Preparation and characterization of nanoparticles containing trypsin based on hydrophobically modified chitosan

Trypsin was immobilized on linolenic acid modified chitosan using glutaraldehyde (GA) as cross-linker, which was confirmed by Fourier transform infrared (FTIR) spectra. The chitosan nanoparticles containing trypsin (TR) can be prepared after the sonication of immobilized trypsin. The GA concentration affected both the enzyme activity of the nanoparticle and particle size. Results indicated that the activity of trypsin immobilized onto linolenic acid modified chitosan nanoparticles increased with increasing concentration of GA up to 0.07% (v/v) and then decreased with increasing amount of GA. On the other hand, particle size increased (from 523 to 1372 nm) with the increasing concentration of GA (from 0.03 to 0.1% v/v). The enzyme catalytic characteristics of nanoparticle solution were also studied. The results showed that the kinetic constant value (K(m)) of TR immobilized on nanoparticle (71.9 mg/mL) was higher than that of pure TR (50.2 mg/mL). However, the thermal stability and optimum temperature of TR immobilized on nanoparticles improved, which make it more attractive in the application aspect.     

Preparation, characteristics, and stability of glutathione-loaded nanoparticles

The aim of this study was to investigate the characteristics and oxidative stability of chitosan-glutathione conjugate (CS-GSH) and CS-GSH nanoparticles (CS-GSH NPs) to explore the potentials of these nanoparticle systems for GSH delivery. CS-GSH was synthesized using a radical polymerization method, and CS-GSH NP was prepared by ionic gelation of CS-GSH with sodium tripolyphosphate (TPP). The sizes of CS-GSH NPs significantly increased with increasing CS-GSH concentration and CS-GSH/TPP ratio. The entrapment efficiency (EE) significantly increased with increasing CS-GSH concentration and significantly decreased with increasing CS-GSH/TPP ratio. The immobilized GSH could be protected against oxidation compared to free GSH. The thiol content in the nanoencapsulated GSH was more effectively maintained than those in free GSH and CS-GSH, regardless of the presence of oxidative stress-inducing agents. These results suggest that CS-GSH NP can be used to enhance the oxidative stability of GSH.     

Concentrations of low and high molecular weight thiols in wheat dough as affected by different concentrations of ascorbic acid

Different amounts of ascorbic acid (AA) were added to flour, and the concentrations of low and high molecular weight thiols in the dough were determined. For the determination of the low molecular weight thiols, glutathione, cysteine, and the corresponding disulfides, an isotope dilution assay with a (14)C-labeled internal standard was used. For the determination of the high molecular weight thiols, a method was developed that involved derivatization of dough with Ellman's reagent, removal of excess reagent by dialysis, micro-Osborne fractionation, release of the label by reduction, and determination of reduced Ellman's reagent by reversed-phase high-performance liquid chromatography. Mixing of flour without AA led to a decrease of the glutathione and an increase of the cysteine concentration. Addition of AA reduced the concentration of both thiols to a minimum when 125 mg of AA/kg of flour was applied. Furthermore, the concentrations of high molecular weight thiols in the glutenins of flours from different wheat cultivars were determined. The values ranged from 5.6 to 8.2 micromol/kg of protein and showed a correlation between flour quality and SH concentration. On addition of AA and mixing of a dough, the concentrations of the protein thiols in the glutenins isolated from the dough increased to a maximum when 100 mg of AA/kg of flour was added. Higher concentrations of AA led to a decrease of the SH concentration. The last results are not in accordance with previously published data or with current hypotheses about the mechanism of the AA improver action.     

Stability of citral in emulsions coated with cationic biopolymer layers

Multilayer emulsions containing citral were prepared by the layer-by-layer deposition technique based on the electrostatic interaction between negatively charged emulsion droplets and two positively charged biopolymer coatings, chitosan (CS) and ε-polylysine (EPL). The optimum concentrations of both CS and EPL were determined through the ζ-potential and particle size measurements and were found to be 1.5 mg/mL for CS and 6 mg/mL for EPL. Quartz crystal microbalance with dissipation monitoring (QCM-D) was conducted to monitor the binding between emulsion droplets and cationic polymers, and our results proved the existence of strong interactions between emulsions and the cationic polymer coatings. The stability of citral and the production of the off-flavor compounds were analyzed by solid-phase microextraction gas chromatography (SPME-GC). The results suggested that the addition of the cationic CS interfacial layer was effective in improving the stability of citral during storage.     

