醋酸乙烯酯类固沙剂固沙效果的风洞实验

通过室内风洞模拟实验,研究了不同净风、挟沙风风速和沙面坡度条件下3种醋酸乙烯酯类固沙剂(WGS-3、WGS-4和CS-204)不同喷洒浓度时的土壤风蚀控制效果。研究结果表明:3种固沙剂均具有较好的抗风蚀能力,相同条件下,固沙剂CS-204的抗风蚀性能稍强于WGS-4,WGS-3的抗风蚀性能相对较差;与净风相比,挟沙风更易使喷施固沙剂后的沙面产生风蚀;挟沙风条件下,沙面累积风蚀量随固沙剂使用量的增加而减小,随沙面坡度的增加而增大;从经济意义上考虑,建议固沙剂WGS-3喷洒浓度稍高于3.0%,WGS-4和CS-204使用浓度为2.0%~3.0%,且喷洒量为1L/m2,能有效固沙。     

Structural Characteristics,Properties, and In Vitro Digestibility of Rice

Using rice samples derived from normal rice cultivars and endosperm starch mutant, we investigated key factors contributing to the enzyme digestibility of steamed rice grains. The chemical composition of polished rice grains, structural features of endosperm starch, and enzyme digestibility of steamed rice grains were examined. The protein content of polished rice grains was 4.6–9.1%, amylose content was 4–27%, the DP_n of purified amylose was 900–1,600, the amylopectin short/long chain ratio was 1.2–5.9, and the enzyme digestibilities of steamed polished rice grains were 0.9–12.6 °Brix. Amylose content and RVA parameters (viscosity, breakdown, and setback) correlated significantly with enzyme digestibility of steamed rice grains. Multiple regression formulas were constructed to predict digestibility of steamed rice grain as a function of the molecular characteristics of the starch. When both amylose content and the short/long chain amylopectin ratio were used as predictor variables, they accounted for >80% of the observed variance in digestibility of steamed rice grains. Multiple regression revealed that the more digestible rice samples had starch with a lower amylose content and more short‐chain amylopectin. Reassociation of amylose‐lipid complex and recrystallization of amylopectin in the stored steamed rice grains was monitored by differential scanning calorimetry (DSC), and the observed retrogradation properties were related to the structural characteristics of starch and to the enzyme digestibility of steamed rice grains.     

Selected Functional Properties of Extruded Starch Acetate and Natural Fibers Foams

Response surface methodology was employed to study the functional properties of starch acetate foams blended with 0, 7.5, and 15% wood, oat, and cellulose fibers. The blends were extruded with 14, 17, and 20% ethanol as a blowing agent, using a twin‐screw extruder with 160°C barrel temperature and 225 rpm screw speed. Physical characteristics of the extrudates including radial expansion ratio, unit density, and bulk density; and mechanical properties including unit spring index and bulk spring index were determined. Scanning electron micrographs were taken to observe foam cell textures. Higher fiber content resulted in lower radial expansion. Ethanol content had a positive effect on foam expansion. Higher expansion was obtained in starch acetate‐cellulose foams because better starch acetate‐fiber matrix was formed. Mechanical properties increased with higher fiber and ethanol contents. Micrographs showed that uniform cell structures were associated with better mechanical properties.     

Morphological,Structural, and Thermal Properties of Starch Nanocrystals Affected by Different Botanic Origins

Six types of starch nanocrystals were prepared from corn, barley, potato, tapioca, chickpea, and mungbean starches with an acid hydrolysis method. The yields and morphological, structural, and thermal properties of starch nanocrystals were characterized. Starch nanocrystals had yields ranging from 8.8 to 35.7%, depending on botanical origin. During acid hydrolysis, amylose was effectively degraded, and no amylose was detected in any starch nanocrystal. Shape and size of native starch granules varied between starches, whereas there was no obvious difference in shape among different types of starch nanocrystals. The average particle size of starch nanocrystals was mainly related to crystalline type of native starches. Compared with their native starch counterparts, changes in crystalline diffraction patterns of starch nanocrystals depended on the original botanical source and crystalline structure. Degree of crystallinity, melting temperature, and enthalpy of starch nanocrystals increased, whereas their thermal decomposition temperature decreased. Of six produced starch nanocrystals, potato starch nanocrystal had the lowest yield, degree of crystallinity, and onset and melting temperatures, the largest particle size, and obvious changes in crystalline diffraction pattern.     

