Effect of acid and base treatments on structural,rheological, and antioxidant properties of α-zein

Five pH levels were experimented to study their effect on zein structural, rheological, and antioxidant properties. Structural changes, including secondary structures, surface charge, molecular weight, particle size distribution, and morphology were evaluated using a spectrum of instruments. Zein rheology, including the viscosity and viscoelastic property, was examined by a rheometer. The antioxidant efficacy was determined by measuring the scavenging activity of 1,1-diphenyl-2-picrylhydrazyl free radical and the reducing power of 1,10-phenanthroline-iron with a spectrophotometer. Results indicated that under proper acidic or basic conditions, zein structures, rheological behaviour, and antioxidant properties changed significantly. Decreased contents for α-helix, β-sheet, and β-turn were detected by the Fourier transform infrared spectroscopy for zein samples at acidic and basic conditions comparing to those in a near neutral condition, which were attributed to the deamidation of glutamine to glutamic acid/glutamate in zein. However, no obvious zein fragmentation or oligomerization was detected by the sodium dodecyl sulfate–polyacrylamide gel electrophoresis. The mild deamidation without fragmentation led to a decreased viscosity and an improved antioxidant property of zein. Modified rheological behaviour and enhanced antioxidant properties resulting from a pH treatment may facilitate novel application development of zein in food and pharmaceutical industries.     

Influence of drying temperature on the solubility,the purity of isolates and the electrophoretic patterns of corn proteins

A sequential extraction of proteins from whole corn kernels dried between 54 and 130 °C was performed in order to elucidate the effect of the drying temperature on the solubility, the purity and the electrophoretic patterns of the different classes of corn proteins. It was observed that albumin, globulin and zein solubilities dropped significantly when the drying temperature increased, while fractions solubilised as glutelin-G₂ and glutelin-G₃ increased until 110 °C before dropping slightly at 130 °C. The analysis of the solubility of different protein groups indicated that mechanisms other than the creation of new disulfide bonds between proteins occurred during the high temperature drying of corn. Except for glutelin-G₁ and zein isolates, which were highly pure, the purities of albumin, globulin, glutelin-G₂ and glutelin-G₃ isolates after dialysis were influenced by the drying temperature. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) showed the disappearance of some water and salt-soluble polypeptides at high drying temperatures. The electrophoretic patterns of zein and glutelin-G₁ were not significantly modified, although the solubility of zein was affected by the drying temperature.     

Extensional flow,viscoelasticity and baking performance of gluten-free zein-starch doughs supplemented with hydrocolloids

Viscoelastic doughs of zein and starch were prepared at 40 °C, above the glass transition temperature of zein. The effects of hydrocolloid supplementation with hydroxypropyl methylcellulose (HPMC) or oat bran with a high content of β-glucan (28%) were investigated by dynamic measurements in shear, confocal laser scanning microscopy (CLSM) and Hyperbolic Contraction Flow. Zein-starch dough without hydrocolloids exhibited rapid age-related stiffening, believed to be caused by cross-links between peptide chains. A prolonged softness was attributed to doughs containing hydrocolloids, with the oat bran exhibiting the most pronounced reduction in age-related stiffening. Moreover, CLSM-images of dough microstructure revealed that a finer fibre network may be formed by increased shearing through an addition of viscosity-increasing hydrocolloids, a reduction in water content in the dough or the use of appropriate mixing equipment. The Hyperbolic Contraction Flow measurements showed that doughs containing hydrocolloids had high extensional viscosities and strain hardening, suggesting appropriate rheological properties for bread making. Zein-starch dough without hydrocolloids showed poor bread making performance while hydrocolloid additions significantly improved bread volume and height. Although the hydrocolloid supplemented doughs had similar extensional rheological properties and microstructures, a fine crumb structure was attributed only to bread containing HPMC, marking the importance of surface active components in the liquid-gas interface of dough bubble walls. Zein could not mimic the properties of gluten on its own, but hydrocolloids did positively affect the structural and rheological properties of zein, which yielded dough similar to wheat dough and bread with increased volume.     