Optimization of fabrication parameters to produce chitosan-tripolyphosphate nanoparticles for delivery of tea catechins

This work investigated the polyanion-initiated gelation process in fabricating chitosan-tripolyphosphate (CS-TPP) nanoparticles intended to be used as carriers for delivering tea catechins. The results demonstrated that the particle size and surface charge of CS-TPP nanoparticles could be controlled by fabrication conditions. For preparation of CS-TPP nanoparticles loaded with tea catechins, the effects of modulating conditions including contact time between CS and tea catechins, CS molecular mass, CS concentration, CS-TPP mass ratio, initial pH value of CS solution, and concentration of tea catechins on encapsulation efficiency and the release profile of tea catechins in vitro were examined systematically. The study found that the encapsulation efficiency of tea catechins in CS-TPP nanoparticles ranged from 24 to 53%. In addition, FT-IR analysis showed that the covalent bonding and hydrogen bonding between tea catechins and CS occurred during the formation of CS-TPP nanoparticles loaded with tea catechins. Furthermore, studies on the release profile of tea catechins in vitro demonstrated that the controlled release of tea catechins using CS-TPP nanoparticles was achievable.     

Linolenic acid-modified chitosan for formation of self-assembled nanoparticles

Chitosan was modified by coupling with linolenic acid through the 1-ethyl-3-(3-dimethylaminopropyyl)carbodiimide-mediated reaction. The degree of substitution was measured by 1H NMR, and it was 1.8%, i.e., 1.8 linolenic acids group per 100 anhydroglucose units. The critical aggregation concentration (CAC) of the self-aggregate of hydrophobically modified chitosan was determined by measuring the fluorescence intensity of the pyrene as a fluorescent probe. The CAC value in phosphate-buffered saline (PBS) solution (pH 7.4) was 5 x 10(-2) mg/mL. The average particle size of self-aggregates of hydrophobically modified chitosan in PBS solution (pH 7.4) was 210.8 nm with a unimodal size distribution ranging from 100 to 500 nm. A transmission electron microscopy study showed that the formation of near spherical shape nanoparticles had enough structural integrity. The loading ability of hydrophobically modified chitosan (LA-chitosan) was investigated by using bovine serum albumin (BSA) as a model protein. Self-aggregated nanoparticles exhibited an increased loading capacity (19.85 +/- 0.04 to 37.57 +/- 0.25%) with an increasing concentration of BSA (0.1-0.5 mg/mL).     

玉米醇溶蛋白-壳聚糖纳米营养递送粒子的制备及性质

利用蛋白质和多糖构建纳米营养递送载体,是提高食品活性物质稳定性及利用率的重要手段。为了构建具有缓释特性的纳米营养递送体系,该研究以玉米醇溶蛋白（zein）为基材,构建玉米醇溶蛋白-壳聚糖纳米营养递送体系,以姜黄素（Cur）为营养模型,探究了壳聚糖分子量、zein与壳聚糖质量比对纳米粒子及其负载Cur性能的影响,通过扫描电子显微镜（Scanning Electron Microscope,SEM）、傅里叶红外光谱（Fourier Transform Infrared Spectroscopy,FTIR）等方法表征其结构,阐明复合纳米粒子形成机制,探讨其稳定性和缓释性能。结果表明：不同分子量的壳聚糖对纳米粒子的粒径、多分散性指数和zeta电位有影响。高分子量壳聚糖的加入可使纳米粒子粒径减小,且更加稳定。在zein与高分子量壳聚糖质量比为8∶1时,制备纳米粒子粒径较小（80.13 nm）,其zeta电位为46.18 mV;在此条件下,当姜黄素添加量为1.0%时,其包封率和负载量分别为82.93%和8.29%;通过SEM观察,纳米粒子呈球形,分布均匀;氢键及静电相互作用是组装该纳米粒子的作用力;壳聚糖的引入提高了纳米粒子的pH值、离子及储藏稳定性,扩展了其应用范围;与游离的姜黄素相比,纳米营养递送粒子呈现明显的缓释特性。研究结果为构建具有缓释特性的营养递送体系提供了理论基础。     

A modified chemical procedure for rapid determination of glucosamine and its application for estimation of mold growth in peanut kernels and koji.

