新型卵磷脂/非离子表面活性剂混合胶束的制备研究

目的:研制一种新型卵磷脂/非离子表面活性剂的混合胶束体系。方法:采用直接分散法,选取了三大类的非离子表面活性剂（吐温系列,聚甘油脂肪酸单酯系列以及蔗糖单脂肪酸酯系列）对卵磷脂进行增溶比较,并进行复配研究,以透光率、粒径大小及粒度分布作为体系的评价指标。结果:表面活性剂的脂肪酸链长越短对卵磷脂增溶越显著,十聚甘油单月桂酸酯（L-7D）对卵磷脂（PC）的增溶效果好,以L-7D制备的卵磷脂混合胶束的平均粒径为10～15nm,PDI值在0.1～0.3之间,表现出良好的粒径均一性。结论:十聚甘油单月桂酸酯对卵磷脂的增溶效果显著,形成的混合胶束体系透光率高,粒径小且粒径分布集中,可尝试作为非肠道给药的新型载体。      

混合表面活性剂胶束增效测定奶粉中的亚硝酸盐

样品去除蛋白质及脂肪后,亚硝酸盐与对氨基苯磺酸重氮化,再与盐酸萘乙二胺偶合形成红色偶氮染料,反应体系中加入TritonX-100与OP混合溶液后,吸光度增强,建立了测定微量亚硝酸盐的新方法。该方法的最大吸收波长为510nm,检出限为0.lmg/kg,线性范围为0.2mg/L-2.5mg/L,用于奶粉中微量NO2-的测定,结果满意。     

阴离子/非离子表面活性剂复配体系的紫外可见光谱

运用760CRT双光束紫外可见分光光度计对阴离子/非离子表面活性剂（AES/FC8P）复配体系的吸收光谱进行了较详细的研究.结果显示,随着浓度的变化,出现可见光区460 nm处吸收峰消失和近紫外区吸收峰转移（350 nm→380 nm）的现象;出现这两种现象时所对应的表面活性剂浓度分别位于复配表面活性剂的临界胶束浓度附近.     

织物在非离子表面活性剂反胶束体系中同浴染色及酶处理

主要研究了羊毛织物在非离子表面活性剂反胶束体系中的同浴染色及酶处理。所用表面活性剂为聚氧乙烯山梨醇油酸酯（吐温-85）。酶在吐温-85反胶束体系中的溶解性通过小角X-射线散射分析法测定。测定结果表明，吐温-85反胶束体系可以将染料和酶同时置于该反胶束体系内部而不会改变染料和酶的结构。在该反胶束体系中，羊毛织物对酸性染料和活性染料可有效吸附。不同的酶在该体系中的反应活性不同，染料对酶有负面作用。     

改性卵磷脂作为生物表面活性剂对胆固醇的微乳化研究

对大豆卵磷脂进行羟氯化改性,以此为表面活性剂、乙醇为助表面活性剂,对胆固醇进行微乳化实验。采用三相图形式和电导率对微乳化体系进行跟踪检测。改性大豆卵磷脂与未改性大豆卵磷脂比较,在水中的分散性、微乳化性能明显提高,因此羟氯化改性卵磷脂可作为制备药物载体。     

高纯卵磷脂的制备研究

概述了近些年来有关制备高纯卵磷脂的研究成果和进展,对五种制备高纯卵磷脂的方法进行了简要的介绍和评述。     

超滤法测定表面活性剂临界胶束浓度

对超滤法测定表面活性剂的临界胶束浓度(CMC)的单点式超滤法、超滤曲线法、双点式超滤法进行了研究,比较了理想与真实超滤曲线,对超滤膜用于超滤法测定CMC的适用性及容积效应进行了考察.初步探讨了用双点式超滤法代替作超滤曲线法测定CMC的可行性和准确性,并与单点式超滤法进行了比较.试验结果表明,用双点式超滤法测定CMC具有准确性较高、操作简便、节省时间和节约样品用量等优点.用双点法测得的SDS和SLAS的CMC分别为6.70mmol/L和1.40mmol/L;与超滤曲线法得到的CMC相比,偏差分别为2.9%和3.4%.     

Gemini型阳离子表面活性剂反胶束体系萃取纤维素酶的研究

本文研究了Gemini型阳离子酯季铵盐表面活性剂Ⅱ-14-3反胶束萃取纤维素酶的性能,以探索新型表面活性剂在反胶束萃取酶蛋白中的应用。考察了水相pH、离子强度、离子种类、酶浓度、表面活性剂浓度、助溶剂浓度、溶剂比和助表面活性剂(卵磷脂)等因素对萃取率的影响,确定了萃取纤维素酶的最佳条件:[NaCl]=50mmol/L,[Ⅱ-14-3]=0.3mmol/L,pH6.4,C0=0.14,溶剂比S=1.0,萃取率E接近80%,其酶活达到原来的93.38%;若加入适量的卵磷脂([Ⅱ-14-3]/[PC]=36:1)可提高萃取率,萃取率E达90%以上,且酶活达到121.41%。并且从反胶束微观结构给予解释。     

