Historically, hop cones (
) have been used since ancient times as a remedy for many ailments and, as a source of polyphenols and bitter acids, is very effective in the treatment of metabolic syndrome ...(MS). Hop flavonoids, particularly xanthohumol (XN), are substances with hypoglycemic, antihyperlipidemic, and antiobesity activities. Iso-α-acids (IAA) and matured hop bitter acids (MHBA) improve health by influencing lipid metabolism, glucose tolerance, and body weight. The modulatory effect of IAA and MHBA on lipid metabolism may also be responsible for a loss in body weight. These results suggest promising applications for IAA, MHBA, and XN in humans, particularly in the prevention of diet-induced obesity and diabetes.
The growth of micromycetes and the associated production of mycotoxins during malting represents a potential safety issue and an economic challenge regarding the quality of beer as a product ...manufactured from malt. The treatment of malted cereals with a pulsed electric field (PEF) may be one method to overcome this issue. In this work were tested PEF conditions that would lead to a reduction in fungal growth without suppressing germination and thus causing deterioration in the technological parameters of the malt. Pre-soaking the grain for more than 3.5 h prior to PEF treatment was found to significantly reduce the germination energy and, compared to the untreated sample, enzymatic activity of the resulting malt. Therefore, a modification consisting of a short pre-soaking (10 min) and PEF treatment (field intensity 3.8 kV/cm, 100 pulses with peak width 20 μs) in a high conductivity environment (0.05 mol/L phosphate buffer) was implemented. This treatment led to a reduction (up to 80%) in growth of some Fusarium species (F. sporotrichoides and F. poae) and the production of corresponding mycotoxins, mainly trichothecenes A and ennianthins. Moreover, the treated malt did not differ significantly from the control malt in terms of enzymatic activity.
•PEF treatment of barley immediately prior to malting reduced the levels of Fusarium ssp. in malt.•Reduced contamination of the malt led to a decrease in relevant mycotoxins.•Treatment under optimised conditions did not affect germination.•Malt produced from treated barley showed similar technological characteristics as the control.
Compared to most other alcoholic beverages, the shelf life of beer is much more limited due to its instability in the bottle. That instability is most likely to appear as turbidity (haze), even ...sedimentation, during storage. The haze in beer is mostly caused by colloidal particles formed by interactions between proteins and polyphenols within the beer. Therefore, beers are usually stabilized by removing at least one of these components. We developed and constructed a
Saccharomyces cerevisiae
strain with a proline-rich QPF peptide attached to the cell wall, using the C-terminal anchoring domain of α-agglutinin. The QPF peptide served to bind polyphenols during fermentation and, thus, to decrease their concentration. Strains displaying QPF were able to bind about twice as much catechin and epicatechin as a control strain displaying only the anchoring domain. All these experiments were done with model solutions. Depending on the concentration of yeast, uptake of polyphenols was 1.7–2.5 times higher. Similarly, the uptake of proanthocyanidins was increased by about 20 %. Since the modification of yeasts with QPF did not affect their fermentation performance under laboratory conditions, the display of QPF appears to be an approach to increase the stability of beer.
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.
Although female cones of the hop plant (Humulus lupulus) are known primarily as raw material supplying characteristic bitterness and aroma to beer, their equally significant health‐promoting effects ...have been known to mankind for several thousand years and hop is a plant traditionally utilized in folk medicine. This paper summarizes the scientific knowledge on the effects of all 3 major groups of secondary metabolites of hops; polyphenols, essential oils, and resins. Because of their chemical diversity, it is no coincidence that these compounds exhibit a wide range of pharmacologically important properties. In addition to antioxidant, anti‐inflammatory, and anticancer‐related properties, particular attention is being paid to prenylflavonoids that occur almost exclusively in hops and are considered to be some of the most active phytoestrogens known. Hop oils and resins are well known for their sedative and other neuropharmacological properties, but in addition, these compounds exhibit antibacterial and antifungal effects. Recently, alpha bitter acids have been shown to block the development of a number of complex lifestyle diseases that are referred to by the collective name “metabolic syndrome.” Information presented in this review confirms the significant potential for the use of hops in the pharmaceutical industry and provides an understanding of beer as a natural drink that, although moderately consumed, may become a source of many health‐promoting compounds.
Upper bounds on absorption and scattering Gustafsson, Mats; Schab, Kurt; Jelinek, Lukas ...
