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Glass transitions in starch, gluten and bread as measured

Dielectric spectroscopy and TMA methods

Journal of Thermal Analysis and Calorimetry
Authors: V. T. Huang, L. Haynes, H. Levine, and L. Slade

Dielectric Spectroscopy (DS) and Thermomechanical Analysis (TMA) were used to identity the glass transition temperature (T g) of native wheat starch, vital wheat gluten and a commercial bread, in response to changes in moisture content. An open-ended coaxial probe technique was used to measure the permittivity or dielectric constant (ɛ′) and the loss factor (ɛ″) as functions of moisture, for 2.45 GHz frequency, at constant density and temperature. Plots of ɛ′ and ɛ″ as functions of moisture content showed dramatic changes in mobility-based dielectric properties, which occur upon transition from the glassy solid to the rubbery liquid state. The modified TMA method can measure the change in viscoelastic properties aroundT g. This study further confirms that synthetic polymer science principles can be applied to food systems.

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The purpose of this study was to measure the effect of co-lyophilized polymers on the crystallization of amorphous sucrose, and to test for a possible relationship between the ability of an additive to raise theT g of a sucrose-additive mixture, relative to theT g of pure sucrose, and its ability to inhibit crystallization. Differential scanning calorimetry was used to measure the glass transition temperature,T g, the non-isothermal crystallization temperature,T c, and the induction time for crystallization,Q, of sucrose in the presence of co-lyophilized Ficoll or poly(vinylpyrrolidone) (PVP). The effect of these polymers on the crystallization of sucrose was significant as demonstrated by a marked increase inT c, and in the induction time (Q) in the presence of relatively small amounts (1–10%) of additive. Surprisingly, small amounts of polymeric additive had no effect on theT g of sucrose, although at higher concentrations, theT g increased proportionally. Thus, it appears that the inhibition of sucrose crystallization by the additition of small amounts of a higher-T g component cannot be attributed solely to changes in molecular mobility associated with an increase inT g.

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Soil seed banks can act as an important source in forest regeneration, and the information on the seed bank composition is vital for determining the resilience of plant communities under severe environments such as urban settings. In this study, we examined the seed bank density and functional composition, and their relationships with aboveground vegetation in three remnant evergreen broad-leaved forests, i.e., PuGang (PG), LuoGang (LG), and DaLingShan (DLS) under urbanization in Guangzhou, South China. In both years of our study (2010–2011), seed density and species richness for overall soil seed banks and each classified life forms (tree, shrub, herb and grass) significantly differed among the forests and were much higher in the PG forest. The prevailing life forms in the seed banks were herbs and grasses, and the proportion of tree species Importance Value index (IV) of the seed banks was low. We did not detect significant difference in the percentage of exotic species seeds in the seed banks among the forests. The proportion of species with animal dispersal mode was much higher in the DLS forest than in the PG and LG forests. The similarity in species composition between standing vegetation and seed banks was low with the lower value in the DLS forest than in PG and LG forest. Our findings suggest that the regeneration potential of the soil seed banks is limited for the remnant forests in urban areas. Therefore, greater proactive and enhanced conservation efforts are thus needed.

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An accurate and rapid liquid chromatography–electrospray ionizaion– tandem mass spectrometry (LC—ESI—MS/MS) analytical method was developed and validated for the simultaneous determination of antcins A, B, C, H, and K, dehydroeburicoic acid, and 4,7-dimethoxy-5-methyl-1,3-benzodioxole in the extract and capsule of Antrodia cinnamomea (AC) fruiting body. These seven signature compounds were ionized using an electrospray ion source and analyzed by a triple-quadrupole mass analyzer under a multiple reaction monitoring (MRM) mode. The MRM transitions of m/z 453/409 (antcin A), m/z 467/408 (antcin B), m/z 469/425 (antcin C), m/z 485/413 (antcin H), m/z 487/407 (antcin K), m/z 467/337 (dehydroeburicoic acid), and m/z 197/139 (4,7-dimethoxy-5-methyl-1,3-benzodioxole) were used to quantify these seven components, respectively. Their calibration curves presented good linear regressions (R 2 > 0.997) within the tested concentration range. The intra- and inter-day precisions were less than 1.97% and 2.53%, respectively. The overall recovery was in the range of 87.55%–95.41%. This validated high-performance liquid chromatography (HPLC)—MS/MS method offers promising applications for the accurate and rapid quantification of signature compounds in the fruiting body and its commercial products.

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Abstract  

The thermal mechanical properties and degradation behaviors were studied on fibers prepared from two high-performance, heterocyclic polymers, poly(p-phenylenebenzobisthiazole) (PBZT) and poly(p-phenylenebenzobisoxazole) (PBZO). Our research demonstrated that these two fibers exhibited excellent mechanical properties and outstanding thermal and thermo-oxidative stability. Their long-term mechanical tensile performance at high temperatures was found to be critically associated with the stability of the C—O or C—S linkage at the heterocyclic rings on these polymers' backbones. PBZO fibers with the C—O linkages displayed substantially higher thermal stability compared to PBZT containing C—S linkages. High resolution pyrolysis-gas chromatography/mass spectrometry provided the information of the pyrolyzates' compositions and distributions as well as their relationships with the structures of PBZT and PBZO. Based on the analysis of the compositions and distributions of all pyrolyzates at different temperatures, it was found that the thermal degradation mechanisms for both of these heterocyclic polymers were identical. Kevlar®-49 fibers were also studied under the same experimental conditions in order to make a comparison of thermo-oxidative stability and long-term mechanical performance at high temperatures with PBZO and PBZT fibers. The data of two high-performance aromatic polyimide fibers were also included as references.

