离子交换树脂分离碱性溶液中橙皮苷的动力学和热力学

橙皮苷是有着许多生理活性的生物类黄酮。本研究通过静态吸附实验,对D296树脂分离碱性水溶液中高浓度橙皮苷的工艺条件、吸附性能、反应动力学和热力学进行了探讨。结果表明,pH为11.5、浓度为2.43g/L的橙皮苷水溶液适于用小粒径的D296树脂在60℃下浓缩;吸附过程符合Freundish等温吸附式;60℃时树脂与橙皮苷反应的速率常数k为0.5167h-1,且随温度的降低而降低,反应活化能Ea为23.45kJ/mol;在60℃反应平衡时,吸附过程的表观交换反应平衡常数Ke、自由能变化ΔG0、反应热ΔHm0和熵值ΔS0分别为7336.15g2/L2、-24.63kJ/mol,69.69kJ/mol和0.28kJ/mol。因此,交换反应能自发进行,是吸热和熵增加的反应。     

Shorea dasyphylla sawdust for humic acid sorption

The efficacy of Shorea dasyphylla sawdust as an adsorbent for the removal of humic acid from aqueous solution was investigated as a function of pH value, agitation period, agitation rate, initial humic acid concentration and adsorbent dosage. The equilibrium nature of humic acid adsorption was described by the Langmuir, Freundlich and BET isotherms. The experimental adsorption data was best fitted to the Langmuir adsorption model, which gave adsorption capacity of 68.4 mg humic acid adsorbed per gram Shorea dasyphylla sawdust at pH 2.0 and initial humic acid concentration of 80 mg?L^-1. Kinetic studies indicated that the sorption process followed the pseudo-second-order kinetic model. It was revealed that after three cycles of adsorption and desorption, Shorea dasyphylla sawdust retained its promising adsorption ability. With an initial amount of 73.5 mg humic acid adsorbed per gram sawdust, more than 80% of humic acid desorbed by using 0.1 M HCl. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were employed to study the mechanism of the removal of humic acid. From the dimensionless factor, R_L data, it was determined that the adsorption of humic acid onto untreated Shorea dasyphylla sawdust was favourable.     

Antimicrobial Activity of Peptide P34 During Thermal Processing

In the present work, the influence of pH and sodium chloride concentration on thermal stability of antimicrobial peptide P34 was evaluated under different time–temperature conditions by a 2² factorial design experiment. At sterilization conditions (121 °C for 20 min), maximum retention (36%) was obtained at pH between 5.5 and 8.5 and sodium chloride concentration between 0.4 and 0.75 mol/l. For boiling conditions (100 °C for 20 min), antimicrobial activity was about 100% combining pH between 6.0 and 8.0 and salt concentration in the range of 0.65 to 1 mol/l. At low temperature pasteurization conditions (30 min at 65 °C), antimicrobial activity was not affected within the pH range from 5.0 to 8.0. For the three time–temperature conditions tested, the antimicrobial activity was minimal at more acidic or alkaline pH. Sodium chloride concentration of 0.65 mol/l increased thermostability of the peptide P34. Combination of sodium chloride and slight alkaline pH may increase the stability of peptide P34, which is essential to the proper utilization of bacteriocins in food industry.     

巴戟天多糖亲和柱层析纯化的研究

通过静态吸附的方法探讨了巴戟天粗多糖在Con A Sephorose4B亲和填料上静态吸附和脱附情况。结果表明,吸附过程中的pH值和离子强度对平衡吸附量有明显影响,得到的最佳吸附条件是pH7.5,NaCl浓度0.1mol/L;确定的最佳脱附条件为是pH6.5,α-D-甲基葡萄糖苷浓度0.02mol/L。由Langmuir方程对实验数据进行拟合,得到填料的最大吸附量qm为9.58mg/g,表观解离常数Kd为3.43mg/g,巴戟天粗多糖在填料上的吸附速率K为0.144mg/h。在最佳的吸附和洗脱条件下,巴戟天粗多糖被分为MOP-A1和MOP-A2两个组分。     

