Molecular brewing: molecular structural effects involved in barley malting and mashing

Ten barley samples containing varied protein contents were subject to malting followed by mashing to investigate molecular effects of both barley starch and starch- protein interactions on malting and mashing performances, and the underlying mechanism. Starch granular changes were examined using differential scanning calorimetry and scanning electron microscopy. The molecular fine structures of amylose and amylopectin from unmalted and malted grain were obtained using size-exclusion chromatography. The results showed that both amylose and amylopectin polymers were hydrolyzed at the same time during malting. Protein and amylose content in both unmalted and malted barley significant negatively correlated with fermentable sugar content after mashing. While protein content is currently the main criterion for choosing malting varieties, this study shows that information about starch molecular structure is also useful for determining the release of fermentable sugars, an important functional property. This provides brewers with some new methods to choose malting barley

Critical current density: Measurements vs. reality

Different experimental techniques are employed to evaluate the critical current density (Jc), namely transport current measurements and two different magnetisation measurements forming quasi-equilibrium and dynamic critical states. Our technique-dependent results for superconducting YBa 2Cu3O7 (YBCO) film and MgB2 bulk samples show an extremely high sensitivity of Jc and associated interpretations, such as irreversibility fields and Kramer plots, which lose meaning without a universal approach. We propose such approach for YBCO films based on their unique pinning features. This approach allows us to accurately recalculate the magnetic-field-dependent Jc obtained by any technique into the Jc behaviour, which would have been measured by any other method without performing the corresponding experiments. We also discovered low-frequency-dependent phenomena, governing flux dynamics, but contradicting the considered ones in the literature. The understanding of these phenomena, relevant to applications with moving superconductors, can clarify their dramatic impact on the electric-field criterion through flux diffusivity and corresponding measurements. © Copyright EPLA, 2013

A three-way comparative genomic analysis of Mannheimia haemolytica isolates

<p>Abstract</p> <p>Background</p> <p><it>Mannhemia haemolytica </it>is a Gram-negative bacterium and the principal etiological agent associated with bovine respiratory disease complex. They transform from a benign commensal to a deadly pathogen, during stress such as viral infection and transportation to feedlots and cause acute pleuropneumonia commonly known as shipping fever. The U.S beef industry alone loses more than one billion dollars annually due to shipping fever. Despite its enormous economic importance there are no specific and accurate genetic markers, which will aid in understanding the pathogenesis and epidemiology of <it>M. haemolytica </it>at molecular level and assist in devising an effective control strategy.</p> <p>Description</p> <p>During our comparative genomic sequence analysis of three <it>Mannheimia haemolytica </it>isolates, we identified a number of genes that are unique to each strain. These genes are "high value targets" for future studies that attempt to correlate the variable gene pool with phenotype. We also identified a number of high confidence single nucleotide polymorphisms (hcSNPs) spread throughout the genome and focused on non-synonymous SNPs in known virulence genes. These SNPs will be used to design new hcSNP arrays to study variation across strains, and will potentially aid in understanding gene regulation and the mode of action of various virulence factors.</p> <p>Conclusions</p> <p>During our analysis we identified previously unknown possible type III secretion effector proteins, clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated sequences (Cas). The presence of CRISPR regions is indicative of likely co-evolution with an associated phage. If proven functional, the presence of a type III secretion system in <it>M. haemolytica </it>will help us re-evaluate our approach to study host-pathogen interactions. We also identified various adhesins containing immuno-dominant domains, which may interfere with host-innate immunity and which could potentially serve as effective vaccine candidates.</p

Improved methodology for analyzing relations between starch digestion kinetics and molecular structure

A new combined methodology for obtaining relations between starch molecular structure and digestion kinetics of starch-based foods is illustrated using published data on cooked rice. Digestibility data are treated with the logarithm of slopes method, giving region(s) where first-order loss kinetics are applicable; accurate values for the rate parameters are obtained by non-linear least-squares. A new method is developed to find independent structural variables for whole and enzymatically-debranched starches. Chain-length distributions of amylose and amylopectin are fitted with models using biologically-meaningful parameters, including accounting for SEC band broadening. While slower digestion rate usually means higher residual starch, this is not always so; both digestion parameters must be considered separately. The treatment shows that digestion kinetics depend on amylose content and also amylose molecular fine structure: the amount of shorter amylose chains and total amylose molecular size. The new combined data-treatment methodology is applicable to a wide range of food systems