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Cereal Research Communications
Authors: D. Huang, H. Zhang, M. Tar, Y. Zhang, F. Ni, J. Ren, D. Fu, L. Purnhauser, and J. Wu

Stripe or yellow rust (Yr), caused by Puccinia striiformis Westend. (Pst), is one of the most important wheat diseases worldwide. New aggressive Pst races can spread quickly, even between countries and continents. To identify and exploit stripe rust resistance genes, breeders must characterize first the Pst resistance and genotypes of their cultivars. To find new sources of resistances it is important to study how wheat varieties respond to Pst races that predominate in other continents. In this study we evaluated stripe rust resistance in 53 Hungarian winter wheat cultivars in China. Twenty-four cultivars (45.3%) had all stage resistance (ASR) and 1 (1.9%) had adult-plant resistance (APR), based on seedling tests in growth chambers and adult-plant tests in fields. We molecularly genotyped six Yr resistance genes: Yr5, Yr10, Yr15, Yr17, Yr18, and Yr36. Yr18, an APR gene, was present alone in five cultivars, and in ‘GK Kapos’, that also had seedling resistance. The other five Yr genes were absent in all cultivars tested.

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Biofortifying food crops with essential minerals would help to alleviate mineral deficiencies in humans. Detection of quantitative trait loci (QTLs) for mineral nutrient contents in rice was conducted using backcross inbred lines derived from an interspecific cross of Oryza sativa × O. rufipogon. The population was grown in Hangzhou and Lingshui, with the contents of Mg, Zn, Fe, Mn, Cu and Se in brown rice measured in both trials and that in milled rice tested in Hangzhou only. A total of 24 QTLs for mineral element contents were identified, including two for both the brown and milled rice, 17 for brown rice only, and five for milled rice only. All the seven QTLs detected for the mineral contents in milled rice and 13 of the 19 QTLs for the contents in brown rice had the enhancing alleles derived from O. rufipogon. Fifteen QTLs were clustered in seven chromosomal regions, indicating that common genetic-physiological mechanisms were involved for different mineral nutrients and the beneficial alleles could be utilized to improve grain nutritional quality by markerassisted selection.

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Journal of Thermal Analysis and Calorimetry
Authors: F. Xu, L. Sun, J. Zhang, Y. Qi, L. Yang, H. Ru, C. Wang, X. Meng, X. Lan, Q. Jiao, and F. Huang

Abstract  

Heat capacities of the carbon nanotubes (CNTs) with different sizes have been measured by modulated temperature differential scanning calorimetry (MDSC) and reported for the first time. The results indicated the values of C p increased with shortening length of CNTs when the diameters of CNTs were between 60 and 100 nm. However, the values of C p of CNTs were not affected by their diameter when the lengths of CNTs were 1–2 um, or not affected by the length of CNTs when their diameters were below 10 nm. The thermal stabilities of the CNTs have been studied by TG-DTG-DSC. The results of TG-DTG showed that thermal stabilities of CNTs were enhanced with their diameters increase. With lengths increase, the thermal stabilities of CNTs increased when their diameters were between 60 and 100 nm, but there is a slight decrease when their diameters were less than 60 nm. The further DSC analyses showed both released heat and T onset increased with the increase of CNTs diameters, which confirms the consistency of the results from both TG-DTG and DSC on CNTs thermal stability.

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Abstract  

To investigate the effects of lanthanum exposure on regional distribution of inorganic elements in rat brain. Wistar rats were exposed to lanthanum chloride through oral administration at 0, 0.1, 2, and 40 mg/kg concentration for 6 months. The elements such as Cl, K, Ca, Fe, Cu, and Zn were identified in the brain slices by synchrotron radiation X-ray fluorescence (SRXRF) analysis. Differences of brain elemental distributions were noticed. Cl, Ca, and Zn were primarily concentrated in hippocampus of the controls. With the increase of the lanthanum dosage, the Ca and Zn levels significantly decreased, while the Cu levels significantly elevated in cortex, hippocampus and thalamus. Our results suggest that subchronic lanthanum exposure in rats appears to change elemental distributions in brain.

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Bee pollen is a health food with a wide range of nutritional and therapeutic properties. However, the bioactive compounds of bee pollen have not been extensively revealed due to low efficacy in separation. High-speed counter-current chromatography (HSCCC) and solvent extraction were applied to separate tyrosinase inhibitors from camellia pollen in this study. The camellia pollen extracts prepared with petroleum ether, ethyl acetate, and n-BuOH have tyrosinase inhibitory activity. Acidic hydrolysis could promote the tyrosinase inhibitory activity of crude sample. Three fractions with tyrosinase inhibitory activity were separated from the hydrolysate by a one-step HSCCC procedure. Among the fractions, two chemicals were sufficiently purified and identified to be levulinic acid (LA) and 5-hydroxymethylfurfural (5-HMF). The recovery was 0.80 g kg−1 pollen for LA and 1.75 g kg−1 pollen for 5-HMF; and their purity was all over 98%. The study demonstrates that HSCCC method is powerful for preparative separation of tyrosinase inhibitors from camellia pollen.

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