蔗汁中酚酸类物质气浮分离过程动力学和热力学研究

通过单因素动力学实验和热力学实验研究了气浮法去除甘蔗汁中酚酸类物质的过程。结果表明:在甘蔗汁锤度为15.3°Bx、絮凝剂量1 mg/kg(m絮凝剂/m蔗汁)、p H值8.0、空气流量60 m L/min、磷酸量450 mg/kg(m磷酸/m蔗汁)及气浮时间21 min条件下,蔗汁中酚酸物质气浮去除率可达到53.8%;蔗汁中酚酸类物质气浮分离过程的表观活化能和表观频率因子分别为23.03 k J/mol和1.75×104 min-1。研究结果可为提高低温气浮技术去除富集甘蔗汁中酚酸类物质的效率提供理论和技术依据。     

热改性凹凸棒粘土的吸附热力学和动力学研究

进行了热改性凹凸棒粘土对亚甲基蓝的吸附热力学和动力学性能研究。实验表明：在初始染料质量浓度为50～600mg/L、温度为298～338K时,热改性凹凸棒粘土对亚甲基蓝的吸附符合Langmuir等温吸附方程,△H为1.92 KJ/mol,△G在-25.429～-29.097 KJ/mol之间,△S大于零,此过程为一自发的吸热过程;其吸附动力学数据符合准二级速率方程,吸附表观活化能分别为13.5676 KJ/mol。提出了热改性凹凸棒粘土对亚甲基蓝的吸附过程是由膜扩散和化学吸附共同控制的观点。     

Optimization of Ultrasonic-Assisted Extraction of Polyphenols,Anthocyanins, and Antioxidants from Raspberry (Rubus coreanus Miq.) Using Response Surface Methodology

Ultrasonic-assisted extraction (UAE) was employed for highly efficient extraction of polyphenols, anthocyanins, and antioxidants from raspberry. Process variables were investigated, including ethanol concentration, sonication time, and extraction temperature. A central composite design consisting of three variables and five levels was used to assess the significance of each process variable in UAE applied to raspberry. Analysis of variance confirmed the ethanol concentration as the most significant variable, and reduction of anthocyanins was not observed during UAE. Optimal UAE conditions were an ethanol concentration of 36.2 %, extraction time of 12.84 min, and temperature of 50 °C estimated using overlapped contour plots, which gave predicted maximal values for total polyphenol content (48.67 mg gallic acid equivalent/g), total anthocyanin content (15.23 mg cyanidin-3-glucoside equivalent/g), and antioxidant activity (253 μmol/L trolox equivalent). Verification experiments were carried out under optimal conditions, and good agreement was found between estimated values and experimental values, suggesting that the fitted model was valid and accurate for the UAE process.     

Selection of Process Conditions for High Pressure Pasteurization of Sea Buckthorn Juice Retaining High Antioxidant Activity

Sea buckthorn berries juice is a nutritious beverage, rich in vitamin C and carotenoids with high antioxidant activity. The main requirements for a freshly squeezed sea buckthorn juice production are the cloud stability and antioxidant activity retention after processing. Appropriate process technologies and conditions have to be applied in order to inactivate pectin methyl esterase (PME), responsible for cloud loss, while maintaining the nutritional characteristics and antioxidant activity of the juice. The objectives of the present work were to study and model the effect of thermal treatment and high pressure (HP) processing on the inactivation kinetics of endogenous PME and on total antioxidant activity alteration. Thermal treatment significantly affected PME inactivation and residual antioxidant activity. Processing even at mild process conditions (60 °C for 1 min) resulted in 2.5-fold antioxidant activity reduction and 50 % PME inactivation compared to untreated sample. Pressure and temperature acted synergistically for PME inactivation that followed first-order kinetics with a residual PME activity at all pressure–temperature combinations used (200–600 MPa and 25–35 °C). The effect of temperature and pressure on the inactivation rate constants was expressed through the activation energy and activation volume, respectively. Values of 163 kJ/mol and ?17 mL/mol at reference pressure of 600 MPa and reference temperature of 35 °C were estimated, respectively. Antioxidant activity of the samples was expressed through the determination of the effective concentration (EC₅₀). A slight increase in sea buckthorn antioxidant activity when applying pressures (200–600 MPa) at ambient temperature (25 °C) was observed compared to the corresponding value of untreated juice. Processing at higher temperatures did not significantly alter the total antioxidant activity of sea buckthorn juice. For sample treated at 600 MPa–35 °C for 5 min, a 5 % reduction of total antioxidant activity was observed. These conditions are proposed as effective process conditions for sea buckthorn juice cold pasteurization, based on the higher antioxidant activity retention and simultaneous PME inactivation.     