猕猴桃低乙烯气调库的性能和贮藏效果

介绍了猕猴桃低乙烯气调库。测定了库体的性能,研究了贮藏方式对猕猴桃贮藏性状的影响。结果表明：库体密封性能达良好级,乙烯浓度脱至０．０２μＬ／Ｌ以下;低乙烯气调可延缓果实后熟软化。在两年１８００００ｋｇ果实商业贮藏中,果实贮期可达１８０天以上,果肉硬度为６．８ｋｇ／ｃｍ^２,好果率大于９８％,货架期大于１５天。低乙烯气调是猕猴桃的最佳贮藏方式     

Air and Moisture Transport Properties of Low‐Oil DDGS

Distillers dried grains with solubles (DDGS) are widely used as feed for cattle, dairy, and swine because of their protein, fiber, amino acids, fat, and other vital nutrients. Corn ethanol plants in the United States recently have started extracting oil from DDGS to gain additional profit, thus producing low‐oil DDGS. So far, there has been no comprehensive study reported with bulk handling and flowability properties of low‐oil DDGS. We measured the air resistance, moisture diffusivity, and air permeability properties for low‐oil DDGS at different temperature and relative humidity conditions, along with some important physical and chemical properties. Physical property comparisons between regular and low‐oil DDGS showed differences in key properties such as particle size, color, density, porosity, and angle of repose. The modified Henderson model predicted the equilibrium moisture content (EMC)–equilibrium relative humidity (ERH) relationship of low‐oil DDGS with a low standard error of regression value (0.008); it showed no pattern in the residuals and was judged the most appropriate model tested for EMC‐ERH predictions. Results of EMC‐ERH nonlinear modeling were used to define conditions for moisture diffusivity. Moisture diffusivities of low‐oil DDGS at varying drying temperatures ranged from 0.74 × 10⁻¹¹ to 1.77 ×10⁻¹¹m²/s. The properties are important for understanding and modeling heat and moisture transport through and flow properties of low‐oil DDGS.     

Evaluation of Textural and Structural Properties of Barbari Bread During Storage

This study was performed using three Barbari flours (strong, medium, and weak) with different physical, chemical, and rheological properties. Determination of texture firmness of Barbari breads (A, B, and C, made of strong, medium, and weak flours, respectively) during storage was carried out with a texture analyzer and evaluating the bread crumb properties and changes during storage with a nondestructive ultrasonic technique. The bread microstructure was assessed with scanning electron microscopy, and the general process of starch gelatinization and retrogradation was evaluated with differential scanning calorimetry. The bread sensory properties were evaluated by 10 trained panelists. Barbari A, made from strong flour, had less firmness, lower transition of ultrasonic wave velocity, lower value of elastic modulus, reduced value of enthalpy, lower average temperature, larger pore diameter and area of images, and higher point total in sensory evaluation than Barbari B and Barbari C, particularly the latter, as storage time progressed. Barbari A's desirable quality characterization and longer shelf life were owing to the qualities of the flour, which enabled the production of dough with the appropriate properties. Eventually, the results of device‐based and sensory tests were significantly correlated. Ultrasonic nondestructive testing is recommended over other methods for assessing the texture, cell structure, and elastic properties of bread after baking and during storage, because it is fast, nondestructive, and less expensive than other methods and can be used during production.     

Black Sesame Pigment: DPPH Assay-Guided Purification, Antioxidant/Antinitrosating Properties, and Identification of a Degradative Structural Marker

An improved purification procedure leading to black sesame ( Sesamum Indicum L.) pigment was developed involving fat removal by treatment of ground black sesame seeds with dichloromethane followed by an optimized hydrolytic protocol with 6 M HCl, at 100 °C, overnight. The black pigment thus obtained displayed good antioxidant efficiency by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay (82% reduction at 0.5 mg/mL), good ferric ion-reducing capacity (61 μM Trolox equivalent concentration at 0.5 mg/mL), and potent antinitrosating properties (74% inhibition of 2,3-diaminonaphthalene (DAN) nitrosation at gastric pH at 2.5 mg/mL). A synthetic pigment obtained by oxidative polymerization of coniferyl alcohol (polyconiferyl alcohol, PCA), the putative biosynthetic precursor to the sesame pigment, was characterized as a reference standard. FT IR spectra of the purified sesame pigment and PCA supported the structural similarity. HPLC analysis of degradation products by alkaline hydrogen peroxide of purified black sesame pigment showed the formation of vanillic acid (VA) as the main isolable fragment. Similar yields of VA were obtained by degradation of PCA. A positive correlation between VA yields and DPPH activity was determined in samples of different purities. It is suggested that VA is a structural marker of black sesame pigment, confirming the biosynthetic origin from coniferyl alcohol and pointing to the o-methoxyphenol motif as the key factor accounting for the potent antioxidant properties of the pigment.     