One-step hydrolysis of chitin to release glucosamine for quantitation was achieved by combining a chitin-containing sample (10-200 mg of sample size) in a test tube with 1 mL of 10 M HCl followed by vacuum treatment for 10 min, incubation at 28 degrees C for 30 min, replenishment with 3 mL of deionized water, nitrogen flushing, screw capping, and heat treatment at 140 degrees C for 60 min. A phosphate buffer solution (pH 12.5, 0.2 M) was effective in pH stabilization and enhancing colorimetric determination of glucosamine content. When the modified procedure was applied to analyze glucosamine content in the mycelia of various molds, glucosamine content varied mainly depending on mold species. In estimations of mold growth of the uninoculated peanut kernels incubated under a humidified condition for 5 weeks, cooked rice and soybean inoculated with conidia of Aspergillus oryzae for koji preparation, logarithms of the internal mold populations and glucosamine contents both increased with increases of incubation time. The modified procedure provided a rapid and reliable estimation of mold growth in various substrates.     

磁性壳聚糖微球吸附苹果汁有机酸的动力学及热力学特性

为充分利用中国丰富的苹果资源,开发多品类的苹果深加工产品,以磁性壳聚糖微球为吸附剂,通过磁分离技术,吸附获得苹果汁中的天然有机酸,并对其吸附过程进行研究。利用Lagergren准一级动力学方程、准二级动力学方程、Elovich方程及内扩散方程对吸附反应动力学过程进行拟合;利用Langmuir等温吸附模型、Freundlich等温吸附模型及Temkin等温吸附模型对吸附等温数据进行拟合,并对其吸附反应热力学特性进行分析。通过比较线性拟合方程的决定系数,发现磁性壳聚糖微球吸附苹果汁中有机酸的动力学过程更加符合Lagergren准二级动力学模型,吸附温度越高,吸附速率常数和初始吸附速率越大,但平衡吸附量越低。等温吸附过程更加符合Langmuir等温吸附模型,表明该吸附过程更趋向于单分子层的化学吸附。298 K时,有机酸的饱和吸附量可达到188.679 2 mg/g,表明磁性壳聚糖微球是苹果汁中有机酸的1种高效吸附剂。热力学参数ΔG°0,ΔH°0,ΔS°0,表明磁性壳聚糖微球对苹果汁有机酸的吸附过程为熵增加的可自发进行的放热过程。动力学及热力学结果为磁性壳聚糖微球吸附苹果汁有机酸的研究提供了理论基础与技术支持。     

聚丙烯酸接枝碱木质素基铁肥的制备及其缓释性能

为提高铁元素的累积释放率,以丙烯酸单体接枝无定形高分子碱木质素制备了具有保水、缓释功能的聚丙烯酸接枝碱木质素基铁肥(简写,ALS-G-P(AA)铁肥)。考察了丙烯酸中和度、引发剂用量、交联剂用量、温度、碱木质素接枝率等因素对ALS-G-P(AA)铁肥吸水倍率的影响,研究了ALS-G-P(AA)铁肥在水中的Fe离子的缓释行为。结果表明:最佳制备条件为丙烯酸中和度60%、引发剂用量0.06g、交联剂用量0.03g、温度为60℃、碱木质素接枝率为25%;该产物铁质量分数为7.74mg/g,吸水倍率可达1017g/g。吸水饱和的ALS-G-P(AA)铁肥的肥效期为22d,其在水中铁元素累积溶出特征符合一元二次方程模型,铁元素释放曲线呈"S"形。该研究为高效施用铁肥和碱木质素在农业可降解缓/控释载体领域的应用提供了参考,并有望进一步拓展。     

Nanoparticles synthesized from soy protein: preparation, characterization, and application for nutraceutical encapsulation

Nanoparticles were synthesized from soy protein, one of the most abundant and widely utilized plant proteins, for nutraceutical and drug encapsulation. The preparation process consisted of dispersion, desolvation, drug incorporation, cross-linking, and evaporation. The role of each procedure in the formation of nanoparticles was systematically investigated by means of particle size, size distribution, and zeta potential as well as morphology observation. Curcumin as a model drug was encapsulated successfully into the nanoparticles, evidenced by Fourier transform infrared spectroscopy and X-ray diffraction patterns. The average size of the curcumin-loaded nanoparticles was 220.1 to 286.7 nm, and their zeta potential was around -36 mV. The highest encapsulation efficiency and loading efficiency achieved were 97.2% and 2.7%, respectively. The release of curcumin in phosphate buffer saline followed a biphasic pattern. Possible mechanisms of the formation of soy protein nanoparticles as well as the incorporation of curcumin were discussed based on the data obtained from this study.     

