoction systems was approximately 1.4 and 1.0 mg L-1 , respectively. The same trend was observed in experimental samples (1.3 and 0.5 mg L-1 , respectively). This phenomenon was confirmed experimentally; based on the results, this possibly explains why, during the fermentation, isovaleric acid is coupled with the redox state of yeast cell, which is given by the wort composition (i.e. by the mashing process). CONCLUSION: The formation of isovaleric acid is not only caused by microbiology infection or by oxidized hops, but also is influenced by the mashing process. © 2018 Society of Chemical Industry.
- MeSH
- chuť MeSH
- fermentace MeSH
- Humulus chemie metabolismus MeSH
- ječmen (rod) chemie metabolismus MeSH
- lidé MeSH
- manipulace s potravinami MeSH
- mastné kyseliny chemie metabolismus MeSH
- oxidace-redukce MeSH
- pivo analýza MeSH
- Saccharomyces cerevisiae metabolismus MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Three bottles of different beers were found in 2015 during a reconstruction of the brewery of the Raven Trading s.r.o. company in Záhlinice, Czech Republic. Thanks to good storage conditions, it was possible to analyze their original characteristics. All three bottles contained most probably lager type beer. One beer had sulfuric and fecal off-flavors; it was bright with the original extract of 10.3° Plato. The second beer, with an original extract of 7.6° Plato, was dark and very acidic, resembling Lambic. DNA analysis proved the presence of Dekkera bruxellensis, which corresponded to its chemical profile (total acidity, FAN, ethyl acetate, total esters). The third beer contained traces of carbon dioxide bubbles, was light brown and slightly bitter, with an original extract 10.4° Plato. Because it obviously underwent a natural aging process, sweetness, honey, and fruity off-flavors were detected and transformation products of iso-α-acids were found.
- MeSH
- časové faktory MeSH
- chuťové esence analýza MeSH
- Dekkera genetika izolace a purifikace metabolismus MeSH
- fermentace MeSH
- kyseliny analýza MeSH
- lidé MeSH
- manipulace s potravinami MeSH
- mastné kyseliny analýza MeSH
- pivo analýza mikrobiologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Česká republika MeSH
Hops are a well-known source of resins, essential oils and polyphenolic substances, such as proanthocyanidins or prenylflavonoids with significant representatives of xanthohumol, isoxanthohumol, and 8-prenylnaringenine, and represent an essential ingredient in beer production. Recently, however, many additional bioactive effects of hop compounds have been investigated. A systematic review of the structure-function relationship between the individual hop-derived compounds and their bio-activity has been lacking. In this review we summarize some recent findings in this area from reports from our as well as other studies. It shows multiple bio-medical effects of the individual hop derived compounds, which can act individually, or in a synergistic manner. The hops can serve as a source of bio-active compounds in phyto-medicine and as such, more attention and detailed studies are warranted to utilize the broad spectrum of effects of individual compounds in future treatments.
- MeSH
- antibakteriální látky izolace a purifikace MeSH
- fytoterapie MeSH
- Humulus chemie MeSH
- oleje rostlin chemie terapeutické užití MeSH
- polyfenoly chemie terapeutické užití MeSH
- rostlinné extrakty chemie terapeutické užití MeSH
- rostlinné pryskyřice chemie terapeutické užití MeSH
- Publikační typ
- práce podpořená grantem MeSH
A new ultra high-performance liquid chromatography method with UV detection was examined for detection and separation of polychlorinated biphenyls. This included optimization of separation conditions for two model mixtures containing seven and fifteen most relevant congeners, comparison of three types of reversed phase sub-2-micron particle sized columns and assessment of system suitability under the optimized conditions. Calibration curves determined in the range from 0.5 to 50.0 microg/mL exhibited correlation coefficients ranging from 0.997 to 0.999. Lower limits of detection ranged from 0.1 to 0.5 ppm. The most efficient Grace C18 column filled with 1.5 microm particles was then tested to separate the complex commercial mixture Delor 103, where the elution order was confirmed by GC-MS. 13 individual congeners were separated and some of the other co-eluting congeners could be resolved using another separation dimension performed with a mass spectrometry detector. The developed method could be directly applied to the separation of less complex mixtures in aqueous sample matrixes, which are used in general for enzyme degradation studies.