阴离子交换树脂分离酪蛋白糖巨肽工艺条件优化

采用离子交换树脂从乳清粉中分离酪蛋白糖巨肽(casein glycomacropeptide,CGMP),筛选适于分离CGMP的离子交换树脂并考察静态吸附过程中吸附pH值、吸附时间、缓冲液浓度等因素对CGMP分离效果的影响。乳清粉溶液在pH5.1时离心除杂后与201×4树脂混合,吸附条件为吸附pH3.9、吸附时间1h、缓冲液浓度0.02mol/L、洗脱液为0.5mol/L pH4.0的氯化钠溶液、洗脱时间4h;100g乳清粉利用此工艺条件可得1.45g唾液酸含量10.4%(以蛋白质计)的CGMP。该工艺方法分离过程简单、纯化效果好、唾液酸含量高,适用于工业化生产。     

Macroporous resin purification of grass carp fish (Ctenopharyngodonidella) scale peptides with in vitro angiotensin-I converting enzyme (ACE) inhibitory ability

The adsorption dynamics and thermodynamics of grass carp fish scale peptides (FSPs) onto non-polar macroporous resins (MARs), DA201-C, have been investigated. The adsorption of FSPs was affected by time, pH and peptide concentration. The adsorption process followed the Langmuir adsorption isotherm, and was endothermic (ΔH < 43 kJ/mol). The predominant force in adsorption of FSPs onto DA201-C was hydrophobic. Depending on this force, the dynamic adsorption and gradient desorption results showed that DA201-C resins were good at desalting and enriching peptides with higher contents of hydrophobic amino acids, and these peptides had higher ACE inhibitory capabilities in vitro. The lowest concentration at which the eluted fraction possessed half of its original ACE activity (IC₅₀) was 0.13 mg/ml. The results indicated that fish scale peptides produced showed good ACE-inhibitory effect in vitro and fish scales are a good source of peptides with in vitro ACE inhibitory activity.     

Heat-treated wood as chromium adsorption material

Heavy metals adsorption with lignocellulosic materials has been heavily researched in the last years. Since heat activation has been used with good results to increase the adsorption capacity of some materials, heat-treated wood might be a better adsorbent. This hypothesis is the basis of the present study. The adsorption tests were made with powdered pine wood, heat-treated at 190–210?°C. All the heat-treated samples showed a significantly higher adsorption compared to untreated wood. The maximum adsorption was obtained at pH 3 for heat-treated wood at 210?°C. The kinetics of the adsorption process fitted a pseudo-second-order reaction (R² 0.990–0.996). Adsorption fitted well both the Langmuir and the Freundlich model, but the Freundlich model presented higher R² (0.988–0.998). The q_max values estimated by the Langmuir plotting were in the range 15.6–19.4 mg/g and the n values from Freundlich isotherms between 1.87 and 2.39. Heat-treated wood was a better adsorption material than untreated wood for chromium adsorption. This can be a good application for the sawdust produced by the processing of heat-treated wood at primary and secondary wood processing mills or for the recycling of heat-treated wood at the end of product life.     

Square Wave Voltammetric Determination of Fomesafen Herbicide Using Modified Nanostructure Carbon Paste Electrode as a Sensor and Application to Food Samples

Cyclic and square wave voltammetric measurements were performed to deduce the electrochemical behavior of fomesafen herbicide on the prepared carbon nanotube paste electrodes. Fomesafen has created a well-defined cathodic peak at ?540 mV (vs. Ag/AgCl), but no corresponding oxidation peak has appeared on the reverse scan. The influence of the pH on the electro-reduction peak was tested at various pH values, and the E _p versus pH plot suggested that protons are involved in reduction process. Electrochemical studies showed that –NO₂ group was responsible for the reduction process. A linear relationship has been constructed in the concentration range of 0.30–40 mg/L. The limits of detection and quantification values were obtained as 0.089 and 0.297 mg/L, respectively. Fomesafen was determined in the presence of some well-known pesticides, and the extent of recoveries of 5 mg/L fomesafen in the presence of equal amounts of pesticides anilazine, pymetrozine, and triflumizole was 103.7 ± 0.9, 94.3 ± 0.4, and 97.9 ± 0.5 %, respectively (n = 3). The accuracy of the recommended method was further proved by the determination of fomesafen in spiked real samples such as apricot juice, cherry juice, and lake water with a relative error of ?4.2, ?2.8, and ?1.8 %, respectively. The obtained results suggest that the recommended method is sufficiently accurate, selective, and precise.     

