Aims
Isolation, characterization and identification of possible microbial contaminant(s) in the inflated foil bag containing hop pellets packed and stored in a modified atmosphere.
Methods and ...results
Package gas of the inflated foil bag containing hop pellets was analysed by gas chromatography. Compared with the reference modified atmosphere, containing about 16 vol.% of CO2, the inflated bag atmosphere contained 53 vol.% CO2, suggesting possible microbial contamination. Therefore, several standard and mineral media, with added hop pellets or hop infusion, were used for cultivation at different temperatures under an anaerobic atmosphere. Cultivation in mineral medium with hop pellets yielded a bacterial isolate that was identified by MALDI‐TOF mass spectrometry and verified by partial 16S rRNA gene analysis as Pantoea agglomerans, a known plant epiphyte.
Conclusions
A novel strain of P. agglomerans (designed as DBM 3696) was found to be suspicious of causing inflation of the foil bag containing dried hop pellets packed in modified atmosphere.
Significance and Impact of the Study
This study suggests that P. agglomerans, probably hop epiphyte, could cause sporadic inflation of bags with hop pellets packed in modified atmosphere causing logistical problems during bags transport.
The fate of five Fusarium toxins - deoxynivalenol (DON), sum of 15- and 3-acetyl-deoxynivalenol (ADONs), HT-2 toxin (HT-2) representing the main trichothecenes and zearalenone (ZON) during the ...malting and brewing processes - was investigated. In addition to these 'free' mycotoxins, the occurrence of deoxynivalenol-3-glucoside (DON-3-Glc) was monitored for the first time in a beer production chain (currently, only DON and ZON are regulated). Two batches of barley, naturally infected and artificially inoculated with Fusarium spp. during the time of flowering, were used as a raw material for processing experiments. A highly sensitive procedure employing high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was validated for the analysis of 'free' Fusarium mycotoxins and DON-conjugate in all types of matrices. The method was also able to detect nivalenol (NIV), fusarenon-X (FUS-X) and T-2 toxin (T-2); nevertheless, none of these toxins was found in any of the samples. While steeping of barley grains (the first step in the malting process) apparently reduced Fusarium mycotoxin levels to below their quantification limits (5-10 micrograms kg-1), their successive accumulation occurred during germination. In malt, the content of monitored mycotoxins was higher compared with the original barley. The most significant increase was found for DON-3-Glc. During the brewing process, significant further increases in levels occurred. Concentrations of this 'masked' DON in final beers exceeded 'free' DON, while in malt grists this trichothecene was the most abundant, with the DON/DON-3-Glc ratio being approximately 5:1 in both sample series. When calculating mass balance, no significant changes were observed during brewing for ADONs. The content of DON and ZON slightly decreased by a maximum of 30%. Only traces of HT-2 were detected in some processing intermediates (wort after trub removal and green beer).
Protons are the dominant particles both in galactic cosmic rays and in solar particle events and, furthermore, proton irradiation becomes increasingly used in tumour treatment. It is believed that ...complex DNA damage is the determining factor for the consequent cellular response to radiation. DNA plasmid pBR322 was irradiated at U120-M cyclotron with 30 MeV protons and treated with two Escherichia coli base excision repair enzymes. The yields of SSBs and DSBs were analysed using agarose gel electrophoresis. DNA has been irradiated in the presence of hydroxyl radical scavenger (coumarin-3-carboxylic acid) in order to distinguish between direct and indirect damage of the biological target. Pure scavenger solution was used as a probe for measurement of induced OH· radical yields. Experimental OH· radical yield kinetics was compared with predictions computed by two theoretical models-RADAMOL and Geant4-DNA. Both approaches use Geant4-DNA for description of physical stages of radiation action, and then each of them applies a distinct model for description of the pre-chemical and chemical stage.
Traditional beer fermentation and maturation processes use open fermentation and lager tanks. Although these vessels had previously been considered indispensable, during the past decades they were in ...many breweries replaced by large production units (cylindroconical tanks). These have proved to be successful, both providing operating advantages and ensuring the quality of the final beer. Another promising contemporary technology, namely, continuous beer fermentation using immobilized brewing yeast, by contrast, has found only a limited number of industrial applications. Continuous fermentation systems based on immobilized cell technology, albeit initially successful, were condemned to failure for several reasons. These include engineering problems (excess biomass and problems with CO2 removal, optimization of operating conditions, clogging and channeling of the reactor), unbalanced beer flavor (altered cell physiology, cell aging), and unrealized cost advantages (carrier price, complex and unstable operation). However, recent development in reactor design and understanding of immobilized cell physiology, together with application of novel carrier materials, could provide a new stimulus to both research and application of this promising technology.
Biosorption of Cd
2+, Cu
2+ and Ag
+ ions by C-, N-, P-, S-, Mg- and K-limited cells of
Saccharomyces cerevisiae was examined. Raman spectroscopy and analysis of elemental composition were used to ...identify differences between individual yeast cultures. K-, Mg- and C-limited cells accumulated the greatest amounts of Cd
2+ ions. The greatest amount of Cu
2+ ions was bound by biomass grown in K-limited medium. P-limited cells bound the greatest amount of Ag
+ ions, but in contrast they had the lowest sorption capacity for Cd
2+ ions. The smallest amounts of Cu
2+ and Ag
+ ions was bound by biomass grown in S-limited medium.
