Effects of quinoa and amaranth on zinc,magnesium and calcium content in beer wort

Pseudocereals such as quinoa and amaranth can be used as partial replacements for malt in the production of new beers. Quinoa and amaranth are of interest due to their high levels of nutrients and micronutrients, including minerals which can significantly improve the performance of brewing yeast and the fermentation rate. In this study, we investigated whether the use of quinoa or amaranth as partial replacements for malt affected the concentration of ions such as zinc and magnesium in beer wort. The use of amaranth, and in particular quinoa, increased the content of both zinc and magnesium ions substantially, even when only 10% of the barley malt was replaced. With 10% quinoa, Zn²⁺ and Mg²⁺ content increased by 41% and 49%, respectively, while the ratio of Mg²⁺ to Ca²⁺ rose from 1.4:1 to 1.9:1. Use of unmalted quinoa and amaranth appears a good way of enriching wort with essential metal ions.     

Synthesis,Surface Activity,and Biological Activities of Phosphonium and Metronidazole Salts

A series of phosphonium amphiphilic compounds was synthesized. Cationic parts of molecules contain triphenylphosphonium moieties. Lipophilic parts of compounds are represented by straight alkyl chain or the alkyl chains which are ornamented by benzyl or metronidazole. The physicochemical properties of phosphonium amphiphilic compounds were investigated by the measurements of surface tension and conductivity. The critical micelle concentration (cmc), the surface tension value at the cmc (γ_cmc), the surface area at the surface saturation per head group (A_cmc) were determined. The lowest cmc value was determined for phosphonium salts with straight dodecyl alkyl chain. Its value was 1.5 × 10⁻³ mol dm⁻³. Surface tension at the cmc decreases with the addition of bulky moieties (benzyl, radical from metronidazol) at the end of alkyl chains. Biological activities of compounds were studied on human erythrocytes and strains of Acanthamoeba lugdunensis and Acanthamoeba quina. Dodecyltriphenylphosphonium bromide showed the highest activity against Acanthamoeba. To the best of our knowledge, it is the first compound of the group of phosphonium amphiphiles, which exhibited high activity against Acanthamoeba. The determined structure–activity relationship indicated nonspecific trophocidal and hemolytic activity that depends on physicochemical properties of the studied compounds.     

How the replacement of cholesterol by 25-hydroxycholesterol affects the interactions with sphingolipids: The Langmuir Monolayer Study complemented with theoretical calculations

In this paper, a representative of chain-oxidized sterols, 25-hydroxycholesterol (25-OH), has been studied in Langmuir monolayers mixed with the sphingolipids sphingomyelin (SM) and ganglioside (GM₁) to build lipid rafts. A classical Langmuir monolayer approach based on thermodynamic analysis of interactions was complemented with microscopic visualization of films (Brewster angle microscopy), surface-sensitive spectroscopy (polarization modulation–infrared reflection–absorption spectroscopy) and theoretical calculations (density functional theory modelling and molecular dynamics simulations). Strong interactions between 25-OH and both investigated sphingolipids enabled the formation of surface complexes. As known from previous studies, 25-OH in pure monolayers can be anchored to the water surface with a hydroxyl group at either C(3) or C(25). In this study, we investigated how the presence of additional strong interactions with sphingolipids modifies the surface arrangement of 25-OH. Results have shown that, in the 25-OH/GM₁ system, there are no preferences regarding the orientation of the 25-OH molecule in surface complexes and two types of complexes are formed. On the other hand, SM enforces one specific orientation of 25-OH: being anchored with the C(3)–OH group to the water. The strength of interactions between the studied sphingolipids and 25-OH versus cholesterol is similar, which indicates that cholesterol may well be replaced by oxysterol in the lipid raft system. In this way, the composition of lipid rafts can be modified, changing their rheological properties and, as a consequence, influencing their proper functioning.     

Emissions of ultrafine particles from five types of candles during steady burn conditions

Emissions from candles are of concern for indoor air quality. In this work, five different types of pillar candles were burned under steady burn conditions in a new laboratory scale system for repeatable and controlled comparison of candle emissions (temperature ~25°C, relative humidity ~13%, O₂ >18%, air exchange rate 1.9 h⁻¹). Burn rate, particle number concentrations, mass concentrations, and mode diameters varied between candle types. Based on the results, the burning period was divided in two phases: initial (0–1 h) and stable (1–6 h). Burn rates were in the range 4.4–7.3 and 4.7–7.1 g/h during initial and stable phase, respectively. Relative particle number emissions, mode diameters, and mass concentrations were higher during the initial phase compared to the stable phase for a majority of the candles. We hypothesize that this is due to elevated emissions of wick additives upon ignition of the candle together with a slightly higher burn rate in the initial phase. Experiments at higher relative humidity (~40%) gave similar results with a tendency toward larger particle sizes at the higher relative humidity. Chemical composition with respect to inorganic salts was similar in the emitted particles (dry conditions) compared to the candlewicks, but with variations between different candles.     

