Effect of stirring and seeding on whey protein fibril formation

The effect of stirring and seeding on the formation of fibrils in whey protein isolate (WPI) solutions was studied. More fibrils of a similar length are formed when WPI is stirred during heating at pH 2 and 80 degrees C compared to samples that were heated at rest. Addition of seeds did not show an additional effect compared to samples that were stirred. We propose a model for fibril formation, including an activation, nucleation, growth, and termination step. The activation and nucleation steps are the rate-determining steps. Fibril growth is relatively fast but terminates after prolonged heating. Two processes that possibly induce termination of fibril growth are hydrolysis of nonassembled monomers and inactivation of the growth ends of the fibrils. Stirring may break up immature fibrils, thus producing more active fibrils. Stirring also seems to accelerate the kinetics of fibril formation, resulting in an increase of the number of fibrils formed.     

Re-formation of fibrils from hydrolysates of β-lactoglobulin fibrils during in vitro gastric digestion

In this study, in vitro digestion of β-lactoglobulin (β-Lg) fibrils and the re-formation of fibril-like structures after prolonged enzymatic hydrolysis (up to 48 h) were investigated using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), thioflavin T fluorescence photometry, and transmission electron microscopy (TEM). Pure β-Lg fibrils that had been formed by heat treatment at pH 2.0 were rapidly hydrolyzed by pepsin in the simulated gastric fluid (pH 1.2), and some new peptides that were suitable for further fibril formation were produced. TEM showed that the new fibrils were long and straight but thinner than the original fibrils, and both TEM and MALDI-MS indicated that the peptides in the new fibrils were shorter/smaller than the peptides in the original fibrils. The formation of new fibrils was found to be affected more by pH than by enzyme activity or temperature.     

Effect of pH, NaCl, CaCl2 and temperature on self-assembly of β-lactoglobulin into nanofibrils: a central composite design study

The ability of certain globular proteins to self-assemble into amyloid-like fibrils in vitro opens opportunities for the development of new biomaterials with unique functional properties, like highly efficient gelation and viscosity enhancement. This work explored the individual and interacting effects of pH (1 to 3), NaCl (0-100 mM), CaCl(2) (0-80 mM) and heating temperature (80 to 120 °C) on the kinetics of β-lactoglobulin self-assembly and the morphology of resulting nanofibrils. Statistically significant (p < 0.05) interactions included CaCl(2)*temperature, NaCl*pH, CaCl(2)*pH, temperature*pH and NaCl*CaCl(2). Particularly notable was the very rapid self-assembly at pH 3 and the highly nonlinear effect of pH on self-assembly kinetics. Nanofibril morphologies ranged from long and semiflexible or curled and twisted to short and irregular. There did not seem to be a link between the kinetics of fibril formation and the morphology of fibrils, except at pH 3, where self-assembly was very rapid and fibrils were short and irregular, suggesting haphazard, uncontrolled self-assembly.     

Micrometer-sized fibrillar protein aggregates from soy glycinin and soy protein isolate

Long, fibrillar semiflexible aggregates were formed from soy glycinin and soy protein isolate (SPI) when heated at 85 degrees C and pH 2. Transmission electron microscopy analysis showed that the contour length of the fibrils was approximately 1 microm, the persistence length 2.3 microm, and the thickness a few nanometers. Fibrils formed from SPI were more branched than the fibrils of soy glycinin. Binding of the fluorescent dye Thioflavin T to the fibrils showed that beta-sheets were present in the fibrils. The presence of the fibrils resulted in an increase in viscosity and shear thinning behavior. Flow-induced birefringence measurements showed that the behavior of the fibrils under flow can be described by scaling relations derived for rodlike macromolecules. The fibril formation could be influenced by the protein concentration and heating time. Most properties of soy glycinin fibrils are comparable to beta-lactoglobulin fibrils.     

