Water Vapor Barrier Properties of Zein Films Plasticized with Oleic Acid

Water sorption, water vapor permeability, and tensile properties were evaluated for zein films plasticized with oleic acid. The effect of relative humidity on water vapor permeability and tensile properties of films was investigated. Samples were produced by two different methods: casting from a zein solution and stretching from a zein-fatty acid resin. Films were also coated with linseed oil. Results indicated that preparation method affected water sorption and permeability of zein films. Resin films showed lower water sorption than cast films, especially at high A_w values. Water vapor permeability was also lower for resin films. Coating with linseed oil further improved water vapor barrier ability of resin films. Permeability was affected by environmental relative humidity; higher relative humidity resulted in increased permeability. Environmental relative humidity also affected tensile properties of resin films. Toughness and elongation were improved when relative humidity increased from 50 to 85% rh. Tensile strength showed a maximum at 75% rh. Coating improved elongation and toughness of films. Maximum elongation and toughness were observed for coated samples at 85% rh. Zein resin films showed good tensile and water barrier properties that were maintained through environmental humidity levels from 50 to 98% rh.     

Properties and Microstructure of Plasticized Zein Films

A new method for preparation of zein films involving plasticization of zein with oleic acid to form an intermediate moldable resin was presented. The resin was stretched over rigid frames to form thin membranes that were set in flexible films. The objective of the study was to investigate the effect of film preparation method on film properties. Tensile properties, microstructure, and thermal behavior of zein films plasticized with oleic acid were investigated for films prepared by conventional casting from ethanol solutions and by stretching of plasticized resins. Cast films were stiff and brittle, whereas resin films showed more flexibility and toughness. Differential scanning calorimetry thermograms of cast films indicated phase separations were generated when heated that were not observed for resin films. Microstructure images showed a higher degree of structure development and orientation in resin than in cast films. Glass-transition temperatures of resin films were measured at -94 and 104.4° C, indicating the film remained flexible through a wide temperature range. Resin film flexibility and toughness were attributed to effective plasticization that led to fiber formation and orientation.     

Impact of Thiocyanate Salts on Physical,Thermal, and Rheological Properties of Zein Films

A new class of zein additives was investigated, thiocyanate salts. Ammonium, potassium, guanidine (GTC), and magnesium thiocyanate salts were added to solutions of zein in with various amounts of tri(ethylene glycol) (TEG), cast as films, and then tested to determine the impact that each salt had on properties. The presence of these salts affected solution rheology and intrinsic viscosity, demonstrating that the salts interacted with the protein. It was found that these salts acted as plasticizers, as they lowered the glass transition temperature of zein when evaluated with differential scanning calorimetry. In zein films in which TEG was present, these salts increased elongation and reduced tensile strength. However, unlike traditional plasticizers (such as TEG), when the salts were used as the only additive, elongation was not increased and tensile strength was not decreased. Of the salts tested, GTC in combination with TEG was found to increase elongation the most. The impact of salts on elongation was greatly affected by the relative humidity in which the samples were stored.     

Effect of Hydrophilic Plasticizers on Thermomechanical Properties of Corn Gluten Meal

The glass transition temperature and rheological moduli of plasticized corn gluten meal (CGM) were determined with dynamic mechanical thermal analysis (DMTA). The tested plasticizers were water, glycerol, polyethylene glycols (PEG) 300 and 600, glucose, urea, diethanolamine, and triethanolamine, at concentrations of 10–30% (dwb). The glass transition temperature (T_g) of CGM, measured at 188°C when unplasticized, was lowered by >100°C at 30% plasticizer content, except by PEG 600 and glucose, which showed limited compatibility with CGM proteins. The highest plasticizing efficiency, on a molar basis, was measured with PEG 300 and was attributed to the large number of hydrophilic groups and the high miscibility of this compound with CGM proteins. The change in T_g due to the plasticizing effect was modeled with the Gordon and Taylor equation, but a better fit of the experimental data was obtained with the Kwei equation.     

