Investigation of surface properties of physico-chemically modified natural fibres using inverse gas chromatography

Inverse gas chromatography (IGC) is a suitable method to determine surface energy of natural fibres when compared to wetting techniques. In the present study, the surface properties of raw and modified lignocellulosic fibres have been investigated by IGC. The fibres chosen for the study were flax, hemp, kenaf, agave, agave hybrid, sisal and pineapple. The treatments used were 4% NaOH and 2% zein. The uniqueness of zein treatment is that it is bio-based and therefore maintains the biodegradable character of the natural fibres. Fourier transform infrared spectroscopy (FTIR) and environmental scanning electron microscope (ESEM) were also performed to characterize the surface changes in fibres. The surface properties of fibres are influenced by the chemical composition, crystallinity and morphology of the fibres. Bast fibres exhibited higher surface dispersive energy than leaf fibres. The raw fibres have a predominant basic character, whereas the alkaline treatment makes the fibres more acidic. Both alkaline and zein treatments decrease the dispersive surface energy and the specific free energy of adsorption.     

玉米醇溶蛋白膜的制备研究

[目的]研究用玉米醇溶蛋白制作的可食包装膜。[方法]以玉米醇溶蛋白为主要原料,一定浓度的乙醇作为溶液,甘油和油酸用作增塑剂,研究增塑剂用量、挤压力度、制备温度对玉米醇溶蛋白膜强度的影响,以质构仪膜穿刺数据为评价指标,比较了不同条件对玉米醇溶蛋白膜强度的影响。[结果]优化结果表明,乙醇溶液浓度80%、油酸20%(与醇溶蛋白的质量比),压力10 MPa,水浴温度70℃时制备的玉米醇溶蛋白膜柔韧性和强度较好。[结论]在优化条件下,玉米醇溶蛋白可作为一种可食材料制作包装膜。     

玉米醇溶蛋白硬胶囊的制备工艺研究

[目的]优化玉米醇溶蛋白硬胶囊的制备工艺。[方法]以玉米黄粉提取的醇溶蛋白为原料,在p H 6.5、干燥温度65℃的最佳条件下,以羟丙基纤维素、聚乙烯吡咯烷酮、山梨醇、甘油、乙醇浓度为考察因素进行单因素试验,在单因素试验基础上,以羟丙基纤维素、聚乙烯吡咯烷酮、山梨醇、甘油4个因素作为自变量,进行4因素3水平正交试验,通过检测胶囊的成品率、脆碎度和崩解时限等指标,确定制备硬胶囊的较优工艺。[结果]玉米醇溶蛋白硬胶囊最佳成囊效果为95%乙醇溶液700μL、羟丙基纤维素0.20 g、聚乙烯吡咯烷酮0.60 g、20%山梨醇60μL、20%甘油50μL。[结论]在最佳优化条件下制备出的玉米醇溶蛋白硬胶囊成膜性好,检测的成品率、脆碎度、崩解时限所得结果均符合相关标准。     

Similarities and differences in secondary structure of viscoelastic polymers of maize α-zein and wheat gluten proteins

The secondary structure of a dough-like zein polymer was compared to the structure present in a wheat viscoelastic system using FT-IR spectroscopy. When zein was mixed at 35 °C, which is above its glass transition temperature (T_g), changes in its secondary structure suggested that the protein loses its native structure, mainly composed of α-helices (68%), and a viscoelastic system is formed by a structural rearrangement that favors β-sheet structures. This rearrangement is very similar to the structural changes observed in gluten viscoelastic polymers. Upon removal of shear stress, the zein polymer showed a rapid decrease in the proportion of β-sheet structures (from 48% to 28% after the first 3 min) in favor of unordered structures. At the same time, the viscoelasticity of the polymer decreased rapidly. In contrast, gluten, in a similar viscoelastic system and held at the same temperature, showed a fairly constant high content of β-sheet structures (49%) coinciding with the slow relaxation time typical of gluten networks after the removal of shear. We speculate that the addition of a protein capable of causing extensive and stable β-sheet formation in the zein–starch viscoelastic polymer could increase the stability and relaxation time of the zein system and, thereby, create the possibility of a zein dough with similar functionality to a wheat viscoelastic system.     

玉米优势类群划分及其杂交模式的研究——过氧化物酶、酯酶和醇溶蛋白多态性的聚类分析

选用３６个优良玉米自交系，组配了３００个杂交种（其中７８个杂交种为１３个自交系按完全双列杂交设计组配），利用过氧化物酶、酯酶和醇溶蛋白多态性的综合分析，划分了我国玉米的优势类群，所得结果与材料的血缘和育种实践高度吻合。研究结果表明，我国的优势杂交模式为美国杂交种选系×四平头系等六类，综合遗传距离与特殊配合力和杂种产量的关系均为抛物线关系，相关系数分别为０．６３２＊＊和０．６７１＊＊。还对优势类群在育种上的利用提供了参考意见。     