全膜双垄沟播一膜两茬栽培技术

为了实现节本增效,在灵台县采用了一膜两年用免耕栽培的方法,开展了全膜双垄沟播玉米收获后穴播冬油菜的生产模式研究,即在玉米成熟后,采用人工收获,清除玉米秸秆,保护好上茬地膜,在原地膜上穴播点种冬油菜,冬油菜产量可达3 080 kg/hm2,是一种轻简方便,高产高效的模式。     

Methionine oxidation enhances κ-casein amyloid fibril formation

The effects of protein oxidation, for example of methionine residues, are linked to many diseases, including those of protein misfolding, such as Alzheimer's disease. Protein misfolding diseases are characterized by the accumulation of insoluble proteinaceous aggregates comprised mainly of amyloid fibrils. Amyloid-containing bodies known as corpora amylacea (CA) are also found in mammary secretory tissue, where their presence slows milk flow. The major milk protein κ-casein readily forms amyloid fibrils under physiological conditions. Milk exists in an extracellular oxidizing environment. Accordingly, the two methionine residues in κ-casein (Met(95) and Met(106)) were selectively oxidized and the effects on the fibril-forming propensity, cellular toxicity, chaperone ability, and structure of κ-casein were determined. Oxidation resulted in an increase in the rate of fibril formation and a greater level of cellular toxicity. β-Casein, which inhibits κ-casein fibril formation in vitro, was less effective at suppressing fibril formation of oxidized κ-casein. The ability of κ-casein to prevent the amorphous aggregation of target proteins was slightly enhanced upon methionine oxidation, which may arise from the protein's greater exposed surface hydrophobicity. No significant changes to κ-casein's intrinsically disordered structure occurred upon oxidation. The enhanced rate of fibril formation of oxidized κ-casein, coupled with the reduced chaperone ability of β-casein to prevent this aggregation, may affect casein-casein interaction within the casein micelle and thereby promote κ-casein aggregation and contribute to the formation of CA.     

氮肥一次性基施对不同机直播水稻产量和品质的影响

为探索不同机直播方式下优质食味水稻氮肥一次性基施的轻简高效栽培技术,该研究以迟熟中粳南粳9108为材料,在水、旱2种机直播方式下,设置控释-速效氮肥配方A一次性基施处理（T1）、控释-速效氮肥配方B一次性基施处理（T2）和速效尿素定量分施处理（CK）,研究氮素一次性基施对2种机直播水稻产量和品质的影响及该施肥方式下不同机直播水稻产量和品质特征与差异。结果表明,产量方面,不同机直播水稻氮肥一次性基施处理产量均超过9.0 t/hm2,水直播稻产量由高到低的顺序为CK、T1、T2,其中CK与T1差异不显著,旱直播稻产量由高到低的顺序为CK、T2、T1,其中CK与T2差异不显著。同一施肥处理下,除T1处理的水直播稻产量显著高于旱直播外,其他处理的水、旱直播稻产量差异不显著。品质方面,与CK相比,氮肥一次性基施处理改善了稻米加工品质和营养品质,整精米率和蛋白质含量分别提高5.79%～12.21%、1.18%～3.86%;外观品质变差,垩白度增加0.16%～15.12%;直链淀粉含量降低1.14%～5.12%。水直播稻食味值T1与CK差异不显著,但均显著高于T2（P<0.05）,旱直播稻食味值在施肥处理间差异不显著。氮肥一次性基施处理的RVA谱特征值中峰值黏度、热浆黏度、最终黏度和崩解值较CK降低,消减值和回复值较CK增加。不同机直播方式间,水稻加工品质和外观品质无显著差异;直链淀粉含量由高到低的顺序为水直播、旱直播;蛋白质含量由大到小的顺序为旱直播、水直播,差异不显著;食味值差异不显著;崩解值由大到小的顺序为水直播、旱直播,差异显著（P<0.05）,消减值由大到小的顺序为旱直播、水直播,差异显著（P<0.05）,水稻淀粉RVA谱其他特征值差异不显著。综上,水直播方式下选用控释-速效氮肥配方A一次性基施,旱直播方式下选用控释-速效氮肥配方B一次性基施可实现水稻稳产并改善部分米质,且大幅度减少施肥次数,利于机直播稻轻简化优质稳产的高效生产。     