菜籽蛋白加工废液中多酚和多糖同步提取工艺优化

为开发利用菜籽蛋白加工废液中的生理活性物质,该研究在单因素试验基础上,采用Box-Behnken响应面试验设计法,对菜籽蛋白加工废液中多酚和多糖提取工艺条件进行优化,同时探究两种物质的体外抗氧化活性。结果表明,影响菜籽蛋白加工废液中多酚和多糖得率的因素大小顺序为:乙醇体积分数浸提温度浸提时间,最佳提取工艺为:浸提温度60℃、乙醇体积分数65%、浸提时间31 min,在此条件下多酚得率为2.19%,多糖得率为8.14%;多酚提取物对DPPH·具有较强清除能力,其半抑制质量浓度为0.20 mg/mL,多糖提取物对DPPH·和·OH均具有较强的清除能力,其半抑制质量浓度分别为1.45、2.38 mg/mL;高效液相色谱法初步检测表明,菜籽蛋白加工废液中含有香豆酸、丁香酸、对香豆酸、芥子酸和苯甲酸。研究结果为菜籽蛋白加工废液的再利用提供参考。     

高密度CO2处理虾肌球蛋白形成凝胶的临界浓度与凝胶强度

为了探讨高密度CO_2(dense phase carbon dioxide,DPCD)诱导蛋白质形成凝胶的机制,以凡纳滨对虾肌球蛋白为研究对象,研究了DPCD处理压强、温度和时间对虾肌球蛋白形成凝胶的临界浓度和对虾肉糜凝胶强度的影响。研究结果表明:DPCD处理压强和温度对虾肌球蛋白溶液形成凝胶的临界浓度有显著影响,处理时间对肌球蛋白溶液形成凝胶的临界浓度无显著影响,但增加处理时间,可以形成更加紧实的凝胶。在40℃和5~30 MPa时虾肌球蛋白溶液形成凝胶的临界质量浓度为14 mg/mL,在50℃和5、10 MPa时虾肌球蛋白溶液形成凝胶的临界质量浓度为12 mg/mL,在50℃和15~30 MPa时虾肌球蛋白溶液形成凝胶的临界质量浓度为11 mg/mL,在60℃和5~30 MPa时虾肌球蛋白溶液形成凝胶的临界质量浓度为10 mg/mL。DPCD处理压强和温度对虾肉糜的凝胶强度也具有显著影响(P0.05),且随着压强增加和温度升高,虾肉糜凝胶强度呈增加趋势(P0.05);在50℃和25 MPa下处理虾肉糜20 min,形成的凝胶强度较好,达到了(14.28±0.57)N·mm。DPCD处理温度越高,虾肌球蛋白形成凝胶的临界浓度就越低,而虾肉糜形成凝胶的强度越高;DPCD处理压强越高,虽然对虾肌球蛋白形成凝胶的临界浓度影响较小,但能使虾肌球蛋白和虾肉糜形成凝胶的强度增加。从分析中还可以推断,DPCD低压(5~10 MPa)诱导虾肉糜形成凝胶主要是热效应的作用,DPCD较高压强(10 MPa)诱导虾肉糜形成凝胶是热和CO_2分子效应的共同作用。研究结果为进一步阐明DPCD诱导蛋白质形成凝胶的机制提供了基础数据。     

Influence of environmental stresses on stability of O/W emulsions containing cationic droplets stabilized by SDS-fish gelatin membranes

