Determination of Magnetic and Nuclear Quadrupole Interactions in La@C82 from EPR Linewidth Data

From the analysis of the temperature dependence of the EPR line width, an estimate of the anisotropic parts of the dipolar and quadrupolar hyperfine couplings of lanthanum was derived. Furthermore, the rotational correlation time of the nearly spherical molecule was found to deviate considerably from that of the solvent molecules.     

Analytical Characterization of the Hydrolysis of Barley Malt Macromolecules During Enzymatic Degradation Over Time Using AF4/MALS/RI

The changes on the molecular weight distribution (MWD) and particle size distribution (PSD) during hydrolysis of barley malt in isothermal mashing procedures were determined using asymmetrical flow field flow fractionation coupled to multiangle laser light scattering and refractive index (AF4/MALS/RI). Mash/trials were focused on amylolytic starch degradation. Therefore, temperatures (65, 70, and 75 °C) were selected according to α‐ and β‐amylases range of activity. Samples were produced by triplicate, tracking amylolytic processes over time periods from 10 to 90 min in each mash/trial. AF4/MALS/RI analysis demonstrated significant differences on the values of the MWD and PSD according to the temperature/time profile used. At mashing times over 30 min at a temperature of 65 °C, when α‐ and β‐amylase are both active, the decrease over time of the MWD and PSD was significantly higher (P < 0.005) than at 70 °C when mainly α‐amylase is active. At 75 °C, also the activity of α‐amylase decreased and the MWD and PSD were significantly lower (P < 0.005) than at 70 or 65 °C at any time of the procedure. The MWD and PSD of beer components influence beer palate fullness, thus AF4/ MALS/RI would be a powerful tool for breweries to adapt their technological processes to obtain beers with particular sensorial attributes.     

Determination of the influence of starch sources and mashing procedures on the range of the molecular weight distribution of beer using field‐flow fractionation

To produce experimental beers, different mash mixtures (barley malt, barley malt + 30% pre‐cooked maize, barley malt + 30% nonmalted spelt) and distinct mashing procedures (infusion and decoction) with variations of the rest time and initial temperatures were evaluated. The range of molecular weight distribution (MWD) of the resulting beers was determined using asymmetrical flow field flow fractionation coupled to multiangle laser light scattering and refractive index. There were no differences on the range of MWD among the beers, according to infusion or decoction, using similar raw materials and initial temperatures (45 and 55°C). However the range of MWD was higher (p < 0.005) when using infusion at an initial temperature of 63°C, regardless of the raw material. The use of maize did not alter structural properties of the beer, while mash containing nonmalting spelt caused an elevation on the MWD (p < 0.001) and a lower (p < 0.05) apparent degree of fermentation. Therefore the range of the MWD of the beers was influenced by the quality of the raw material and the initial mashing temperature, whereas apparent degree of fermentation values were affected only by the type of starch source. Thus the determination of the MWD is an important tool for monitoring the production of beer. Copyright © 2013 The Institute of Brewing & Distilling     

Determination of Magnetic and Nuclear Quadrupole Interactions in La@C82 from EPR Linewidth Data

Abstract

From the analysis of the temperature dependence of the EPR line width, an estimate of the anisotropic parts of the dipolar and quadrupolar hyperfine couplings of lanthanum was derived. Furthermore, the rotational correlation time of the nearly spherical molecule was found to deviate considerably from that of the solvent molecules.     

Effect of structurally different microbial homoexopolysaccharides on the quality of gluten-free bread

The effect of structurally different bacterial homoexopolysaccharides on gluten-free bread quality and their properties to act as hydrocolloids was investigated. Furthermore, exopolysaccharides (EPS) were analyzed structurally by asymmetrical flow field flow fractionation and methylation analysis. Breads were made of buckwheat and rice flour with EPS of Lactobacillus (L.) curvatus TMW 1.624, L. reuteri TMW 1.106, L. animalis TMW 1.971, and L. sanfranciscensis TMW 1.392 or hydroxypropylmethylcellulose (HPMC) at 1?% w/w flour base. Water-holding capacity, specific volume, crumb analysis, baking loss, moisture content, and crumb hardness were determined. Only HPMC and the glucan of L. curvatus TMW 1.624 retained water, and all supplements increased the specific volume. Furthermore, crumb hardness was decreased by additives to different extents. The moisture content, baking loss, and crumb firmness were improved most by dextran of L. curvatus TMW 1.624. Structure analysis of EPS revealed that L. animalis TMW 1.971 produces a fructan and a glucan and that the dextran of L. curvatus TMW 1.624 had highest molecular weight of analyzed EPS, ranging from 118 to 242 MDa. A methylation analysis demonstrated differences in branching. Dextran of L. reuteri TMW 1.106 is branched in position 4 (18?C19?%), whereas dextran of L. curvatus TMW 1.624 is branched in position 3 (8?C9?%). Overall, this study gives insight into structure function relations of different EPS. A structure function relation is suggested in which high weight average molar mass (Mw) and branching at position 3 of the glucose monomer foster a compact conformation of the molecule, which enables an increased water-binding capacity and promotes superior (structural) effects in gluten-free breads. The dextran of L. curvatus TMW 1.624 was the most promising candidate for applications in gluten-free bread quality improvements as it retains its size distribution and root mean square even with increasing Mw and forms an increasingly compact molecule.     