气吸式玉米高速精量排种器直线投种过程分析与试验

为解决气吸式玉米精量排种器在高速作业条件下投种过程种子与导种管碰撞异位造成排种粒距合格率下降和排种粒距变异系数增大的问题,该文提出了一种利用推种装置配合种盘吸孔实现直线投种的方法,并对直线投种原理进行分析,阐明直线投种过程中种子与排种器的运动和力学关系,明确种盘吸孔曲线方程,确定了推种装置结构曲线参数方程。选取投种位置和作业速度为主要因素进行全因素试验,对试验结果进行显著性分析,确定了因素与指标的回归方程,以排种粒距合格率、漏播率以及排种粒距变异系数为寻优条件,确定较优的投种位置为直线推种区角度=15°,直线落种角度=21°,并进行验证试验。试验结果表明,作业速度12 km/h时,排种粒距合格率为98.68%,漏播率为0.69%,排种粒距变异系数为15.03%,与理论优化结果基本一致。进行了直线投种方式与原有阻气投种方式的对比试验,结果表明,各个作业速度下排种器性能指标均有所提升,且提升幅度随着作业速度的提高而增大,在作业速度14 km/h时,直线投种较原有阻气投种排种粒距合格率提高4.22个百分点,漏播率降低4.20个百分点,排种粒距变异系数降低4.55个百分点,采用直线投种方式可大大改善播种效果,提高作业速度。     

Relationships between dairy powder surface composition and wetting properties during storage: importance of residual lipids

The relationships between powder surface composition and powder rehydration properties under variable conditions of storage are investigated in this paper. A rheological approach was used to evaluate the modifications induced by storage on the rehydration properties of native phosphocaseinate powder. Concurrently, the powder surface composition (i.e., lactose, proteins, and lipids) was evaluated by X-ray photoelectron spectroscopy (XPS). A strong correlation was found between the powder wetting time lengthening and the migration of lipids on the powder surface during storage. XPS studies indicated also an over-representation of lipids on the powder surface (6%) in comparison with total lipids (0.4%) even on fresh powder before storage. Detailed investigation of powder lipids revealed the presence of high levels of polar lipids (66% compared with <1% in milk lipids). Their amphiphilic nature and their melting points could explain the extensive enrichment of lipids observed at the powder surface during processing and storage.     

The maize primary cell wall microfibril: a new model derived from direct visualization

Understanding the molecular architecture of the plant cell wall is critical to reducing the biomass recalcitrance problem, which currently impedes economic bioconversion processing. The parenchyma cell walls from field senesced, maize stem pith have been directly visualized without extraction processes using high-resolution atomic force microscopy (AFM). By imaging the cell wall inner surfaces from different cells and different faces of the same cell, we were able to map the native primary cell wall ultrastructures. Depending on the thickness of non-cellulosic deposition, the parallel-microfibrils appear in various morphologies ranging from clearly defined to completely embedded in the wall matrixes forming cell wall lamella. Macrofibrils were found to exist only on the uppermost layer of the native primary cell wall and appeared to be bundles of elementary fibrils. This novel observation led us to a new hypothesis for the cell wall fibrillar network and biosynthesis processes. Put concisely, a number of elementary fibrils are synthesized at one locus, that of the cellulose synthase complex (CelS), and coalesce into much larger macrofibrils. These macrofibrils eventually split at the ends to form parallel microfibrils with deposition of other cell wall components (i.e. hemicelluloses, pectin, etc.) also evident. On the basis of these AFM surface measurements and current supportive evidence from cell wall biophysics, biosynthesis, and genomics, we propose a new molecular model consisting of a 36-glucan-chain elementary fibril, in which the 36-glucan chains form both crystalline and subcrystalline structures. We also propose a modified model of CelS based on recently reported experimental evidence from plant cell wall biosynthesis.     

Fibril assemblies in aqueous whey protein mixtures

Fibril formation in mixtures of whey proteins upon heating at pH 2 was investigated. Fibrils were found to coexist with other structures, such as spherulites. These spherulites consist of radially oriented fibrils. At total protein concentrations above 6 wt %, transparent gels were formed. Changing the ratio between the various whey proteins did not affect this gelation concentration as long as beta-lactoglobulin (beta-lg) was present, suggesting that beta-lg was dominant in the gelation. Pure alpha-lactalbumin and pure bovine serum albumin did not form fibrils, nor did they gel upon heating at pH 2 and 80 degrees C for up to 10 h. They did however induce a decrease in the beta-lg concentration needed for gel formation upon heating at pH 2. Our results suggest that beta-lg is the only fibril forming protein at the conditions used and that no mixed fibrils are formed.     