Oil-in-water (O/W) emulsions containing small oil droplets (d32 approximately 0.22 microm) stabilized by sodium dodecyl sulfate (SDS)-fish gelatin (FG) membranes were produced by an electrostatic deposition technique. A primary emulsion containing anionic SDS-coated droplets (zeta approximately -40 mV) was prepared by homogenizing oil and emulsifier solution using a high-pressure valve homogenizer (20 wt % corn oil, 0.46 wt % SDS, 100 mM acetic acid, pH 3.0). A secondary emulsion containing cationic SDS-FG-coated droplets (zeta approximately +30 mV) was formed by diluting the primary emulsion with an aqueous fish gelatin solution (10 wt % corn oil, 0.23 wt % SDS, 100 mM acetic acid, 2.00 wt % fish gelatin, pH 3.0). The stabilities of primary and secondary emulsions with the same oil concentration to thermal processing, ionic strength, and pH were assessed by measuring particle size distribution, zeta potential, microstructure, destabilized oil, and creaming stability. The droplets in secondary emulsions had good stability to droplet aggregation at holding temperatures from 30 to 90 degrees C for 30 min, [NaCl] < or = 100 mM, and pH values from 3 to 8. This study shows that the ability to generate emulsions containing droplets stabilized by multilayer interfacial membranes comprised of two or more types of emulsifiers, rather than a single interfacial layer comprised of one type of emulsifier, may lead to the development of food products with improved stability to environmental stresses.     

Utilization of Passion Fruit Skin By-Product as Lead(II) Ion Biosorbent

The impact of three commercially available nanoparticles (NPs) on trichloroethylene (TCE) adsorption onto granular activated carbon (GAC) was investigated. TCE adsorption isotherm and column breakthrough experiments were conducted in the presence and absence of silicon dioxide, titanium dioxide, and iron oxide nanoparticles. A rapid small-scale column test (RSSCT) was assessed for its ability to predict TCE adsorption in pilot-scale GAC in the presence and absence of NPs. Zeta potential of the three NPs and the GAC were measured. Particle size distribution of the NP dispersions was analyzed as a function of time. The surface area and the pore size distribution of the virgin and the exhausted GAC were obtained along with transmission electron microscopy and Fourier transform infrared spectroscopy analysis. The effect of NPs was found to be a function of their zeta potential, concentration, and particle size distribution. Due to their electrical charge, NPs attached to the GAC and blocked the pores and thus reduced the access to the internal pore structure. However, due to the fast adsorption kinetics of TCE, no effect from the three NPs was observed in the isotherm and kinetic studies. The RSSCT, on the other hand, accurately predicted the pilot-column TCE breakthrough in the presence of NPs.     

Characterization, antibiofilm, and mechanism of action of novel PEG-stabilized lipid nanoparticles loaded with terpinen-4-ol

Terpinen-4-ol, an active component of tea tree oil, exhibits broad-spectrum antimicrobial activity. However, the high volatilization of terpinen-4-ol and its nonwettability property have limited its application. Our objective was to synthesize novel nanocarriers to deliver and protect terpinen-4-ol. The polyethylene glycol (PEG)-stabilized lipid nanoparticles were prepared and characterized by scanning electron microscope, Zetasizer, and differential scanning calorimetry. These nanoparticles had an average diameter of 397 nm and a Ζ-potential of 10 mV after being modified by glycine. Results showed that homogeneous particle size, high drug loading, stability, and targeting were obtained by the nanoparticles. Liquid chromatography/mass spectrometry showed a sustained release trend from nanoparticles for terpinen-4-ol. Minimum inhibitory concentration and minimum biofilm eradication concentration were tested against Candida albicans ATCC 11231. Studies on isolated mitochondria showed the blockage of biofilm respiration and inhibition of enzyme activity. The effects can be ascribed to localization of terpinen-4-ol on the membrane of mitochondria.     

Components and activity of polysaccharides from coarse tea

Coarse tea contained a high content of polysaccharide complex. Composed of polysaccharide and protein, the polysaccharide complex from tea (TPS) belonged to glycoprotein with the molecular weight () of (10.7-11.0) x 10(4). When mice (7 weeks old, C57BL/8) were injected with TPS, the levels of blood glucose (BG) in normal mice and model mice with high BG were decreased significantly by averages of 13.54 and 22.18%, respectively. The antibody concentration (OD(413 nm)) in the mice injected with 2.4 mg/mL TPS was increased evidently by 44.93% (p < 0.01). TPS treatment was beneficial not only for the subsequent production of interleukin (IL) 2 in spleen cells of adjuvant arthritis (AA) rats but also because it prohibited the body from producing too much IL-1 in AA rats. Treatment of diabetes with coarse tea in both China and Japan may be related to TPS and the content of TPS in coarse tea.     