High-amylose rice: starch molecular structural features controlling cooked rice texture and preference

Cooked high-amylose rices have slower digestibility, giving nutritional benefits, but inferior eating qualities. Molecular structural mechanisms for this inferior eating quality are found here using structural analysis by size-exclusion chromatography of both the parent starch and starch leached during cooking. All commonly-accepted sensory attributes of cooked rice were characterized by a trained human panel. Hardness, with the strongest negative correlation with panelist preference, was the dominant but not sole factor determining palatability. Hardness was controlled by the amounts of medium and long amylopectin chains and amylose in the starch, and by amylose content and amount of longer amylopectin chains in the leachate. This gives knowledge and understanding of the molecular structural characteristics of starch controlling cooked-rice preference: not just high amylose but also other aspects of molecular structure. This can help rice breeders to target starch-synthesis genes to select slowly digested (healthier) rices with acceptable palatability

Investigating cooked rice textural properties by instrumental measurements

Foods wherein the starch is slowly digested contribute to good health by reducing the tendency to, and for the maintenance of, diabetes, obesity and colo-rectal cancers. While foods with high amylose content have this desirable property, they usually do not have high sensory appeal and consumers are reluctant to eat them. While sensory evaluation by trained human panelists is the best way to obtain consumer preferences, these tests are expensive, time-consuming and require considerable effort and care. Instrumental measurements are easier, cheaper and invaluable for screening, but only useful if they correlate with human data for the type of food being considered. Here, we test this using cooked rice with a wide range of amylose contents. Functional properties were correlated against quantitative descriptive panelist analysis. Swelling power and breakdown viscosity correlated with all panelist sensory attributes, but no other correlations with gelatinization properties were observed. There was a strong correlation between hardness and stickiness measured by texture profile analysis (TPA) and by panelists, suggesting that TPA can be used to measure hardness and stickiness of cooked rice. We also showed that breakdown viscosity is a reliable instrumental means to provide indicative measurements of hardness and rice preference, and swelling power is a predictor of rice stickiness

How amylose molecular fine structure of rice starch affects functional properties

Starch molecular fine structure can have significant effects on pasting and thermal properties of rice flour. This study investigates the mechanistic explanation of these effects, by obtaining data for rice flour with different starch fine structures. Starch structural parameters for both amylose and amylopectin were obtained using size-exclusion chromatography (SEC, a type of gel-permeation chromatography, GPC), and the data fitted with methodologies (one of which is new) based on the underlying biosynthetic processes. It is found that the setback viscosity of rice starch measured by the rapid viscosity analyzer (RVA) depends not only on amylose content but also on the amount of long amylose chains and the size of whole amylopectin molecules. Conversely, long amylose chains and large amylopectin molecules are found to be responsible for the lower peak and trough viscosities. Other results for the effects of amylopectin chains are consistent with the literature. Mechanistic explanations for all observations are put forward. The novel findings about the influence of the distribution of amylose chain lengths and whole amylopectin size, in addition to amylose content alone, can provide guidance for rice breeders and food scientists in the selection of rices with improved functional properties

Starch Molecular Structural Features and Volatile Compounds Affecting the Sensory Properties of Polished Australian Wild Rice

Cooked high-amylose rices, such as Australian wild rice (AWR) varieties, have slower digestion rates, which is nutritionally advantageous, but may have inferior eating qualities. Here, a comparison is made between sensory and starch molecular fine structure properties, and volatile compounds, of polished AWR varieties and some commercial rices (CRs). Starch structural parameters for amylopectin (Ap) and amylose (Am) were obtained using fluorophore-assisted capillary electrophoresis and size-exclusion chromatography. Volatile compounds were putatively using headspace solid-phase microextraction with gas chromatography-mass spectrometry. Sensory properties were evaluated by a trained panel. AWR had a disintegration texture similar to that of Doongara rice, while AWR had a resinous, plastic aroma different from those of commercial rice varieties. Disintegration texture was affected by the amounts of Ap short chains, resinous aroma by 2-heptenal, nonadecane, 2h-pyran, tetrahydro-2-(12-pentadecynyloxy)-, and estra-1,3,5(10)-trien-17β-ol, and plastic aroma by 2-myristynoyl pantetheine, cis-7-hexadecenoic acid, and estra-1,3,5(10)-trien-17β-ol. These findings suggest that sensory properties and starch structures of AWR varieties support their potential for commercialization