An overview of separation methods in starch analysis: The importance of size exclusion chromatography and field flow fractionation

Starch is the most important source of human food energy and also an important polymer for biofuels, processed food, and pharmaceutical industries. Precise determination of structural and functional properties of starch has been an outstanding factor for the improvement of dissolution and degradation processes, which are important procedures for commercial applications. Distinct separation techniques coupled with multiple detection methods such as Size Exclusion Chromatography (SEC), Field Flow fractionation (FFF), Analytical Ultracentrifugation, and Hydrodynamic Chromatography have provided powerful information about starch conformation. In the present review, we describe the usefulness and limitations of different separation methods particularly SEC and FFF, which are currently widely used.     

Influence of the range of molecular weight distribution of beer components on the intensity of palate fullness

The effect of the molecular weight distribution (MWD) of the beer components on the intensity of palate fullness was studied. The range of MWD for different types of maltodextrin and for nine commercial pilsner beers was determined using AF4/MALLS/RI. Sensory analysis (DIN 10952, DIN ISO 4120 and DIN 10963/ISO 8587) was carried out by a trained Deutsche Landwirtschafts-Gesellschaft, German Agriculture Society (DLG) tasting panel. The intensity of the palate fullness of a spiking trial (beer + maltodextrin) and the threshold concentration of the maltodextrins in beer was determined. The association between the ranges of MWD and the intensity of the palate fullness of the commercial pilsner beers was studied. AF4/MALLS/RI and sensory analysis were used to study the effect of variations of the brewing process on the range of MWD and the palate fullness of beer. The intensity of the palate fullness differed significantly (p < 0.0001) within commercial pilsner beers. Strong associations were found between the range of MWD of the commercial beers and intensity of the palate fullness (p < 0.05). The range of MWD of the commercial pilsner beers (3–13 kDa) corresponded to those found for maltodextrins with intermediated range of MWD (3.4–22.3 kDa). The threshold concentration was higher (p < 0.0001) for those maltodextrins with lower range of MWD (2.7–8.9 kDa). Beers produced with malted barley with Kolbach Index of 36 % exhibited a higher range of MWD (2.9–13 kDa) compared to those with Kolbach Index of 41 % (1.7–11.6 kDa). Slight differences in the palate fullness were perceived according to variations on the initial temperature of the mashing process among those beers produced using Kolbach Index of 36 %, whereas a great difference (p < 0.0001) was perceived using Kolbach Index of 41 %. The intensity of the palate fullness of the pilsner beer was influenced by the range of MWD of the beer components which would vary according to differences in the mashing process and of the quality of the malted barley.     

Identification of Lactobacillus curvatus TMW 1.624 dextransucrase and comparative characterization with Lactobacillus reuteri TMW 1.106 and Lactobacillus animalis TMW 1.971 dextransucrases

Recently, it was affirmed that the exopolysaccharides (EPSs) of Lactobacillus curvatus TMW 1.624, Lactobacillus reuteri TMW 1.106 and Lactobacillus animalis TMW 1.971 improve the quality of gluten-free breads and that they can be produced in situ to levels enabling baking applications. In this study we provide insight into the molecular and biochemical background of EPS production of these three strains. EPS formation strongly correlated with growth and took place during the exponential phase. Gtf genes were heterologously expressed, purified and their enzymatic properties as well as the structures of the EPSs formed were compared. Structural comparison of EPS formed by heterologously expressed glucosyltransferases (Gtfs) and of those formed by the wildtype lactobacilli confirmed that the respective genes/enzymes were identified and examined. The glucan formed by L. animalis Gtf was identified as a linear low molecular weight dextran. Optimal enzymatic conditions were pH 4.4 and 45 °C for the L. reuteri Gtf and pH 4.4 and 31 °C for L. curvatus Gtf. The Gtf from L. animalis had an optimal pH of 5.8 and displayed more than 50% of activity over a broad temperature profile (22–59 °C). The three Gtfs were stimulated by various mono- and divalent metal ions, dextran, as well as levan to different extents.