一种球形木质素吸附剂吸附L-天门冬氨酸的性能研究

以硫酸盐木质素为原料,利用反相悬浮技术制备出球形木质素吸附剂。利用球形木质素吸附剂吸附L-天门冬氨酸,并进行吸附条件的优选实验。结果表明,吸附效果取决于吸附时间、吸附质初始质量浓度、吸附质溶液pH值以及盐浓度等。当吸附时间150 min、吸附质初始质量浓度2000 mg/L、吸附质溶液pH值为3时,球形木质素吸附剂的平衡吸附容量可达518 mg/g,最大饱和吸附量达到625 mg/g。此外,无机盐氯化铵对球形木质素吸附剂吸附率的影响大于氯化钠,而且随着盐浓度的增大,吸附率从85.6%降至21.4%。同时进行了解吸再生和对比实验,发现用0.6 mol/L的氨水解吸时,解吸率可达99.3%,且再生后的木质素吸附剂仍具有很好的吸附性能。     

沸石改性聚丙烯酰胺复合材料对诱惑红色素的吸附研究

本实验采用一锅法合成了沸石改性聚丙烯酰胺复合材料,并将其作为吸附剂,结合紫外-可见吸收光谱法,研究了其对诱惑红色素的吸附性能。探讨了溶液pH和振荡时间对吸附过程的影响,研究了吸附动力学、吸附等温线和吸附热力学,并对该复合材料进行了再生性能考察。结果表明:在溶液pH为6,诱惑红色素在振荡时间为80 min之内可达到吸附平衡,吸附过程符合拟二级动力学模型(R²=0.9984)和Langmuir等温吸附模型;当温度为20 ℃时,ΔG=(4.23 kJ/mol,ΔH=39.01 kJ/mol,ΔS=145.22 J/mol/K;吸附剂在再生使用3次内吸附性稳定。由此可知,沸石改性聚丙烯酰胺复合材料对吸附诱惑红色素具有良好的吸附性和再生性。     

Thermal Chlorophyll Degradation Kinetics of Mint Leaves Puree

Thermal degradation kinetics of chlorophyll ‘a’, ‘b’ and total chlorophyll in mint leaves puree were investigated as function of pH (4.5–8.5) and processing temperature (80–145°C), respectively. Mint puree was processed at 80°to 100°C at pH 4.5, while that at pH 5.5 to 8.5 was processed at 105°to 145°C. Chlorophyll degradation followed the first order reaction kinetics. Good agreement was found between estimated and experimental chlorophyll retention in all cases (R² > 0.86; MRQE < 0.27). Activation energies ranged from 6.45 to 47.67 kJ/mol. Reaction rate and activation energy data indicated that chlorophylls were more stable at alkaline pH. Transition state theory was applied to estimate the enthalpy, entropy and Gibbs free energy of activation. Enthalpy (ΔH^#) ranged from 3.14 to 44.66 kJ/mol, while entropy (ΔS^#) ranged from ?0.157 to ?0.266 kJ/(mol K). The overall free energy change was 105.76 kJ/mol. Results indicated that, the compensation effect did not exist for chlorophyll degradation in mint puree during thermal processing.     

大豆荚甾醇提取动力学与热力学的研究

研究了用乙醇溶液从大豆荚中提取甾醇。通过预实验,选定合适的提取条件,测定了提取液中甾醇质量浓度随提取温度和提取时间的变化;将获得的实验数据进行了模型拟合;计算了动力学参数和热力学参数。结果表明：高的提取温度可获得快的提取速度和高的平衡质量浓度;提取过程符合一级平板动力学模型;研究条件下提取过程的表观活化能为22.47 kJ/mol;内扩散系数在1.04×10_^-10 m_²/min到2.45×10_^-10 m_²/min的范围内随提取温度升高而增大;半衰期随提取温度升高而从17.3 min降至4.1 min;吉布斯自由能均小于零,表明甾醇提取过程为自发过程;提取过程焓变为35.16 kJ/mol、熵变为125.8 J/(mol.K),过程吸热、熵增。所得结果可为业界提供参考。     

