Effect of CaCO3 contents on the properties of polyethylene nanocomposites sheets

Nanocomposites of high-density polyethylene/linear low-density polyethylene (HDPE/LLDPE) filled with untreated and surface treated nano-calcium carbonate (nCC) were prepared. The influence of isopropyl tri-(dioctylpyrophosphato) titanate (JN114) treatment of nCC on the morphology, mechanical, crystallization and flow properties of the nanocomposites were studied. The results of scanning electron microscopy (SEM) showed that JN114 treated nCC was better dispersion in the matrix than the untreated one. A fine dispersion of the treated nanoparticles in the nanocomposites was observed by transmission electron microscopy (TEM). The FTIR spectrum analysis revealed that the JN114 could change the surface properties of nCC, resulting in greater hydrophobicity of the surface and enhanced compatibility with nonpolar matrices. The tensile elastic modulus (E _c ) and Izod impact strength (SIC) of nanocomposites increased with the increasing of nCC content while tensile fracture strength (σ _b ) decreased. The JN114 treated nanocomposites had superior mechanical properties to those of the untreated ones. The compatibility of these nanocomposites was examined by DSC to estimate melting point (T _m ) and crystallization temperature (T _c ). Furthermore, the melt flow index (MFI) of the nanocomposite materials were measured. It was found that the MFI decreased with the addition of weight fraction of the nCC particles.     

Water vapor transport parameters of a cast wheat gluten film

Understanding the mode of transport of water vapor through the film is important for improving the moisture barrier properties of wheat gluten (WG) films. Effective permeability (P_eff), solubility (S_eff), and diffusion (D_eff) coefficients of a hydrophilic cast WG film were determined at 25°C within the relative humidity (RH) range of 0–84% (with a 9–13% RH gradient between upstream and downstream water vapor flux). P_eff, S_eff, and D_eff increased substantially as the RH gradient moved upwards in the RH spectrum. P_eff increased by four orders of magnitude from the lowest RH condition of 0–11% (3.8×10⁻¹¹ g·m/m²·s·Pa) to the highest RH condition of 75–84% (4.1×10⁻⁷ g·m/m²·s·Pa). A moisture sorption isotherm of the film at 25°C was constructed. Both the Guggenheim–Anderson–DeBoer (GAB) and the Kuhn moisture sorption isotherm models showed a good fit to the experimental adsorption data. Testing of WG films at the expected conditions of actual use is necessary to quantify the water vapor permeation through the films.     

Physicochemical and antioxidant properties of extruded corn grits with corn fiber by CO2 injection extrusion process

Corn grits and corn fiber mixed at different mass ratios (0/100, 15/85 and 30/70) were extruded at different melt temperature (90, 105 and 120 °C) using extrusion with and without CO₂ injection. The L value, reducing sugar content and antioxidant properties decreased after extrusion with or without CO₂ injection. The color and antioxidant properties were relatively stable in the extrusion with CO₂ injection at higher melt temperature (120 °C) in comparison with the extrusion without CO₂ injection. Higher corn fiber content resulted in less loss of total phenolic content. The b, ΔE values and water absorption index increased after extrusion. The increase of the water absorption index was higher after the extrusion process with the CO₂ injection especially at the lower melt temperature. The addition of corn fiber decreased L, b, and ΔE values, but significantly increased antioxidant properties under the same extrusion conditions.     

Dynamic water vapour sorption in gluten and starch films

Water sorption of gluten and wheat starch films as a function of water activity was studied using gravimetric step-change sorption experiments. Films of different thicknesses were used with the aim to vary the characteristic diffusion time and to get insights in the contribution of the polymer-chain rearrangement in the sorption behaviour. It is shown that both starch and gluten are in the glassy state for a water activity a_w below 0.9. From comparison of the dynamical sorption curves with a Fickian diffusion model, it is shown that water diffusion in gluten films seems Fickian for a_w < 0.7, and non-Fickian for a_w > 0.7, while for starch films, non-Fickian sorption behaviour is observed for a_w > 0.1. The results show that polymer-chain rearrangement and the stress built up in the matrix play an important role in the sorption dynamics of these films. Even when the material is in the glassy state matrix relaxation phenomena play a role in the sorption behaviour of starch and gluten.     