Corn Gluten Meal as a Thermoplastic Resin: Effect of Plasticizers and Water Content

Corn gluten meal (CGM) was studied to investigate the effect plasticizers and water have on its melt processing, and how this melting affects its mechanical properties. GCM containing varying amounts of water were mixed with 23% (w/w) plasticizers; (glycerol, triethylene glycol (TEG), dibutyl tartrate, and octanoic acid in a Haake bowl mixer at 80°C. The amount of water in the CGM affected the amount of torque produced in the Haake mixer. This increase in torque was correlated with how well the CGM melted in the mixer. SEM images of CGM melted in the mixer showed a more uniform homogenous structure when processed at its optimum moisture content. Glycerol, TEG, and dibutyl tartrate produced the greatest torque when the CGM contained <1% water. Octanoic acid produced the greatest torque when the CGM was processed at 8% moisture. CGM plasticized with TEG and octanoic acid were mixed at either their optimum moisture or at 9.6% moisture and then compression molded into tensile bars. The tensile strengths of the bars that were mixed at their optimum moisture content were significantly greater than the bars mixed at 9.6% moisture. The tensile properties of the CGM samples were affected by relative humidity (rh). The tensile strength decreased and elongation increased as relative humidity increased. CGM plasticized with TEG saw a greater changes in its tensile properties due to relative humidity than did octanoic acid plasticized CGM.     

Tensile Properties of Extruded Corn Protein Low‐Density Polyethylene Films

The strength of films extruded from powder blends of corn zein or corn gluten meal (CGM) with low‐density polyethylene was investigated. Tensile strength, percent elongation at break, and elastic modulus of the extruded films were measured. The tensile strength decreased from 13 MPa to ≈10.5 MPa with zein addition, while CGM addition resulted in tensile strength of ≈6 MPa. The higher the level of biological material (CGM or zein) in the films the lower the tensile properties. Films containing CGM exhibited significantly lower tensile properties than those containing zein. Extrusion processing of biological films is a step toward commercial viability.     

氨基酸对明胶膜结构及性能的影响

为了探索氨基酸作为明胶膜增塑剂的潜力,本试验研究了不同氨基酸(脯氨酸、亮氨酸、谷氨酸、丝氨酸和甲硫氨酸)对明胶膜厚度、机械性能、水蒸气透过率、透光率、颜色以及结构等的影响。结果表明,与对照组相比,除了甲硫氨酸外,其余的氨基酸都能增加明胶膜柔韧性;除了脯氨酸外,其余的氨基酸都增加了明胶膜的黄度值,并降低了明胶膜透光率和透明度;而添加脯氨酸的明胶膜的柔韧性最好、具有更好的表观特征,表面光滑紧致,同时具有更高的透明度、透光率和柔韧性。根据傅里叶变换红外光谱和二级结构分析发现,添加脯氨酸、丝氨酸和甲硫氨酸能通过氢键与明胶相互作用,降低明胶的无规则卷曲结构含量,增加β-折叠和β-转角结构含量。综合分析认为,脯氨酸可以作为明胶膜的天然增塑剂。本研究结果为增塑剂在明胶膜中的应用提供了新视角。     