- MeSH
- kalibrace MeSH
- limita detekce MeSH
- plynová chromatografie s hmotnostně spektrometrickou detekcí MeSH
- polychlorované bifenyly izolace a purifikace MeSH
- vysokoúčinná kapalinová chromatografie přístrojové vybavení metody MeSH
- Publikační typ
- časopisecké články MeSH
- hodnotící studie MeSH
- práce podpořená grantem MeSH
A new separation and quantification method using ultra-performance liquid chromatography (UPLC) with UV detection was developed for detection of lincomycin traces in fermentation broth of different Streptomyces spp. A similar high-performance liquid chromatography (HPLC) protocol was simultaneously developed for comparison purposes. Both methods were validated and showed a linear range of detector response for quantification of lincomycin in concentration from 3.125 to 1000.0 microgml(-1) with correlation coefficient 0.999 and recoveries ranging from 81.5 to 89.85% with precision < or =5%. Compared with the HPLC, the UPLC method offered high sample throughput and about 10 times lower consumption of solvents. The developed assays were used for determination of lincomycin production in genetically manipulated production strain Streptomyces lincolnensis and for determination of lincomycin production after heterologous expression of lincomycin biosynthetic gene cluster in non-producing strain Streptomyces coelicolor.
- MeSH
- chromatografie kapalinová metody MeSH
- fermentace MeSH
- financování organizované MeSH
- geneticky modifikované organismy metabolismus MeSH
- linkomycin analýza MeSH
- senzitivita a specificita MeSH
- spektrofotometrie ultrafialová metody MeSH
- Streptomyces genetika metabolismus MeSH
- vysokoúčinná kapalinová chromatografie metody MeSH
An assay of L-tyrosine (Tyr) hydroxylating activity operating in lincomycin biosynthesis is described. The assay development consisted of HPLC procedure development, assessing the effect of reaction mixture components on non-enzymatic Dopa and Tyr oxidation, and sample stability evaluation. The HPLC procedure with isocratic elution and fluorescence detection was developed and validated. The method showed a wide linear range of Dopa determination of 0.125-25 micromol/L with lower limit of quantification (LLOQ) of 0.125 micromol/L, RSD of 7.2% and accuracy of 101.7%. The studied linear range of Tyr was 15.625 mmol/L to 500 mmol/L with LLOQ of 15.625 mmol/L, RSD of 1.1%, and accuracy of 98.1%. Recoveries for Dopa and Tyr were 100.66 +/- 0.89% and 94.76 +/- 0.94%, respectively. The inter- and intra-day accuracies and precisions were all within 10%. Samples of the reaction mixture were stable for at least 24 h at room temperature (RT) and 28 days at -20 degrees C. The method was tested for the enzyme activity monitoring in purified as well as crude preparations and enabled micro preparation of the enzyme product during confirmation of its identity. The influence of pH and ascorbic acid content in reaction mixture was studied with respect to non-enzymatic Tyr oxidation.
- MeSH
- aktivace enzymů MeSH
- biotest MeSH
- časové faktory MeSH
- dopaminové látky analýza chemie MeSH
- financování organizované MeSH
- koncentrace vodíkových iontů MeSH
- levodopa analýza chemie MeSH
- oxidace-redukce MeSH
- reprodukovatelnost výsledků MeSH
- senzitivita a specificita MeSH
- stabilita léku MeSH
- teplota MeSH
- tyrosin-3-monooxygenasa analýza metabolismus MeSH
- tyrosin analýza MeSH
- vysokoúčinná kapalinová chromatografie metody MeSH