玉米醇溶蛋白的研究及应用

玉米醇溶蛋白是玉米中主要的贮藏蛋白,约占所有蛋白的45～50%.玉米醇溶蛋白具有很强的韧性、疏水性、可降解性、抗菌性等特点,广泛用于食品、医药、纺织、造纸等工业.     

添加剂改性玉米醇溶蛋白复合膜的制备与表征

采用流延法制备高含量玉米醇溶蛋白（Zein）的Zein/壳聚糖（CS）复合膜，通过复合添加剂〔m(甘油)：m(聚乙二醇400)=1:1〕对Zein/CS复合膜共混改性，研究复合添加剂添加量（以总溶液质量计，分别为0、0.5%、1.0%、1.5%、2.0%）对薄膜的力学、光学和热学性能等的影响，并通过SEM、FTIR对薄膜形貌和结构变化进行表征。结果表明，复合添加剂通过削弱Zein和CS之间的分子间作用力，达到增塑效果，薄膜综合机械性能有所改善，随着复合添加剂添加量的升高，薄膜断裂伸长率逐渐增强，拉伸强度呈下降再上升的趋势；水蒸气透过率逐渐增加，水接触角逐渐减小，薄膜亲水性随之增强。与不含复合添加剂的薄膜（ZC-0）相比，当复合添加剂添加量为1.5%时，复合膜（ZC-1.5）的抗拉强度降低了27.40%，断裂伸长率增长了39.87%，水蒸气透过率上升了29.10%。通过SEM和DSC观察，添加复合添加剂改性后，改善了Zein和CS之间的相容性，制备的薄膜表面更加平整光滑。综合性能可得，制备高含量Zein的Zein/CS复合膜，复合添加剂浓度为1.5%时，薄膜性能最优。并在含有1.5%复合添加剂的Zein/CS薄膜中添加了一定量的姜黄素，据测定其能够有效提高薄膜的抗氧化性能至55.18%。     

Zein nanoparticles produced by liquid–liquid dispersion

Variables during production of zein nanoparticles using a liquid–liquid dispersion process were researched in this work for the potential development of food-grade nanoscalar delivery systems. The process was based on dissolving zein in 55–90% aqueous ethanol, followed by shearing the stock solutions into deionized water. The size of zein nanoparticles was typically 100–200 nm, and smaller particles were formed at a higher shear rate, and a higher ethanol concentration or a lower zein concentration in stock solutions. The addition of 1% zein nanoparticles into 0.5% carboxymethylcellulose solutions (adjusted to pH 3–9) increased the viscosities of the polymer solutions, and the increase was found to be larger at higher pH. The results showed that liquid–liquid dispersion is a simple and scalable process to manufacture nanoscalar delivery systems of many bioactive compounds. However, physical properties of eventual food products are to be examined for the potential influence of the added delivery systems.     

玉米醇溶蛋白用作药物输送系统载体的研究进展

玉米醇溶蛋白(Zein)是一种天然可食性植物大分子,具有可再生性、无毒性、两亲性及良好的生物相容性和生物可降解性,可通过自组装形成微球或纳米粒。近年来,Zein用作药物输送系统(drug delivery system,DDS)载体材料成为研究热点,可通过Zein的自组装特性将药物包载在其内部获得Zein-DDS微粒。本文简述了Zein的特性及其作为DDS载体的优势,总结了Zein-DDS的制备方法、性能及Zein的修饰改性研究进展,指出Zein具有较强的疏水性和抗胃酸分解特性,Zein-DDS可有效地提高药物稳定性、延缓药物释放及增强药物靶向性。因此,Zein用作DDS的载体具有广阔的应用前景,今后的研究工作将会在拓宽研究领域、改进制备方法及Zein的修饰改性等方面展开。     

Incorporating phenolic compounds opens a new perspective to use zein films as flexible bioactive packaging materials