Effect of Broken Corn Levels on Water Absorption and Steepwater Characteristics

Broken corn created by grounding sound corn kernels was added back at levels of 0, 4, 8, 12, or 16%, by weight, to whole kernels of three corresponding hybrids: FR27 × FRMo17 (a soft endosperm corn), FR618 × FR600 (amedium‐hard endosperm corn), and FR618 × LH123 (a hard endosperm corn). The samples had been dried from 28% moisture content to 15% moisture content either by using ambient air at ≈25°C or at 110°C. Samples were steeped for 36 hr at 52°C in 0.15% sulfur dioxide and 0.5% lactic acid steeping solution. The steepwater characteristics, such as water absorption, solids and protein content in the steepwater, and steepwater pH, were measured by periodic sampling and analyzed. Broken corn level has a significant effect on the amount of solids released during steeping and steepwater protein content for all samples. Both steepwater solids and protein content increased linearly as broken corn content increased. Corn drying temperature, kernel hardness, and interactions between drying temperature and kernel hardness has a significant effect on steepwater solids and protein content and steepwater pH in both broken and unbroken corn. Corn dried at low temperature released more soluble solids and protein into the steepwater than corn dried at high temperature. Soft endosperm and medium‐hard endosperm corn released more soluble solids and protein into the steepwater than hard endosperm corn. Soft endosperm corn resulted in a higher steepwater pH than medium‐hard and hard endosperm corn. No significant effect of broken corn content on final moisture content of steeped corn and steepwater pH was observed.     

Water Barrier Properties of Zein‐Oleic Acid Films

Free‐standing films were prepared from zein formulations containing 30, 40, 50, 60, 70, and 80% oleic acid (OA). Zein/OA formulations were also used as coating films for rodent diet bars. Water vapor permeability (WVP) of films and moisture loss rate (MLR) of coated rodent diet bars were measured at 4 and 25°C. Temperature affected the water barrier properties of films and coatings. At 4°C, WVP of films decreased with OA concentration while it increased at 25°C. WVP behavior was attributed to oleic acid phase changes due to temperature. At 4°C, OA is a crystalline solid that limits water diffusion through the films. At 25°C, liquid OA increased the system free volume and allowed for water diffusion. The effect was more pronounced the higher the OA concentration in films. Differential scanning calorimetry (DSC) of zein/OA films showed endothermic peaks at 12–18°C, confirming the melting of OA in that temperature range. MLR of coated rodent diet bars was also affected by temperature and OA concentration in coating formulations. In this case, formulations containing 40, 50, and 60% OA were better moisture barriers than coatings with higher OA content at both 4 and 25°C. Moisture losses were reduced at 4°C due to OA solidification.     

生物炭基肥和水分胁迫对花生产量、耗水和养分吸收的影响

为了探究不同生物炭基肥施用量下水分胁迫对花生栽培的应用潜力,运用自动遮雨棚花生盆栽试验,对不同生物炭基肥施用量(0,750,1 500kg/hm2)和不同水分胁迫程度(常规控水,70%~75%田间持水量;中度水分胁迫,60%~65%田间持水量;重度水分胁迫,50%~55%田间持水量)对花生产量、耗水和其养分吸收特征的影响进行研究。结果表明:施入750,1 500kg/hm2生物炭基肥可提高0—15cm土层土壤铵态氮和速效钾含量、植株地上部分氮钾养分吸收和水分生产率;除重度水分胁迫外,其他两种控水水平均能提高土壤速效钾含量,促进植株营养吸收,进而提高产量;中度水分胁迫下,施入750,1 500kg/hm2生物炭基肥,较无生物炭基肥可显著提高植株地上部分氮钾吸收,增产40.48%和37.71%,提高水分生产率53.8%和9.9%。研究结果可为生物炭基肥在干旱地区花生生产的应用方面提供理论依据。     

Properties and Microstructure of Zein Sheets Plasticized with Palmitic and Stearic Acids