Effects of laccase,xylanase and their combination on the rheological properties of wheat doughs

The effects of Trametes hirsuta laccase alone and in combination with Aspergillus oryzae and Bacillus subtilis xylanases on dough extensibility were studied using the Kieffer test to determine the dough extensibility (E_x) and the resistance to stretching (R_max). Laccase treatment resulted in dough hardening: the R_max of dough increased and the E_x at R_max decreased as a function of dosage (5–50 nkat/g flour). Xylanases softened flour and gluten doughs. Hardening by laccases and softening by xylanases was weaker in gluten doughs. Dough hardening, observed in the laccase treatments, decreased as a function of dough resting time. The softening effect occurred especially at higher laccase dosages (≈50 nkat/g flour). The softening phenomenon was related to the laccase-mediated depolymerization of the cross-linked AX network. In combined laccase and xylanase treatments, the effect of laccase was predominant, especially at low xylanase dosage, but when xylanase was added to flour dough at high concentrations, the hardening effect of laccase on dough was decreased. In combined laccase and xylanase treatments in gluten doughs, similar decreases in laccase-mediated hardening were not seen.     

Substrate selectivity and inhibitor sensitivity affect xylanase functionality in wheat flour gluten–starch separation

Addition of xylanases (EC 3.2.1.8) that varied in their substrate selectivities and/or wheat xylanase inhibitor sensitivities in dough batter gluten–starch separation of wheat flour showed the importance of these enzyme characteristics for their functionality in this process. A xylanase from Aspergillus aculeatus (XAA) with selectivity for hydrolysis of water extractable arabinoxylan (WE-AX), which is not inhibited by wheat flour xylanase inhibitors decreased batter viscosity and improved gluten agglomeration behaviour. In contrast, a xylanase from Bacillus subtilis (XBS_i) with selectivity for hydrolysis of water unextractable arabinoxylan (WU-AX), which is in vitro inhibited by wheat flour xylanase inhibitors had a negative effect on gluten agglomeration at low enzyme dosages. As expected, solubilisation of WU-AX increased batter viscosities. At higher dosages however, this enzyme also improved gluten agglomeration because of degradation of both WE-AX and enzymically solubilised AX. A mutated B. subtilis xylanase (XBS_ni) with selectivity for hydrolysis of WU-AX comparable to XBS_i but which is not inhibited by wheat flour xylanase inhibitors, increased the level of large gluten aggregates as well as the total gluten protein recovery, even at lower dosages. Because of its inhibitor insensitivity, the solubilisation and degradation of AX proceeded further. An XBS_ni dosage approximately 4 times lower than XBS_i performed as well as its inhibited counterpart. The degradation of both WE-AX and WU-AX by XBS_ni improved the gluten agglomeration behaviour to a larger extent than the XAA treatment which primarily resulted in hydrolysis of WE-AX. The results confirm the detrimental impact not only of WE-AX, but also of WU-AX, on gluten agglomeration in a dough batter gluten–starch separation process. At the same time, they provide firm evidence that xylanases are not only inhibited by xylanase inhibitors in vitro, but are also partly inhibited in the industrial process in which they are used.     

Elasticity, microstructure and thermal stability of foliage and fruit fibres from four tropical crops

A comparative analysis of the elasticity, microstructure and thermal stability of fibres (thickness ranging from 43.4 to 189.4 µm) isolated from pineapple leaves (PALF), coconut coir (COIR), banana leaf-stem (BAN) and oil palm empty fruit bunch (OPEFB) reported in this study. Statistical analysis of the mechanical properties derived from tensile test to rupture reveals significant differences (P<0.05) in the fibre strength (σ), stiffness (E) and extensibility (parameterized by the strain to rupture, ?). It is observed that COIR fibres yield the smallest strength, σ (=99.8±22.5 MPa), and stiffness, E (= 0.5±0.1 GPa), while PALF fibres yield the largest σ (=639.5±301.6 MPa) and E (=7.1±3.1 GPa); PALF fibres exhibit the smallest ? (=0.11±0.03) but OPEFB fibres yield the largest ? (=2.0±1.3). From scanning electron micrographs, it is observed that cellulose fibril rupture predominates in OPEFB, COIR and BAN fibres; a large proportion of the cellulose fibrils fail by pullout in PALF fibres. Thermogravimetric analysis reveals that all fibres are thermally stable up to 250 °C; the fibre residue ranges from 30 to 80 wt% after heating to 500 °C. In particular, BAN experiences the highest weight loss and PALF experiences the lowest weight loss. The findings lend to a simple approach for determining the performance of the composites by assessing the type of natural fibres for reinforcing polymeric matrices.     