New journal of physics,
07/2020, Letnik:
22, Številka:
7
Journal Article
Recenzirano
Odprti dostop
A general framework for determining fundamental bounds in nanophotonics is introduced in this paper. The theory is based on convex optimization of dual problems constructed from operators generated ...by electromagnetic integral equations. The optimized variable is a contrast current defined within a prescribed region of a given material constitutive relations. Two power conservation constraints analogous to the optical theorem are utilized to tighten the bounds and to prescribe either losses or material properties. Thanks to the utilization of matrix rank-1 updates, modal decompositions, and model order reduction techniques, the optimization procedure is computationally efficient even for complicated scenarios. No dual gaps are observed. The method is well-suited to accommodate material anisotropy and inhomogeneity. To demonstrate the validity of the method, bounds on scattering, absorption, and extinction cross sections are derived first and evaluated for several canonical regions. The tightness of the bounds is verified by comparison to optimized spherical nanoparticles and shells. The next metric investigated is bi-directional scattering studied closely on a particular example of an electrically thin slab. Finally, the bounds are established for Purcell's factor and local field enhancement where a dimer is used as a practical example.
In recent years, the interest in the health-promoting effects of hop prenylflavonoids, especially its estrogenic effects, has grown. Unfortunately, one of the most potent phytoestrogens identified so ...far, 8-prenylnaringenin, is only a minor component of hops, so its isolation from hop materials for the production of estrogenically active food supplements has proved to be problematic. The aim of this study was to optimize the conditions (e.g., temperature, the length of the process and the amount of the catalyst) to produce 8-prenylnaringenin-rich material by the magnesium oxide-catalyzed thermal isomerization of desmethylxanthohumol. Under these optimized conditions, the yield of 8-prenylnaringenin was 29 mg per 100 gDW of product, corresponding to a >70% increase in its content relative to the starting material. This process may be applied in the production of functional foods or food supplements rich in 8-prenylnaringenin, which may then be utilized in therapeutic agents to help alleviate the symptoms of menopausal disorders.
The characteristic aroma of smoked malts and, subsequently, of the beers made from them, is mainly derived from phenols, guaiacols, syringols and some furan derivatives. These compounds are the ...products of pyrolysis, which are transferred to the malt during kilning by the smoke generated through the burning of wood or peat. In the work presented here, the contents of nine characteristic markers in two malts kilned by wood- and peat smoke as well as bottom- and top-fermented beers brewed exclusively from these malts, including intermediate products, were determined using HS-SPME coupled with GC–MS. Significant differences in the content and ratios of specified compounds were found for each type of malt. The peat-smoked malt contained up to 4 times higher levels of most analytes, with significantly higher phenol and cresols (4.2–16.5 mg.kg
−1
) compared to guaiacols (about 2 mg kg
−1
). In contrast, in wood-smoked malt, both groups of compounds were present at comparable levels between 1 and 2 mg kg
−1
. During mashing and wort-boiling, levels of volatile phenols decreased by up to 80% of their original amount. Significantly lower losses occurred during fermentation, and no significant differences were found for beers fermented using different yeasts. Nevertheless, most of the differences in the contents of the analysed compounds found in the malts were carried over to the beers. Differences in the composition of beers made from malts kilned using different materials were also confirmed statistically using cluster analysis by comparison with commercially available smoked beers.
This paper describes a powerful, yet simple, procedure how to acquire a current approaching the lower bound of quality factor Q. This optimal current can be determined for an arbitrarily shaped ...electrically small radiator made of a perfect conductor. Quality factor Q is evaluated by Vandenbosch's relations yielding stored electromagnetic energy as a function of the source current density. All calculations are based on a matrix representation of the integro-differential operators. This approach simplifies the entire development and results in a straightforward numerical evaluation. The optimal current is represented in a basis of modal currents suitable for solving the optimization problem so that the minimum is approached by either one mode tuned to the resonance, or, by two properly combined modes. An overview of which modes should be selected and how they should be combined is provided and results concerning rectangular plate, spherical shell, capped dipole antenna, and fractal shapes of varying geometrical complexity are presented. The reduction of quality factor Q and the G/ Q ratio are studied and, thanks to the modal decomposition, the physical interpretation of the results is discussed in conjunction with the limitations of the proposed procedure.
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