Interest in biodegradable materials for packaging and agricultural uses has grown in recent years. Plant proteins have been proposed as inexpensive, renewable, and abundant feedstock. Corn zein was investigated based on value-added considerations and on the unique thermoplastic and hydrophobic properties of zein. Films prepared from zein are known to be tough and resistant, but also hard and brittle, thus requiring the addition of plasticizers to improve flexibility. The objectives of this research were to study the tensile properties, water absorption, and microstructure of zein sheets plasticized with palmitic and stearic acids. Both palmitic and stearic acids showed similar effects as plasticizers of zein. Tensile strength of zein sheets increased with the addition of low levels of plasticizers. However, beyond a critical point, tensile strength decreased with further addition of fatty acids. Water absorption decreased continuously with increasing fatty acid content. Kinetic parameters indicated fatty acids decreased water absorption by decreasing the saturation level of zein sheets. Coating zein with flax oil decreased the rate of water absorption by sealing off surface pores. Scanning electron micrographs of zein sheets showed the development of layered structures as fatty acid content increased. Zein-fatty acid layers were believed to be responsible for the increased tensile strength of plasticized zein sheets and to have contributed to increased resistance to water absorption.     

微咸水与再生水混灌对土壤特性的影响与灌溉效应评估

为了探讨淡水资源不足地区微咸水的合理利用方式.通过盆栽试验,以清水灌溉为对照,研究不同比例微咸水与再生水混合灌溉对水盐、水溶性离子、滴水穿透时间WDPT、有机质以及酶活性的影响,并利用第二代生物综合响应指数法(IBRv2)对微咸水与再生水混灌效应进行评价.结果 表明:(1)与再生水灌溉(T1)相比,随着混合溶液中微咸水...     

高吸水树脂的性能及其在农业上的应用

综述了新型化学抗旱节水材料?高吸水树脂的种类、吸水原理、主要的性能特征以及具体的使用方法。高吸水树脂可以通过抑制水分蒸发,增加土壤含水量以及改良土壤结构等方面,起到保水和促进作物生长发育以及提高产量的作用。指出了我国应在开发研制高吸水树脂保水剂的种类,提高释水性能和降低价格等方面加强研究。     

乌贼墨黑色素纳米粒对明胶-普鲁兰多糖复合膜的性能影响及表征

为探究乌贼墨黑色素纳米粒(MNP)对明胶-普鲁兰多糖(Gel/Pul)复合膜的改性效果,本研究以乌贼墨为原料,利用动态高压微射流技术制备MNP,以明胶、普鲁兰多糖为成膜基质,添加MNP制备纳米复合膜,通过水蒸气透过率(WVP)、透油率、光学性能、机械性能和自由基清除率等指标,考察了MNP添加量对复合膜的物理特性和抗氧化能力的影响,并通过傅里叶红外光谱(FTIR)和扫描电镜(SEM)进行微观表征,探究MNP与成膜基质间的相互作用。结果表明,MNP与Gel/Pul基质存在氢键的相互作用,具有良好的生物相容性;MNP的加入可以改善纳米复合膜的水蒸气阻隔性和机械性能;当MNP添加量为1 wt%时,复合膜的水蒸气透过率最小,抗拉强度达到最大值;随着MNP添加量的增加,纳米复合膜表现出优越的紫外阻隔性和抗氧化性能。本研究结果为MNP应用于可食膜改性及食品包装提供了一定的理论依据。     

Effect of Soil Samples Preparation on Their Thermal Hydrophysical Properties and Allelotoxicity

Eurasian Soil Science - Changes in the properties of soil samples during drying or heating are known. However, the reasons for them have remained unclear up to this time. Our study aims to clarify...     

Effect of Microwave Heating of Kafirin on the Functional Properties of Kafirin Films

To improve the functional properties of cast kafirin films, dry kafirin, extracted with an aqueous ethanol‐based solvent at 70°C, was microwave‐heated. No effect on film tensile properties was found. Two strategies were employed to improve the effect of microwaving: extraction of kafirin using an aqueous tert‐butanol‐based solvent at ambient temperature to minimize temperature‐induced denaturation and wetting the kafirin to increase its dielectric properties. Microwave heating this kafirin to 90 or 96°C and holding for 1–2 min more than doubled maximum tensile strength and Young's modulus, and decreased strain by about one‐third compared with films made from nonmicrowaved kafirin. Film water vapor permeability was reduced by at least one‐third. Digestibility of microwaved kafirin and films was also substantially decreased, and film biodegradability was slowed slightly. Microwave heating gave a film microstructure with fewer and smaller size pores. SDS‐PAGE showed microwave‐induced intermolecular cross‐linking of the kafirin monomers, which was possibly responsible for the modification of film properties. Microwave heating of kafirin can be used to modify kafirin film properties, but the kafirin must be microwaved wet and be as close as possible to its native state.     