New B low Mr glutenin subunit alleles at the Glu-A3, Glu-B2 and Glu-B3 loci and their relationship with gluten strength in durum wheat

The B low M_r subunits of glutenin of the F₂ generation from three durum wheat crosses were analysed. Three new alleles were found at three different loci: Glu-A3i coding for 5+20 subunits, Glu-B2c coding for subunit 12* and Glu-B3l coding for 1+3+13*+16 subunits. The genetic distances between Glu-A3-Gli-A1, Glu-B2-Gli-B1, Glu-B3-Glu-B2 and Glu-B3-Gli-B1 were calculated. The effects of the allelic variation at the Glu-A3, Glu-B2 and Glu-B3 on protein content and gluten strength, as measured by the SDS-sedimentation test, were determined using F₄ lines from the three crosses. All the new alleles affected significantly gluten strength. The presence of Glu-A3i had a negative influence on SDSS values compared with the allele a. For Glu-B2 and Glu-B3 the data obtained enable the effects of the alleles on SDSS volume to be ranked: a=b>c for Glu-B2 and a>b>l for Glu-B3. The results also shown that the allelic variants at Glu-B3 had a much greater effect on gluten strength than the variants at Glu-A3 or Glu-B2 loci. A high percentage of variation in sedimentation volume was explained by the prolamins (52 and 70%).     

安徽麦区软质小麦籽粒品质和终端制品品质评价

为明确安徽大田生产环境下软质小麦籽粒和终端产品品质表现,评价优质软麦品种的加工适用性,本研究选取该区当前推广种植的24个软质小麦品种,对其籽粒和面粉的主要品质性状及其制品南方馒头和曲奇饼干的品质进行差异性、相关性分析,并以美国软白麦近五年的主要品质性状平均值为理想指标进行灰色关联度比较。结果表明,供试材料的硬度、面粉色泽b^*、湿面筋含量、面团形成时间、稳定时间等籽粒品质性状变异系数较大,而容重、面粉L^*值和吸水率变异系数较小。南方馒头品质性状中,白度差异最小,比容差异最大;曲奇饼干品质性状中,感官评分变异系数较大,饼干直径均值和变异系数都较小。蛋白质含量、湿面筋含量、稳定时间均符合弱筋标准(GB/T 17320-2013)的样品数为0。相关分析表明,容重、降落值、面粉L^*、b^*、白度与大部分性状间相关性不显著;籽粒硬度与水SRC和乳酸SRC均呈显著正相关,与湿面筋含量和面粉a^*值均呈显著负相关。蛋白质含量与面粉a^*值等7个指标均呈显著正相关,与面粉b     

Effect of temperature and time on mechanical and electrical properties of HDPE/glass fiber composites

In recent years, composites based on glass fiber reinforced polymer have been widely used in order to meet increasing durability and safety regulations, particularly in the power cable, automotive and plane industry. In this paper, mechanical and electrical properties of high density polyethylene (HDPE) and HDPE containing glass fiber polymer composites were investigated and compared at different temperatures. Composite materials were prepared with the hot pressing method. Tensile strength, % elongation and the modulus of elasticity (or Young’s modulus) were determined for each sample at different temperatures. In addition to this, at different temperatures τ _σ and τ _E have mechanical and electrical lifetime respectively, corresponding to mechanical tension (σ) and electrical strength (E), and this was investigated for each sample. As compared to the mechanical and electrical properties of neat HDPE, HDPE/0.5 % glass fiber composites have been found to have better mechanical and electrical durability.     