Laboratory-scale extraction and characterization of ice-binding sericin peptides

Sericin peptides (SPs) are a new cryoprotectant with protecting abilities for organisms or biomacromolecule in food stuff from freezing injury in subzero environments. The extraction of ice-binding sericin peptides (I-SPs) by ice affinity extraction adsorption and their cryoprotective effect on Lactobacillus Delbrueckii Subsp. bulgaricus LB340 LYO during frozen storage was studied in this paper. The optimal extraction conditions by application of a new and assembled ice absorption apparatus were identified as temperature of ?3 °C, SPs concentration of 5 mg/mL, and extraction time of 3 h. Compared with SPs, I-SPs were found to be increased in the contents of some special amino acid residues, including Ser, Thr, Gly, and Ala, which might be relative with the ice affinity as well as the cryoprotective activity of ice-structuring proteins. Meanwhile, the molecular mass distribution data implied that the free amino acids in the SPs could be excluded from the ice affinity adsorption, and peptides containing 3–6 amino acid residues might be more liable to adsorb to ice surface. Furthermore, with addition of I-SPs at concentrations of more than 0.01 mg/mL, LB340 strain had a higher survival rate after frozen storage compared to the water control as well as SPs (p < 0.05).     

Potentiometric Determination of Aluminum in Foods, Pharmaceuticals, and Alloys by AlMCM-41-Modified Carbon Paste Electrode

A new chemically modified electrode is constructed by incorporating AlMCM-41 into carbon paste matrix (AlMCM-41-MCPE) and used as a sensitive sensor for detection of aluminum in aqueous and nonaqueous solutions. The rapid exchange kinetics in the membrane results in a near-Nernstian behavior of the modified electrode and makes it a suitable potentiometric sensor for detection of aluminum. A linear response in concentration range from 1.0?×?10^?6 to 1.0?×?10^?1 mol/L (0.027 μg/mL–2.7 mg/mL) was obtained with a detection limit of 4.6?×?10^?7 mol/L for the potentiometric detection of aluminum. Selectivity coefficients of a number of interfering cations have been estimated. The interference from many of the investigated ions is negligible. The AlMCM-41-MCPE is suitable for use in aqueous solution of pH 2–6 and in partially nonaqueous medium. The modified electrode exhibited a fast response time (~8 s), good stability, and an extended lifetime. The developed sensor was used successfully for the determination of Al³⁺ in some alloys, drugs, and food products.     

Application of a New Functionalized Nanoporous Silica for Simultaneous Trace Separation and Determination of Cd(II), Cu(II), Ni(II), and Pb(II) in Food and Agricultural Products

A novel sorbent for simultaneous separation of cadmium, copper, nickel, and lead was prepared by functionalizing SBA-15 nanoporous silica with dithizone. A solid-phase extraction method using the above sorbent was developed to separate and preconcentrate trace amounts of cadmium, copper, nickel, and lead ions from food and agricultural products by flame atomic absorption spectrometry measurements. The optimum experimental conditions such as pH; flow rates; type, concentration, and volume of the eluent; breakthrough volume; and effect of coexisting ions on the separation and determination of these heavy metals were evaluated. The extraction efficiencies for the mentioned heavy metals were greater than 97 %, and the limits of detection were 0.09, 0.16, 0.21, and 0.45 μg?L^?1 for cadmium, copper, nickel, and lead, respectively. The preconcentration factor for simultaneous analysis of the four heavy metals was found to be 100 approximately. The relative standard deviations of the method were <5 % for 10 separate column experiments for the determination of 5.0 μg of cadmium, copper, nickel, and lead ions. The adsorption capacity of the dithizone-SBA-15 was 189 mg?g^?1 for cadmium, 102 mg?g^?1 for copper, 91 mg?g^?1 for nickel, and 208 mg?g^?1 for lead.     

蚕丝纤维吸附辛基酚聚氧乙烯醚的动力学研究

为实现蚕丝产品中烷基酚聚氧乙烯醚( APEO)的高效监控检测,研究蚕丝纤维对辛基酚聚氧乙烯醚(OPEO)的吸附特性.结果表明,OPEO在蚕丝纤维上的吸附符合Langmuir模型,吸附动力学符合拟二级动力学模型,并且初始浓度越大,平衡速率常数越小,到达平衡的时间越长.OPEO溶液的温度越高,平衡速率常数越大.毛孔内扩散是...