To eliminate their classical brittleness and flexibility problems zein films were plasticized by incorporation of different phenolic acids (gallic acid (GA), p-hydroxy benzoic acid (HBA) or ferulic acids (FA)) or flavonoids (catechin (CAT), flavone (FLA) or quercetin (QU)). The use of GA, CAT, FA and HBA at 3 mg/cm² eliminated the brittleness of films and gave highly flexible films showing elongations between 135% and 189%, while FLA and QU caused no considerable effect on film elongation. The films containing FA and HBA showed extreme swelling and lost their structural integrity when hydrated in distilled water. In contrast, CAT and GA containing films maintained their integrity following hydration. Most of the GA (up to 93%) and a considerable portion of CAT (up to 60%) in the films existed in soluble form. Therefore, the films showed antioxidant and/or antimicrobial activity. The TEACs of soluble phenolic compounds in 3 mg/cm² CAT and GA containing films were 21.0 and 86.2 ??mol trolox/cm², respectively. The GA containing films showed antimicrobial activity on Listeria monocytogenes and Campylobacter jejuni, while CAT showed no antimicrobial activity on these bacteria at the studied concentration. This work opens a new perspective for using zein in flexible bioactive packaging.     

玉米醇溶蛋白/多糖基复合抗菌膜的制备及性能表征

为了提升玉米醇溶蛋白（Zein）的应用价值,改善传统石油基对环境造成的污染。研究以Zein、琼脂（Agar,AG）和卡拉胶（Carrageenan,CA）为成膜基材,明胶为增强剂、甘油增塑剂,纳他霉素和乳酸链球菌素为抗菌剂通过流延的方式来制备复合抗菌膜,并对其理化性能及保鲜效果进行了研究。结果表明,三种复合抗菌膜中Zein-AG膜的机械性能和光学性能较高,机械强度为7.12±0.91 MPa、透光率为25.40±1.00%;Zein-AG膜的透气性和水溶性较高;Ze-CA/AG膜的抑菌性能强,与其他复合膜相比具有显著性差异（P<0.05）,其中对黑曲霉及根霉的抑菌圈直径为35.155±0.85 mm和23.17±0.94 mm,并且还能有效地抑制金黄色葡萄球菌和大肠杆菌的繁殖。在保鲜方面,Ze-CA/AG膜对于葡萄的失重率、硬度及营养指标的控制上呈现了较好的效果,有利于延长葡萄的保鲜期。研究为拓宽Zein的开发与利用及在制备绿色环保包装材料的研究上提供了参考依据。     

负载花椒精油的玉米醇溶蛋白-柑橘果胶乳液性能评价

目的 研发出一款新型的花椒精油Pickering乳液,为花椒精油Pickering乳液的制备和花椒精油应用场景的拓宽提供参考。方法 以花椒精油为油相,玉米醇溶蛋白-柑橘果胶复合纳米粒子为固体颗粒,制备花椒精油Pickering乳液。研究复合纳米粒子质量浓度(20、25、30、35、40 g/L)对Pickering乳液粒径、电位、微观结构、稳定性、流变特性等理化性能和抗氧化性能、抑菌性能等功能活性的影响。结果 随着复合纳米粒子浓度的提高,乳液的粒径呈先降后增趋势,ζ-电位绝对值、包埋率则呈先增后降趋势,当质量浓度为35 g/L的时候,乳液粒径最小为1 900.3 nm、ζ-电位和包埋率最大分别为32.7 mV、95%;此浓度下乳液贮藏稳定性最好,且具有优异的温度稳定性,在酸性(pH=2、3、4)和碱性环境(pH=8、9)下稳定性表现良好;所有乳液均显现出明显的剪切变稀行为,属于假塑性流体;在低频下乳液损耗模量大于储能模量,呈流体状态;相较于花椒精油,负载花椒精油的Pickering乳液的抗氧化性能和抑菌性能得到了显著提高。结论 复合纳米粒子质量浓度为35 g/L时制备的负载花椒精油Pickering乳液具有较好的稳定性、抗氧化和抑菌性能。