Physical Properties of Poly(Lactic Acid) and Starch Composites with Various Blending Ratios

Two‐phase polymer blends of poly(lactic acid) (PLA) and corn or wheat starches at various ratios were prepared by using a laboratory‐scale twin‐screw extruder and compression molding. The blends were characterized for thermal transitions, mechanical properties, and water absorption. Starch and PLA were immiscible polymers, and the thermal behavior of PLA was not affected by starch. Crystallinity of the blends decreased in some degree as starch content increased 20–40%. Tensile strength and elongation of the blends decreased as starch content increased, but modulus increased as starch content increased up to 70%. As starch content increased to >60%, the PLA phase became discontinuous, and water absorption of the blends increased sharply. Blends made from wheat starch gave slightly better mechanical properties than those made from corn starch, and no differences in other properties were observed.     

黄原胶-N-乙烯基吡咯烷酮辐射接枝共聚物的制备及结构特性研究

为提高黄原胶分子的应用性能,以60Co-γ为辐射源,对黄原胶和N-乙烯基吡咯烷酮进行共辐射接枝处理,制备黄原胶-N-乙烯基吡咯烷酮共聚物(XG-g-NVP),并研究反应条件对接枝率和单体利用率的影响及共聚物的结构表征。结果表明,当辐射吸收剂量为10k Gy,黄原胶浓度12g·L-1,NVP/XG质量比8∶1,4-甲氧基酚阻聚剂添加量为NVP单体质量的0.01%时,最佳接枝率为543.3%,单体利用率为67.9%。红外光谱表明接枝反应发生在NVP乙烯基部位,扫描电镜图显示共聚物形貌由片层状逐步过渡到颗粒状;XG-g-NVP的抗高温及抗剪切能力相比黄原胶有所提高,且黏度值在高温、高剪切力时仍保持恒定值,因此,改性后的黄原胶结构及热稳定性提高。通过对黄原胶分子接枝改性,使其具备了更多优良的性能,为改性黄原胶的进一步应用奠定了理论基础。     

Proteins Extracted from Defatted Wheat Germ: Nutritional and Structural Properties

The main by‐product of the wheat germ oil extraction process is a defatted wheat germ meal, which has a relatively high protein content, making it an attractive and promising source of vegetable proteins. Four protein fractions (albumin, globulin, prolamine, and glutelin) and protein isolate from defatted wheat germ flour (DWGF) were fractionated and then characterized by amino acid analysis, SDS‐PAGE, and differential scanning calorimetry (DSC). Albumin was the major fraction (34.5%) extracted, followed by globulin (15.6%), glutelin (10.6%), and prolamine (4.6%). Protein isolate was mainly composed of albumin and globulin. These protein fractions and protein isolate showed an excellent balance of all essential amino acids, with a relatively high level of glutamic acid, arginine, leucine, and glycine, whereas cystine was lacking. All the estimated nutritional quality parameters based on amino acids composition showed that defatted wheat germ proteins had good nutritional quality. Nonreduced and reduced SDS‐PAGE analyses showed that S‐S bonds ere deficient in the structure of wheat germ proteins. The albumin fraction consisted of 19 major polypeptide bands with M_r 14,000–84,000. The globulin fraction showed four distinct polypeptides or polypeptide group bands with M_r 55,000, 37,000–43,000, 24,000, and 12,000–20,000, which may be the components of the 8S‐type and 11S‐like proteins. The prolamine fraction showed a predominant doublet‐like band at M_r 17,000–16,000, while the glutelin fraction showed five major polypeptide bands with M_r 39,000, 20,000, 18,000, 17,000, and 14,000. Protein isolate and DWGF showed very similar SDS‐PAGE patterns. Except for prolamine and glutelin fractions without detectable calorimetric response, the globulin fraction possessed the highest thermal stability (T_d = 83.80°C, ΔH =1.36 J/g ), followed by protein isolate (T_d = 80.05°C, ΔH = 0.76 J/g), while the albumin fraction was lowest (T_d = 69.72°C, ΔH = 0.53 J/g). The findings on defatted wheat germ proteins are important for their potential application as functional food ingredients.     