垄沟集雨覆盖对旱作马铃薯块茎淀粉颗粒形态、颗粒分布及糊化特性的影响

为探讨垄沟集雨覆盖栽培对旱作马铃薯块茎形成过程中淀粉颗粒形态、颗粒分布及糊化特性的影响,以马铃薯栽培品种青薯9号为材料,设置全膜双垄(M2)和地膜垄作(M1)覆盖栽培模式,以露地平播为对照(MO),采用扫描电镜、激光粒度仪、粘度分析仪,测定马铃薯块茎形成过程中淀粉的颗粒形态、分布及糊化特性指标.结果表明,从块茎发育全程...     

热泵-热风组合干燥方式对干制海参品质的改善

为了提高干制海参的品质,该文在热风干燥的基础上,利用热泵－热风组合干燥的方式干燥腌渍海参,对不同干燥方式下海参的干燥特性（干燥特性曲线,收缩系数和产品品质）进行测定,对干燥结束后海参的复水品质（复水倍数,流变学参数,感官评价）与传统的热风干燥进行分析比较,结果表明：组合干燥海参的平均收缩系数最小,为16.64,而平均复水倍数为10.18,远高于热风干燥产品;产品流变学特性及硬度,弹性,柔韧度,黏性均较热风处理后海参理想。结果表明：组合干燥可以明显提高干燥后海参的复水倍数和复水品质,产品的感官品质好。     

Measuring Oxidative Gelation of Aqueous Flour Suspensions Using the Rapid Visco Analyzer

The Rapid Visco Analyzer (RVA) was investigated as a tool to measure oxidative gelation capacity (OGC) of aqueous wheat flour suspensions. One club wheat patent flour was used to determine optimal hydration time, and 33 straight‐grade flours (representing 12 hard and 21 soft varieties) were used to observe varietal differences in OGC. A 33.3% w/w flour–water suspension was tested in the RVA at 30°C and 160 rpm for 1 min to establish the flour–water baseline viscosity, and then 65 μL of 3% H₂O₂ was added and the viscosity of the suspension measured at 160 rpm for a further 5 min. Flour from the club wheat showed that 20 min of prehydration was needed to observe full OGC potential. For the 33 straight‐grade flours, final RVA water baseline viscosity was correlated with Bostwick Consistometer (BC) flow (r = −0.93, P ≤ 0.01), and RVA H₂O₂ peak viscosity was correlated with H₂O₂ BC flow (r = –0.81, P ≤ 0.01). The RVA was able to differentiate H₂O₂‐reactive from nonreactive flours. The RVA can observe phenomena not observable with the BC method (e.g., viscosity reduction over time at constant shear rate), which can provide potentially valuable additional information about the nature of OGC in wheat flour suspensions.     

Mechanism of Interactions between Calcium and Viscous Polysaccharide from the Seeds of Plantago asiatica L

The present study aimed at investigating the mechanism of interactions between calcium and the psyllium polysaccharide. Plantago asiatica L. crude polysaccharide (PLCP) was subjected to ethylenediaminetetraacetic acid (EDTA) to yield calcium-depleted polysaccharide named PLCP-E. There was essentially no difference in the structure between PLCP-E and PLCP. However, PLCP-E exhibited a much lower apparent viscosity compared to that of PLCP. PLCP was treated with sodium hydroxide to deplete ferulic acid. The resultant material was named PLCP-FAS, which also exhibited lower viscosity. Adding Ca(2+) could both increase apparent viscosity of PLCP-E and PLCP-FAS, but only PLCP-E could keep the high viscosity when dialysis was carried out to remove free Ca(2+) in the solution. Thermal analysis showed that the thermal stability of the polysaccharide was reduced after EDTA chelation. Scanning electron microscopy (SEM) analysis showed that PLCP-E was flaky and curly aggregation, while PLCP was mostly filamentous in appearance. The results suggested that there are strong interactions between Ca(2+) and the polysaccharide. The interactions contributed to the high viscosity, weak gelling property, and thermal stability of the polysaccharide.     