水土保持措施对土壤化学特性的影响

用物种多样性指数〔Shannon—wienner指数、Margalef’s指数、Simpson’s Doversity(l／Dominance)指数〕和均匀度指数(Evenness均匀度)和物种丰富度，对陕北黄土高原5种主要天然森林群落(油松林、山杨林、辽东栎林、白桦林、侧柏林)物种多样性进行了分析。结果表明，陕北黄土高原5种森林群落中山杨林物种多样性最高。植物生长型与物种多样性的关系表现为草本层的物种丰富度、多样性程度大于灌木层，灌木层大于乔木层；草本层均匀度与灌木层相差不明显，但二者显著大于乔木层。     

黑沙蒿根系抗拉特性及其与化学成分的关联性

[目的] 探讨根系抗拉特性与主要化学成分含量的关联性,以期充实根系固土力学特性研究以及提供矿区生态恢复和植物保护的理论支持。[方法] 以神东矿区广泛分布的多年生灌木黑沙蒿（Artemisia ordosica）为研究对象,利用TY8000伺服式强力机,研究1~4 mm径级直根段、含侧根分支处根段抗拉材料的力学特性并测定各径级的纤维素、半纤维素和木质素,研究根系材料力学及其与化学成分的关联性。[结果] ①随着根系直径增加,黑沙蒿直根段、含侧根分支处根段抗拉力增加,而抗拉强度和杨氏模量减小,且抗拉力、抗拉强度和杨氏模量都与根系直径呈幂函数关系。②直根段、含侧根分支处根段化学成分含量差异显著（p<0.05）,平均化学成分含量为：半纤维素（31.69%,32.18%） > 木质素（28.42%,25.30%） > 纤维素（15.50%,15.35%）。③随着根系直径增加,直根段纤维素含量减小,半纤维素和木质素含量增加,而含侧根分支处根段纤维素含量减小,半纤维素和木质素含量无变化。④直根段抗拉强度、杨氏模量与纤维素极显著正相关（p<0.01）,与半纤维素、木质素极显著负相关（p<0.01）。含侧根分支处根段抗拉强度、杨氏模量与纤维素极显著正相关（p<0.01）,与半纤维素、木质素无相关性。[结论] 黑沙蒿根系抗拉特性与化学成分表现出一定的相关性,且纤维素是影响灌木根系材料力学特性的主要化学组分。     

Improvement of Sorghum-Wheat Composite Dough Rheological Properties and Breadmaking Quality Through Zein Addition

Addition of sorghum flour to wheat flour produces marked negative effects on rheological properties of dough and loaf volume. Although there are notable differences in the chemical composition of sorghum proteins (kafirins) compared with wheat gluten that might imply poor functionality in breadmaking systems, a larger constraint may be the unavailability of kafirins due to encapsulation in protein bodies. In this study, zein, the analogous maize prolamin to kafirin, was used to determine the potential effects of protein-body-free prolamins on dough rheology and baking quality of wheat-sorghum composite flour. Mixograms run at 35°C (above the glass transition temperature of zein) were significantly (P < 0.01) improved with addition of zein. Mixogram peak heights increased while mixing time decreased uniformly with addition of zein. Dough extensibility studies showed an increase in maximum tensile stress, while baking studies showed an increase in loaf volume with increasing amounts of added zein. These data are supported by a previous study showing that, in a model system, zein mixed with starch can form viscoelastic networks, and suggest that kafirin, if made available, could contribute to dough formation.