β‐Aminopeptidase‐Catalyzed Biotransformations of β2‐Dipeptides: Kinetic Resolution and Enzymatic Coupling

We have previously shown that the β‐aminopeptidases BapA from Sphingosinicella xenopeptidilytica and DmpA from Ochrobactrum anthropi can catalyze reactions with non‐natural β³‐peptides and β³‐amino acid amides. Here we report that these exceptional enzymes are also able to utilize synthetic dipeptides with N‐terminal β²‐amino acid residues as substrates under aqueous conditions. The suitability of a β²‐peptide as a substrate for BapA or DmpA was strongly dependent on the size of the C_α substituent of the N‐terminal β²‐amino acid. BapA was shown to convert a diastereomeric mixture of the β²‐peptide H‐β²hPhe‐β²hAla‐OH, but did not act on diastereomerically pure β²,β³‐dipeptides containing an N‐terminal β²‐homoalanine. In contrast, DmpA was only active with the latter dipeptides as substrates. BapA‐catalyzed transformation of the diastereomeric mixture of H‐β²hPhe‐β²hAla‐OH proceeded along two highly S‐enantioselective reaction routes, one leading to substrate hydrolysis and the other to the synthesis of coupling products. The synthetic route predominated even at neutral pH. A rise in pH of three log units shifted the synthesis‐to‐hydrolysis ratio (v_S/v_H) further towards peptide formation. Because the equilibrium of the reaction lies on the side of hydrolysis, prolonged incubation resulted in the cleavage of all peptides that carried an N‐terminal β‐amino acid of S configuration. After completion of the enzymatic reaction, only the S enantiomer of β²‐homophenylalanine was detected (ee>99 % for H‐(S)‐β²‐hPhe‐OH, E>500); this confirmed the high enantioselectivity of the reaction. Our findings suggest interesting new applications of the enzymes BapA and DmpA for the production of enantiopure β²‐amino acids and the enantioselective coupling of N‐terminal β²‐amino acids to peptides.     

Effect of l-ascorbic acid, sugar, pectin and freeze-thaw treatment on polyphenol content of frozen strawberries

The stability of phenolic compounds of three strawberry cultivars was evaluated for changes during prefreezing treatments, storage and various freezing and thawing conditions. Polyphenol content was determined by HPLC-DAD-FL. The sum of assayed polyphenolic (proanthocyanidin and monomeric flavan-3-ols, anthocyanins, ellagic acid, p-coumaric acid) represented 2858.4 mg/kg in Kent, 2893.1 mg/kg in Elkat, and 2438.0 mg/kg in Senga Sengana. After freezing, 4.5-33.6% of polyphenols were lost; protective effects of prefreezing treatments were seen on anthocyanidins and proanthocyanidins: ascorbic acid was the most effective pretreatment, allowing retention of 3.9-27.5% of anthocyanins, and almost total recovery (3.9-23.9%) when associated with liquid nitrogen freezing. Pectin and sugar only allowed retention of 3.0-25.1% and 5.5-25.4% of the antocyanins, respectively. Thawing of the strawberries in a microwave oven (instead of 20 h at 20 °C) had a further positive effect on retention of anthocyanins, proanthocyanins, (+)-catechin and ellagic acid.     

A comparative study for determination of biogenic amines in meat samples by capillary isotachophoresis with two electrolyte systems

The selected biogenic amines, BAs (putrescine, cadaverine, histamine, tyramine, spermidine and spermine), in pork, beef, and poultry meat samples were determined by two simple procedures without derivatization using isotachophoretic technique. Two electrolyte systems were proposed for their separation and determination with satisfactory separation parameters. The linearity of the proposed procedures was between 2–10 mg L^?1 and 5–50 or 10–60 mg L^?1, whereas average recoveries for the standard solutions of amines and their mixture varied between 99–100 % and 95–105 %, respectively. Average recoveries for standard addition method (96–99 %) indicated satisfactory accuracy of proposed electrolyte systems. The obtained coefficient of variation values for standard solutions and meat samples ranged from 0.62 to 4.54 % and from 0.56 to 6.03 %, respectively, which confirmed good repeatability. Except for spermidine and spermine, BAs levels in fresh meat samples were generally low. The effect of storage time on the content of biogenic amines in meat was also studied indicating the increase of BAs levels (excluding Spermine and Spermidine).