Thermal stability of wheat gluten protein: its effect on dough properties and noodle texture

There is a need to develop more sensitive and reliable tests to help breeders select wheat lines of appropriate quality. Gluten thermostability, measured by the viscoelasticity of heated gluten, was assessed for its usefulness in evaluating quality of wheats in breeding programs. Two sets of wheat samples were used: Set I consisting of 20 cultivars and/or breeders' lines (BL), with diverse dough strengths and allelic variations of high M_r glutenin subunits coded at the Glu-A1, Glu-B1 and Glu-D1 loci (N=20) and Set II consisting of 16 near isogenic BL of F7 generation that had been in a quality selection program for three years. Thermostability of the isolated wet gluten was determined by measuring its viscoelastic properties, and was related to noodle texture, flour protein content, protein composition, dough physical properties and other quality predicting tests.Viscoelasticity of heat-treated gluten, isolated with 2% NaCl solution, significantly correlated with most of the tests used to measure dough and/or gluten strength and Chinese white salted noodle texture. The rate of thermal denaturation of proteins depends on M_r and packing density. High ratios of monomeric proteins such as gliadins and low M_r glutenin subunits to high M_r glutenin subunits increase the thermostability of the gluten. The measurement of viscoelasticity of heat-denatured gluten can be a useful test to determine gluten quality. Our study showed that gluten viscoelasticity and most of the tests related to dough and/or gluten strength are independent of allelic variations of the high molecular weight glutenin subunits. This test has been developed for predicting white salted noodle quality.     

Effects of N and K fertilizers on durum wheat quality in different environments

Eight genotypes from two different genetic pools (high yielding varieties and landraces) were assessed for grain yield (GY) and for five quality traits: protein content (P), thousand kernel weight (TKW), yellow berry (YB), gluten content (G_c) and gluten index (G_i) in sub-humid and semi-arid areas using four combinations of nitrogen and potassium fertilizers during two cropping seasons. Genotype × Environment × Fertilizers (G × E × F) was significant only for protein content (p < 0.05); and E × F was found significant (p < 0.05) for all parameters. Greater quality related traits expression was noted in the semi-arid areas for both genetic pools. Excessive rainfall in semi-arid areas resulted in gluten elasticity reduction. N-fertilizers seemed to enhance protein content and to reduce thousand kernel weight. K-fertilizer, might enhance the increase in both proteins and thousand kernel weight in favorable growing conditions of water availability. Semolina yielding ability was higher in landraces as compared to high yielding varieties particularly using recommended fertilizer management. This group of cultivars showed superiority over high yielding cultivars for quantitative quality parameters.     

Water mobility,rheological and textural properties of rice starch gel

Three rice starches from indica (TNuS19), japonica (TNu67) and waxy (TCW70) were used as samples to investigate the water mobility, viscoelasticity and textural properties of starch gels using pulsed nuclear magnetic resonance (PNMR), dynamic rheometer and texture analyzer. The spin–spin relaxation time (T₂), showed water mobility of starch gels was detected with starch concentrations 10–30%. Generally, the TNuS19 and TNu67 at ≥20% showed two components (T_2a and T_2b) in water mobility, where T_2a and T_2b related to solid-like and liquid-like water molecules in starch gels, respectively. However, the TCW70 over the concentrations examined had only T_2b component, higher than those of corresponding TNuS19 and TNu67. The storage (G′) and loss (G″) moduli of starch gels were in the order of TNuS19 > TNu67 > TCW70. Texture analyzer analysis indicated that TNuS19 had higher hardness, stickiness and adhesiveness than did the TNu67 and TCW70, and changed significantly with the starch concentration increase. The value of T_2b was highly correlated with physical properties of starch gels, especially with dynamic rheological parameters. It is suggested that amylose content may play a major role to influence the water mobility of starch gels which affects the specific viscoelasticity and textural properties of starch gels.     

Large deformation stress relaxation and compression-recovery of gluten representing different wheat classes

Despite the great variety of physicochemical and rheological tests available for measuring wheat flour, dough and gluten quality, the US wheat marketing system still relies primarily on wheat kernel hardness and growing season to categorize cultivars. To better understand and differentiate wheat cultivars of the same class, the tensile strength, and stress relaxation behavior of gluten from 15 wheat cultivars was measured and compared to other available physicochemical parameters, including but not limited to protein content, glutenin macropolymer content (GMP) and bread loaf volume. In addition, a novel gluten compression–relaxation (Gluten CORE) instrument was used to measure the degree of elastic recovery of gluten for 15 common US wheat cultivars. Gluten strength ranged from 0.04 to 0.43 N at 500% extension, while the degree of recovery ranged from 5 to 78%. Measuring gluten strength clearly differentiated cultivars within a wheat class; nonetheless it was not a good predictor of baking quality on its own in terms of bread volume. Gluten strength was highly correlated with mixograph mixing times (r = 0.879) and degree of recovery (r = 0.855), suggesting that dough development time was influenced by gluten strength and that the CORE instrument was a suitable alternative to tensile testing, since it is less time intensive and less laborious to use.     