Determination of gluten in glucose syrups Dostálek, P.; Gabrovská, D.; Rysová, J. ...
Journal of food composition and analysis,
11/2009, Letnik:
22, Številka:
7
Journal Article
Recenzirano
The gluten content in various glucose syrups was determined by two sandwich ELISA methods and one competitive ELISA. Different extraction solutions were used for ELISA methods. MALDI-TOF mass ...spectrometry and SDS-PAGE were also carried out as a complementary technique to ELISA methods. The analysis proved that glucose syrups analyzed in this work and used in many food products and gluten-free food products are safe for patients suffering from celiac disease. Four food products containing glucose syrup were analyzed with satisfactory results as well. One sample of chocolate bar has gluten content lower than the current limit for gluten-free foods. Gluten content above this limit was found in this chocolate bar after cocktail-gelatine extraction. This product is not labelled as gluten-free food. This fact shows that the analyses of gluten-free products are not simple and need more work and attention.
Influence of growing area, plant age, and virus infection on the contents of hop secondary metabolites Jelinek, L., Vysoka Skola Chemicko-technologicka, Prague (Czech Republic). Ustav Biotechnologie; Doleckova, M., Vysoka Skola Chemicko-technologicka, Prague (Czech Republic). Ustav Biotechnologie; Karabin, M., Vysoka Skola Chemicko-technologicka, Prague (Czech Republic). Ustav Biotechnologie ...
Czech Journal of Food Sciences,
01/2012, Letnik:
30, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Hops and hop products (pellets and extracts) belong to the major raw materials employed in brewing industry. Many effects such as the growing area, hop plant age, and virus infection influence the ...contents of the brewing-important hop secondary metabolites (alpha- and beta-bitter acids, essential oils, and polyphenols). The clones of the Czech cultivars Saaz and German cv. Taurus were used in this work and compared with the aim to investigate the influence of the effects mentioned on the contents of hop secondary metabolites.
Xanthohumol, a prenylated chalcone from hops and beer, is a phenolic compound that has received considerable attention in recent years. This compound has a range of interesting biological properties ...that may have therapeutic utility: anti-inflammatory, antioxidant, antilipoperoxidative activities as well as antiangiogenic, antiproliferative and apoptotic effects, mainly assessed in vitro studies that reasonably suggest a potential chemopreventive activity. Phenomenon how xanthohumol affects brewing yeast's metabolism, yeast viability and vitality were studied during the production of a xanthohumol enriched beer (10 mg/L xanthohumol). The results showed that yeast viability was slightly decreased by xanthohumol, but on the other hand yeast vitality in the xanthohumol enriched brewing trials was slightly better. The content of higher alcohols and esters was similar to the control in all the xanthohumol enriched brewing trials. In laboratory scale experiment about effect of xanthohumol on brewing yeast growing was done. No effect of xanthohumol on yeast growth was detected. Due to the fact that yeast viability was slightly decreased by xanthohumol, experiment with zymolyase was done. Yeast cells cultivated with xanthohumol are significantly more sensitive to zymolyase treatment.
The determination of polyphenols by spectrophotometric detection is complicated due to their low concentrations in beer. The beer samples have to be pre-concentrated before using the ...spectrophotometric detection for their quantification. An analytical method based on solid-phase extraction (SPE) and followed by high performance liquid chromatographic separation with diode-array detection was used for the determination of free gallic, protocatechuic, caffeic, p-coumaric, ferulic and salicylic acids, of (+)-catechin, (-)-epicatechin, and quercetin. Six different SPE cartridges were tested and three different types of elution with the most appropriate solvents (acetonitrile, acetone and methanol) were used. The performance of the HPLC method was assessed by the evaluation of parameters such as absolute recovery, relative standard deviation (lower than 10%), the limit of quantification, and the limit of detection. The polyphenol content in various types of Czech beer is presented.
In the continuous systems, such as continuous beer fermentation, immobilized cells are kept inside the bioreactor for long periods of time. Thus an important factor in the design and performance of ...the immobilized yeast reactor is immobilized cell viability and physiology. Both the decreasing specific glucose consumption rate ( qim) and intracellular redox potential of the cells immobilized to spent grains during continuous cultivation in bubble‐column reactor implied alterations in cell physiology. It was hypothesized that the changes of the physiological state of the immobilized brewing yeast were due to the aging process to which the immobilized yeast are exposed in the continuous reactor. The amount of an actively growing fraction (Xactim) of the total immobilized biomass ( Xim) was subsequently estimated at approximately Xactim = 0.12 gIB gC−1 (IB = dry immobilized biomass, C = dry carrier). A mathematical model of the immobilized yeast biofilm growth on the surface of spent grain particles based on cell deposition (cell‐to‐carrier adhesion and cell‐to‐cell attachment), immobilized cell growth, and immobilized biomass detachment (cell outgrowth, biofilm abrasion) was formulated. The concept of the active fraction of immobilized biomass (Xactim) and the maximum attainable biomass load (Xmaxim) was included into the model. Since the average biofilm thickness was estimated at ca. 10 μm, the limitation of the diffusion of substrates inside the yeast biofilm could be neglected. The model successfully predicted the dynamics of the immobilized cell growth, maximum biomass load, free cell growth, and glucose consumption under constant hydrodynamic conditions in a bubble‐column reactor. Good agreement between model simulations and experimental data was achieved.
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