褐土碳酸钙结核的胶体特性研究

碳酸钙是黄土母质发育土壤的重要胶结物质,对土壤团粒结构的形成具有重要作用。本文采集了碳酸盐褐土中的碳酸钙结核,采用物理分散法和化学分散法分别提取得到褐土碳酸钙结核纳米颗粒和褐土碳酸钙结核胶体,并以工业纳米碳酸钙作为对照对其胶体特性进行研究。采用X射线衍射仪、zeta电位仪和动态光散射仪对褐土碳酸钙结核胶体和工业纳米碳酸钙的矿物组成、zeta电位和胶体稳定性进行了表征。结果表明：褐土碳酸钙结核胶体、褐土碳酸钙结核纳米颗粒和工业纳米碳酸钙的初始颗粒直径分别为224.24、88.01和98.50nm,而褐土碳酸钙结核胶体和褐土碳酸钙结核纳米颗粒的多分散度高于工业纳米碳酸钙。褐土碳酸钙结核胶体中方解石含量为70.3%,其次含有石英、长石和伊利石等矿物;褐土碳酸钙结核纳米颗粒主要含有方解石和伊利石,含量分别为48%和45%。3种碳酸钙胶体表面均带负电荷,其zeta电位绝对值均随着溶液pH的增大而增大。褐土碳酸钙结核胶体在NaCl和CaCl₂溶液中的临界聚沉浓度分别为538.01mmol/L和2.08mmol/L,褐土碳酸钙结核纳米颗粒在NaCl和CaCl₂     

Absorption of 6-O-caffeoylsophorose and its metabolites in Sprague-Dawley rats detected by electrochemical detector-high-performance liquid chromatography and electrospray ionization-time-of-flight-mass spectrometry methods

Absorption and metabolism of a natural compound, 6-O-caffeoylsophorose (CS) from acylated anthocyanins in a red vinegar fermented with purple sweet potato, were clarified. The absorption of CS and conjugated CS in blood from orally administrated Sprague-Dawley rats at a dose of 400 mg/kg was investigated by electrochemical detection-high performance liquid chromatography. As a result, CS was successfully detected in rat plasma (AUC(0-6h), 108.6 ± 8.1 nmol h/mL) and was found to be an intact absorbable polyphenol. In addition, half of the absorbed CS was detected as its conjugates (AUC(0-6h), 50.7 ± 5.7 nmol h/mL) as well as caffeic and ferulic acids from CS. By a time-of-flight-mass spectrometric analysis of CS-administered plasma sample, glucuronide and methylated conjugates of CS were identified, in addition to glucuronide, methylated, or sulfate conjugates of caffeic and ferulic acids. Consequently, CS was absorbed in intact form into rat blood and partly degraded to caffeic and ferulic acids or metabolized by glucuronidation, methylation, or sulfatation.     

Effect of Digestive Enzyme Treatment on Antioxidant Properties of Germinated Green Gram Fortified with Minerals

The antioxidant activity (AA) of green gram germinated in mineral‐fortified water (with iron at 100 or 200 mg/100 mL or zinc at 50 or 100 mg/100 mL), cooked under pressure (PC), or microwaved and subjected to digestive enzyme treatment was determined by using three assay methods. Total AA showed that dehulled grains (DG) had higher AA than whole grains (WG). Cooking reduced the AA in both methods compared with raw grains with a lower percent retention of AA, although significant variations were not found between methods. The percent retention of AA in postdigestion samples was 22.68–51.39 (DG) and 15.67–44.0 (WG). Free radical scavenging activity indicated a different pattern, in which WG exhibited higher AA than DG and, among cooking methods, PC grains had higher activity. A reducing‐power assay showed similar results: DG had lower and PC samples had higher AA. Postdigestion AA of WG was higher for cooked than raw samples, although DG showed the opposite trend. In all cases, samples fortified with iron showed less AA because of prooxidant action of iron. In all assays, postdigestion samples had less activity than predigested extracts. In conclusion, germinated grains showed high AA, influenced by the presence of minerals, dehulling process, and cooking.