黄土高原土壤物理性质对养分迁移速率的影响

采用一维饱和稳定流易混置换试验,用Cl-和K 为对象模拟黄土高原地区4种典型土壤对养分运移阻滞因子R的影响。试验结果表明对于不同质地的土壤,随着土壤质地变细,运移阻滞因子增大;对于同种质地土壤,随着容重增加,运移阻滞因子增大;对于同种质地而粒级不同的土壤,运移阻滞因子随着粒级的增大而增大;受土壤排斥的离子较受土壤吸引的离子容易穿透土壤。     

Influence of Vacuum Mixing on Structural Characteristics and Physical Properties of Noodle Dough

The effects of vacuum mixing on the structural characteristics and physical properties of noodle dough were investigated using three leading Chinese wheat cultivars. Texture profile analysis showed that vacuum mixed doughs when sheeted all gave significantly higher levels of adhesiveness, elasticity, and chewiness than doughs from nonvacuum mixing. The cross section of sheeted dough mixed at 0.06 MPa had a more continuous and compact microstructure with fewer holes and gaps, as well as more even protein distribution at the surface, as evidenced by scanning electron microscopy and Fourier transform infrared microimaging. However, a higher degree of vacuum was detrimental to the developed network for weak dough. Dough mixed at 0.06 MPa had higher glutenin macropolymer content and lower free thiol group concentration compared with nonvacuum mixed doughs, which may largely relate to the improvement of dough texture. The development of the gluten network for weak gluten flour was more sensitive to the degree of vacuum.     

Biodegradation of Monoethanolamine,Ethylene Glycol and Triethylene Glycol in Laboratory Bioreactors

The release of alkanolamines and glycols into the subsurface soils poses a potential hazard to the environment through impacted soil and groundwater. This study investigated aerobic and anaerobic biodegradability of monoethanolamine (MEA), ethylene glycol (MEG) and triethylene glycol (TEG). Significant levels of MEA (31 000 mg/kg), MEG (500 mg/kg) and TEG (2100 mg/kg) were successfully aerobically biodegraded in bioreactors. The aerobic slurry experiments suggested initial phosphate (P) limitation, as biodegradation rates increased by one order of magnitude after phosphate addition. Anaerobic decay of MEA, MEG and TEG was unaffected by P-addition. MEA, MEG and TEG degradation products such as acetate, ethanol and ammonium at about 75 000 mg/kg, 8100 mg/kg and 8800 mg/kg degraded completely and did not prevent aerobic biodegradation. This study confirms proposed biodegradation pathways of MEA, MEG, TEG and their breakdown products in natural soil and groundwater using indigenous microbes. Levels of contamination studied here are significantly higher than previously reported.     

Effect of β‐Glucan on Technological,Sensory, and Structural Properties of Durum Wheat Pasta

β‐Glucan is known to have valuable properties for preventative health and is finding widespread use in foods. This study investigated the benefit of adding a commercial source of β‐glucan, Barley Balance (BB) flour, as a functional ingredient in spaghetti. Durum wheat semolina was substituted with BB at levels of 7.5, 15, and 20%, from which spaghetti was prepared on a laboratory scale. The substitution of BB increased the β‐glucan content of semolina from 0.3 to 6% in uncooked and 8% in cooked pasta. Antioxidant activity (measured by 2,2‐diphenyl‐1‐picrylhydrazyl) increased with BB and did not decline significantly on processing and cooking. Compared with the control, 7.5% BB had no or minimal effect on pasta cooking loss, stickiness, water absorption, aroma, and sensory texture. However, at higher doses, pasta became less yellow and more brown, firmer, of inferior aroma, more rubbery, and chewy, but less floury to the mouth. The extent of starch digestion decreased with increasing quantities of BB, suggesting that BB may lower glycemic index, with microscopy data suggesting that this decrease was mediated through the development of a more intensive fiber or fiber/protein matrix retarding enzymatic access to starch granules.     