Effects of ultrasound-assisted freezing on the water migration of dough and the structural characteristics of gluten components

The effects of ultrasound-assisted freezing on the freezing time and water migration of dough, and the structural characteristics of gluten components were investigated. The effects of ultrasound-assisted freezing in the whole immersion freezing process (UWF) on the freezing time were better than those of ultrasound-assisted freezing in the maximum ice crystal generation zone. The shortest freezing time was obtained at 80 W/L, and was 577 s shorter than that with traditional immersion freezing. The UWF treatment at 80 W/L significantly (p < 0.05) affected the absorption enthalpy, freezable water content and water migration of frozen dough. In UWF compared with traditional immersion freezing, the SH content of gluten, glutenin and gliadin was significantly (p < 0.05) higher, by 12.06%, 27.55% and 21.65%, respectively. The surface hydrophobicity of gluten, glutenin and gliadin in UWF treated samples significantly (p < 0.05) decreased, by 19.67%, 13.21% and 9.17%, respectively. The secondary structure of gluten components was also significantly changed by UWF. The network of gluten, the chain structure of glutenin and the gliadin particles were all changed by UWF treatment. These findings indicated that UWF is an effective method to improve the moisture distribution in dough and reduce the damage to protein molecular structure caused by freezing.     

Mechanical and Dynamic Mechanical Studies on Epoxy-Cobaltous Sulfate Polymer Hybrids

Cobaltous sulfate heptahydrate (CoSO₄·7H₂O) was incorporated as filler into diglycidyl ether of bisphenol A (DGEBA) based epoxy resin system, to prepare organic-inorganic polymer hybrid materials. Mechanical tensile studies and dynamic mechanical analysis (DMA) were carried out in order to study the static and dynamic mechanical properties of the prepared hybrid films. Mechanical tensile studies were carried out at room temperature, at a test speed of 30 mm/min. Highest tensile strength of 24.74±2.42 MPa was achieved for 4.44 wt% filler level (FL), along with an increase in the value of Young’s modulus. Storage modulus (E′), loss modulus (E″), damping factor (tan δ) were obtained by DMA studies. Glass transition temperature (T_g) was obtained for pure epoxy and filled epoxy, for various FLs varying from 0.28 wt% to 5.00 wt%. Pure epoxy showed highest T_g value compared to filled epoxy hybrids. Highest storage modulus of 9.5 GPa was obtained for 2.22 wt% FL, which also showed highest loss modulus peak. Parameters like effectiveness coefficient (C) and crosslink density were calculated from the storage modulus data. Loss modulus and tan δ curves were analyzed to study the energy dissipation properties of prepared hybrid films. Activation energy (E_a) value for glass transition was obtained from damping factor (tan δ), which showed highest E_a value of 630.5 kJmol^-1, for 4.44 wt% FL. DMA studies for various FLs were carried out at different test frequencies in order to study the changes in dynamic mechanical properties of the prepared hybrid materials with respect to frequency     

河北省主要推广强筋小麦的面包加工品质

为了解河北省主推强筋小麦品种的籽粒品质和面包加工品质,评选优质面包小麦品种,对河北省9个强筋小麦品种的31个籽粒品质和8个面包加工品质指标进行了测定。结果表明,除千粒重、容重、籽粒硬度、出粉率、面粉色泽L*值、面粉色泽b*值、面粉白度、籽粒蛋白质含量、湿面筋含量、糊化温度、吸水率外,其余被测指标的变异系数均大于10%,说明河北省强筋小麦品种多数品质性状的遗传多样性比较丰富。藁优9415、冀师02-1、藁优2018和金麦1号4个小麦品种制作的面包达到国家优质面包标准。面包评分与面团拉伸曲线面积和最大拉伸阻力极显著正相关,与形成时间、稳定时间、粉质质量指数、延伸度和拉伸阻力显著正相关,与面包质构的粘聚性极显著正相关,与面包质构的硬度、胶着性、咀嚼度、坚实度均极显著负相关。     

Effect of allelic variation at the Glu-3/Gli-1 loci on breadmaking quality parameters in hexaploid wheat (Triticum aestivum L.)