Growth kinetics of amyloid-like fibrils derived from individual subunits of soy β-conglycinin

The amyloid-like fibrillation of soy β-conglycinin subunits (α, α', and β) upon heating (0-20 h) at 85 °C and pH 2.0 was characterized using dynamic light scattering, circular dichroism (CD), binding to amyloid dyes (Thioflavin T and Congo red), and atomic force microscopy. The fibrillation of all three subunits was accompanied by progressive polypeptide hydrolysis. The hydrolysis behaviors, fibrillation kinetics, and morphologies of amyloid-like fibrils considerably varied among α, α', and β subunits. Faster hydrolysis rates and special fragments were observed for the α and α' subunits compared to the β subunit. However, the order of the fibrillation rate and capacity to form β-sheets was α' > β > α, as evidenced by CD and Thioflavin T data. Moreover, sequential growth of twisted screw-structure fibrils, leading to macroscopic fibrils with distinct morphological characteristics, was observed for β-conglycinin and individual subunits. The different fibrillation kinetics and morphologies of α, α', and β subunits appear to be associated with the differences in the amino acid composition and typical sequence of peptides. Besides, the disruption of ordered structure of fibrils occurred upon further heating (6-20 h) due to extensive hydrolysis. These results would suggest that all subunits are involved in the fibrillation of β-conglycinin, following multiple steps including polypeptide hydrolysis, assembly to amyloid structure, and growth into macroscopic fibrils with a fibril shaving process.     

Collagen fibril alignment and deformation during tensile strain of leather: a small-angle X-ray scattering study

The distribution and effect of applied strain on the collagen fibrils that make up leather may have an important bearing on the ultimate strength and other physical properties of the material. While sections of ovine and bovine leather were being subjected to tensile strain up to rupture, synchrotron-based small-angle X-ray scattering (SAXS) spectra were recorded edge-on to the leather at points from the corium to the grain. Measurements of both fibril orientation and collagen d spacing showed that, initially, the fibers reorient under strain, becoming more aligned. As the strain increases (5-10% strain), further fibril reorientation diminishes until, at 37% strain, the d spacing increases by up to 0.56%, indicating that significant tensile forces are being transmitted to individual fibrils. These changes, however, are not uniform through the cross-section of leather and differ between leathers of different strengths. The stresses are taken up more evenly through the leather cross-section in stronger leathers in comparison to weaker leathers, where stresses tended to be concentrated during strain. These observations contribute to our understanding of the internal strains and structural changes that take place in leather under stress.     

免耕播种机播种质量红外监测系统设计与试验

为了对播种机播种质量进行监测,实现精量播种,该文采用红外检测技术,设计了一种对射式传感器,研制了配套播种质量监测系统,并进行了田间播种作业试验研究。该监测系统由多路传感器、监控终端、播种传动传感器组成,结构合理,安装方便,对播种过程出现的堵塞、漏播、缺种等现象,可发出声光报警信号,及时指示故障的位置。田间试验中监测数据与实际测量对比结果表明:该监测系统能够适应田间工作环境,播种质量监测准确率可达95%以上,能够解决人工难以实时监测播种质量的问题,可避免漏播断条现象发生,提高播种机的工作效率和播种质量。     

Nitrogen,Phosphorus, and Potassium Availability in Manure- and Sewage Sludge–Applied Soil

A field experiment with wheat (Triticum aestivum L.) was established over two growing seasons where farmyard manure and sewage sludge, along with conventional fertilizer, were added to soil. We found that ammonium N was at greater concentrations in the organic amendments treatments, indicating more beneficial dynamics (i.e., it can be taken up by plants for a greater amount of time) and thus a longer lasting effect as a nutrient for the test crop. We found that nitrogen (N), phosphorus (P), and potassium (K) uptake increased with added organic amendments. This means that when organic matter along with nutrients are added to soil, productivity may increase beyond preset targets because soil conditions greatly improve, not only chemically but also physically. Nitrates left over at the end of the growing season (residual N) were greater in the high sewage sludge and manure treatments, but not proportionally.     

Synthesis and characterization of zinc-coated urea fertilizer

The research was focused on the synthesis and characterization of zinc (Zn)-coated urea fertilizer. Zinc oxide (ZnO) particles were coated on urea granules through two different coating techniques, i.e., slurry coating and wet coating, and the release rate of the coated Zn was measured up to 24 hours. Slurry coating technique showed better Zn release rate and morphology of coated urea granules as compared with wet coating technique using different binders, i.e., water, molasses, paraffin oil, and the combined mixture of honey bee wax and gum arabica. Urea granules synthesized through wet coating technique have a low amount of Zn as compared with slurry-coated urea granules. Urea granules coated through slurry coating technique and molasses, paraffin oil, and water (MPW) as a binder were the best in term of coating efficiency, uniform size distribution of ZnO-coated particles, granule's morphology, and release rate of Zn from coated formulations.