几种胡敏酸和富里酸分子结构模型的三维可视化与特性研究

针对已提出的几种胡敏酸和富里酸的二维分子结构模型,应用HyperChem软件转换为三维结构并进行几何优化,计算了这些三维模型的能量以及定量构效关系(QSAR)参数。结果表明:几种模型在三维结构和特性上都各不相同,这为从空间角度更直观地认识腐殖物质的分子结构提供了可能性。     

植物吸收转运硝态氮及其信号调控研究进展

硝态氮是植物吸收利用的主要氮源,其吸收利用是一个高度协调复杂的调控过程。植物为了在各种变化的环境中生存,进化出了适宜不同环境的硝态氮吸收利用机制。植物根系中存在不同类型的硝态氮受体,可以感受外界硝态氮浓度变化,并启用高亲和力或低亲和力硝态氮吸收系统,从而吸收硝态氮;硝态氮进入根系后,大部分被运输到地上部进行同化作用,合成大分子物质,以促进植物生长;如果地上部硝态氮含量过多,植物可把多余的硝态氮运送到液泡内储存,待需要时再从液泡转运至细胞质中利用。植物生长发育过程中,老叶和成熟叶片中的硝态氮可被转运到新生组织中,促进新生组织生长。硝态氮吸收利用过程中大量硝态氮吸收、转运、储存、同化和信号调控基因被有序激活并协调工作,促进植物高效吸收利用硝态氮。本文主要针对NRT1和NRT2硝态氮吸收转运相关基因及其功能,以及参与初级硝态氮反应的相关转录因子和小信号多肽在硝态氮信号传导和组织间的信号交流进行综述,以便深入理解植物吸收利用硝态氮的机理,为高效利用氮素的作物育种和栽培技术的创建提供新的思路。     

Effect of Oil Content and pH on the Physicochemical Properties of Corn Starch‐Soybean Oil Composites

Starch‐lipid composites are a new category of fat replacers. The physicochemical properties of reconstituted corn starch and soybean oil composites (CSSBOC) were evaluated and compared with the properties of reconstituted jet‐cooked corn starch (JCCS). Gel firmness, thermal properties, and hot pasting properties at two pH levels and two oil content levels were studied. Amylose content of CSSBOC was unaffected by processing. Buffer pH significantly affected the firmness of the gels made with JCCS. Gels appeared to have a more ordered structure and were firmer at pH 3.4 than at pH 6.0. The firmness of gels made with CSSBOC was not affected by pH or oil content. Retrogradation enthalpy of the gels made with JCCS was significantly affected by pH. Differences in the thermal characteristics of gels made with CSSBOC were attributed to pH and oil content. Peak viscosity, cold paste viscosity, and breakdown viscosity changed significantly when CSSBOC pastes were reconstituted in different pH buffers. Only hot paste viscosity and cold paste viscosity changed significantly when JCCS pastes were reconstituted in different pH buffers. Results establish critical parameters for processing decisions and for the understanding of the behavior of CSSBOC in food system models in which pH is an important factor.     

Ethylene oxidation,atmospheric methane consumption,and ammonium oxidation in temperate volcanic forest soils

Temperate volcanic forest surface soils under different forest stands (e.g., Pinus sylvestris L., Cryptomeria japonica, and Quercus serrata) were sampled to study the kinetics of ethylene (C₂H₄) oxidation and the C₂H₄ concentrations that effectively inhibit oxidation of atmospheric methane (CH₄) and nitrification. The kinetics of C₂H₄ oxidation in temperate volcanic forest soils was biphasic, indicating that at least two different microbial populations, one with low and another with high apparent K _m values, were responsible for ethylene oxidation. Methane consumption activity and ammonium oxidation of soil were inhibited by adding ethylene. Added C₂H₄ at concentrations of 3, 10, and 20 μl C₂H₄ per liter in the headspace gas respectively reduced by 20%, 50%, and 100% atmospheric CH₄ consumption by soil, and these values were much smaller than those inhibiting ammonium oxidation in these forest soils; thus, the CH₄ consumption activity was more sensitive to the addition of C₂H₄ than ammonium oxidation. Previous studies have shown that accumulation of C₂H₄ in such volcanic forest soils within 3 days of aerobic and anaerobic incubations can reach a range from 0.2 to 0.3 and from 1.0 to 3.0 μl C₂H₄ per liter in the headspace gas, respectively. It is suggested that C₂H₄ production beneath forest floors, particularly after heavy rain, can to some extent affect the capacity of forest surface soils to consume atmospheric CH₄, but probably, it has no impact on ammonium oxidation.