Low molecular weight glutenin subunits (LMW-GS) encoded by the Glu-3 loci are known to contribute to wheat breadmaking quality. However, the specific effect of individual Glu-3 alleles is not well understood due to their complex protein banding patterns in SDS-PAGE and tight linkage with gliadins at the Gli-1 locus. Using DNA markers and a backcross program, we developed a set of nine near isogenic lines (NILs) including different Glu-A3/Gli-A1 or Glu-B3/Gli-B1 alleles in the genetic background of the Argentine variety ProINTA Imperial. The nine NILs and the control were evaluated in three different field trials in Argentina. Significant genotype-by-environment interactions were detected for most quality parameters indicating that the effects of the Glu-3/Gli-1 alleles are modulated by environmental differences. None of the NILs showed differences in total flour protein content, but relative changes in the abundance of particular classes of proteins cannot be ruled out. On average, the Glu-A3f, Glu-B3b, Glu-B3g and Glu-B3i_Man alleles were associated with the highest values in gluten strength-related parameters, while Glu-A3e, Glu-B3a and Glu-B3i_Chu were consistently associated with weak gluten and low quality values. The value of different Glu-3/Gli-1 allele combinations to improve breadmaking quality is discussed.     

减少灌水量对强筋小麦花后干物质和氮素积累、转运及产量的影响

为探究灌水量对强筋小麦花后干物质和氮素积累、转运及产量的影响,选用强筋小麦品种中麦998和中麦1062,在防雨棚池栽条件下,春季于拔节期和开花期灌水,每时期设600（W₆₀₀）、300（W₃₀₀）和0 m·hm^-2（W₀）3个灌水量处理,研究了减少灌水量对强筋小麦花后干物质含量、氮素积累和转运、籽粒产量、籽粒蛋白质含量和产量的影响。结果表明,随春季灌水量的减少,强筋小麦植株干物质积累量、氮素积累量、粒重比、叶重比、籽粒产量和蛋白质产量均表现为下降趋势,而蛋白质含量和水分利用效率呈上升趋势。两品种叶片氮素转运量和氮素转运效率以W₃₀₀处理下最高,且叶片氮素转运效率在W₃₀₀和W₆₀₀处理之间均无显著差异。中麦1062在W₀和W₃₀₀处理下水分利用效率无显著差异,中麦998在W₃₀₀和W₆₀₀处理下蛋白质含量无显著差异。综上可见,W₃₀₀处理既能有效提高强筋小麦花后干物质转运量,维持较高的产量和水分利用效率,同时又能提高氮素转运量和籽粒蛋白质含量,达到节水高产的目的。     

Depolymerisation and Re-polymerisation of Wheat Glutenin During Dough Processing. I. Relationships between Glutenin Macropolymer Content and Quality Parameters

The protein content and the content of protein-related parameters of both flour and dough were related to the maximum resistance (R_max) and extensibility (E) of dough, as determined in a Brabender Extensograph, and to loaf volume. The glutenin macropolymer (GMP) content of flour and dough was more strongly related toR_maxthan protein content or the content of the group of Osborne fractions (glutenin, gliadin, albumin/globulin). Within each group of protein-related parameters, the contents of the Osborne glutenin fractions explained the variation in all quality parameters better than the contents of the gliadin or albumin/globulin fraction. The GMP content of dough after 45 min rest was more strongly related toR_max, whereas the GMP content of flour was more strongly related toEand loaf volume. This demonstrates that, during mixing and resting of dough, changes occur in the GMP that are important forR_maxbut not forEor loaf volume. Although limited numbers of wheat cultivars (15), harvest years (2), flour blends (8) and resting times (3) were investigated, the relationship between the GMP content of dough andR_maxwas independent of these variables.