郑58/opaque2近等基因系中opaque2基因突变位点分析与高效分子标记开发

opaque2突变体材料是最常用的高赖氨酸玉米供体。对已获得的郑58/o2近等基因系研究表明,胚乳发育不同时期22-kDα-醇溶蛋白的积累均明显低于郑58。荧光定量PCR结果表明,α-醇溶蛋白家族基因Z1A、Z1B、Z1C和Z1D的表达均显著低于郑58。郑58/o2胚乳发育不同时期Opaque2基因均正常表达。测序分析发现,郑58/o2中o2基因ATG后713 bp处缺失10个碱基,ORF预测Opaque2蛋白翻译提前终止。针对突变缺失位点开发基因内分子标记o2-indel-1,利用该标记进行回交转育,结果表明,o2-indel-1与o2突变表型完全连锁,错选率为0。opaque2基因突变位点的解析有助于高效分子标记的开发,有效降低错选率,提高优质蛋白鲜食玉米多基因聚合育种的选择效率。     

Oxidation of commercial (α-type) zein with hydrogen peroxide improves its hydration and dramatically increases dough extensibility even below its glass transition temperature

To improve the rheological properties of zein doughs, α-type zein and zein-starch doughs were prepared with the oxidising agents, hydrogen peroxide and peroxidase, which strengthen gluten-based doughs by cross-linking. Hydrogen peroxide and peroxidase increased zein dough extensibility compared to preparation with water. Hydrogen peroxide prepared zein doughs were extensible and cohesive below zein’s glass transition temperature. The doughs did not exude water and maintained flexibility when stored. Confocal laser scanning microscopy revealed that in zein-starch doughs prepared with hydrogen peroxide a thin continuous zein matrix was formed around the starch granules, whereas doughs prepared with water exhibited clumps of granules. SDS-PAGE of zein doughs and films treated with the oxidising agents showed no evidence of zein polymerisation, nor did Fourier transform infrared spectrometry reveal any significant changes in secondary structure. Further, hydrogen peroxide treatment did not increase zein film glass transition temperature, but it did increase transition enthalpy, and film water uptake increased with hydrogen peroxide concentration. The greatly increased extensibility of hydrogen peroxide prepared zein doughs and their improved water-holding are not due to oxidative cross-linking. It is proposed that the effects are primarily due to hydroxylation of amino acid aliphatic side chains, improving hydration through hydrogen bonding.     

Aggregate formation of zein and its structural inversion in aqueous ethanol

Zein is a prolamine of maize. Conventionally, 70–90% aqueous ethanol is used to dissolve zein. When the hydrodynamic radii of zein molecules in aqueous ethanol were monitored with a dynamic light scattering instrument, it was found that zein aggregates in the solvent and the degree of aggregation depends on the composition of the solvent mixture. As the ethanol content of solvent increased from 70% to 90%, the aggregation number of zein molecules decreased from 10,000 until it reached a minimum. The aggregation number then increased abruptly to greater than 10,000 as the ethanol content of the solvent mixture increased to 92%. Since zein has amphiphilic characteristics, this behavior was interpreted as the formation of a micelle-like structure in its solution whereby ca. 90% ethanol that showed minimum aggregation number is regarded as a structural inversion point. This point of view was supported by a simple experiment that showed selective interaction of zein molecules with hydrophilic or hydrophobic particles.     

两种植物蛋白肠衣膜的制备及理化性质比较研究

[目的]研究利用植物蛋白制备可食肠衣膜的技术方法,并对蛋白膜理化性质进行分析比较,优选更适合制备肠衣的蛋白膜。[方法]以天然植物蛋白(玉米醇溶蛋白、大豆分离蛋白)为原料,适当加入添加剂甘油、谷氨酰胺转氨酶等,增强延展性和柔韧性,分别采用机械挤压法和流延法制备植物蛋白肠衣膜。以质构仪穿刺数据为评价指标,比较不同工艺条件对肠衣膜强度的影响,并对比2种植物蛋白肠衣膜的理化性质。[结果]谷氨酰胺转氨酶酶解后流延法制备的大豆分离蛋白肠衣膜的蛋白含量、含水率以及穿刺强度分别达到70.2%、11.8%以及0.632 kg,各项指标高于挤压法制备的玉米醇溶蛋白肠衣膜。[结论]大豆分离蛋白较玉米醇溶蛋白更适合制备成肠衣膜。     

玉米醇溶蛋白微球制备条件的探索以及体外释药行为研究

以玉米醇溶蛋白（zein）为原料，采用相分离法制备微球，探讨了乙醇的浓度，zein的浓度以及第二溶剂（水）加入的速度对蛋白微球大小的影响；采用压片方法获得了包被模型药物（伊维茵素IVM）的蛋白微球片剂，研究了该微球片剂的体外释放动力学以及释放后微球结构的变化。结果表明：微球粒径大小与乙醇及玉米醇溶蛋白的最终浓度、第二溶剂的加入速度有关。迅速加入第二溶剂才能获得粒径比较均匀的蛋白微球；乙醇的最终浓度在40％时可以获得粒径1μm左右的微球；微球的大小随着zein的最终浓度的增加而增大。该蛋白微球新剂型改善了载药微球悬浮液的稳定性。抑制了释药初期的突释现象。