木质素液化产物制备非离子表面活性剂的研究

以碱木质素(AL)为原料,通过催化液化处理提取木质素酚类产物(LAL),利用催化液化产物富含的酚羟基与环氧氯丙烷(ECH)在碱性条件下反应生成水不溶的木质素醚类中间体,该中间体的环氧基可与乙二醇或者聚乙二醇PEG顶端的羟基发生缩合反应,生成木质素聚醚的非离子表面活性剂(NLAL)。利用红外光谱分析仪、紫外分光光度计等对LAL的性能进行分析,发现与AL相比,LAL酚羟基含量增加,分子量降低,大大提升了反应活性,有利于下一步改性反应的进行。采用红外光谱分析仪、表面张力测定仪、泡沫分析仪等对NLAL各方面性能进行表征。结果表明:NLAL对应临界胶束浓度的表面张力即最低表面张力为37.71m N/m,具有非常好的水溶性和润湿性能,属于低泡类的表面活性剂,做乳化剂可形成O/W型乳液,乳化性能较为优良。     

蛋黄卵磷脂的制备研究

研究了鸡蛋卵黄卵磷脂的制备工艺和产品质量分析。结果表明,使用95%乙醇分三次提取粗卵磷脂效果最佳,可制得卵磷脂含量约为70%的粗卵磷脂,得率约为10%;进一步使用ZnCl2沉淀制备卵磷脂效果最佳,使用10% ZnCl2纯化粗卵磷脂的回收率约为80%,产品中卵磷脂含量达94.25%;薄层层析结果表明,卵磷脂产品只有两个明显的斑点,分别为PC及PE两种成分。分光光度法测得卵磷脂的紫外最大吸收峰在215nm波长处。     

Effect of solvent and temperature on the size distribution of casein micelles measured by dynamic light scattering

The objectives of this study were to investigate the effect of the solvent on the accuracy of casein micelle particle size determination by dynamic light scattering (DLS) at different temperatures and to establish a clear protocol for these measurements. Dynamic light scattering analyses were performed at 6, 20, and 50°C using a 90Plus Nanoparticle Size Analyzer (Brookhaven Instruments, Holtsville, NY). Raw and pasteurized skim milk were used as sources of casein micelles. Simulated milk ultrafiltrate, ultrafiltered water, and permeate obtained by ultrafiltration of skim milk using a 10-kDa cutoff membrane were used as solvents. The pH, ionic concentration, refractive index, and viscosity of all solvents were determined. The solvents were evaluated by DLS to ensure that they did not have a significant influence on the results of the particle size measurements. Experimental protocols were developed for accurate measurement of particle sizes in all solvents and experimental conditions. All measurements had good reproducibility, with coefficients of variation below 5%. Both the solvent and the temperature had a significant effect on the measured effective diameter of the casein micelles. When ultrafiltered permeate was used as a solvent, the particle size and polydispersity of casein micelles decreased as temperature increased. The effective diameter of casein micelles from raw skim milk diluted with ultrafiltered permeate was 176.4 ± 5.3 nm at 6°C, 177.4 ± 1.9 nm at 20°C, and 137.3 ± 2.7 nm at 50°C. This trend was justified by the increased strength of hydrophobic bonds with increasing temperature. Overall, the results of this study suggest that the most suitable solvent for the DLS analyses of casein micelles was casein-depleted ultrafiltered permeate. Dilution with water led to micelle dissociation, which significantly affected the DLS measurements, especially at 6 and 20°C. Simulated milk ultrafiltrate seemed to give accurate results only at 20°C. Results obtained in simulated milk ultrafiltrate at 6°C could not be explained based on the known effects of temperature on the casein micelle, whereas at 50°C, precipitation of amorphous calcium phosphate affected the DLS measurement.     

Preparation and characterization of catalase-loaded solid lipid nanoparticles based on soybean phosphatidylcholine

BACKGROUND: High‐purity soybean phosphatidylcholine (SPC) (94%) were prepared using macroporous resin adsorption chromatography previously. Catalase is a food enzyme for promoting health and protecting against many age‐related disease. Solid lipid nanoparticles (SLN) are safe immobilizing systems for efficient protein transportation to biomembranes while avoiding adverse degradation of protein. This study was aimed at developing and characterizing catalase‐loaded SLN using SPC as solubilizers and stabilizing agents, to protect catalase from proteolysis. RESULTS: Catalase‐loaded SLN were prepared by the double emulsification method and solvent evaporation techniques, using acetone–methylene chloride (1:1, v/v) as an organic solvent, SPC–tripalmitin as oil phase and Poloxamer 188 as a surfactant. The optimized SLN were prepared using an SPC:tripalmitin ratio of 5% (w/w), 20 s plus 30 s sonication, 20 g L^?1 Poloxamer 188 and 1:2 (v/v) of oily phase:outer aqueous phase ratio. The mean particle size of SLN was 296.0 ± 7.0 nm, polydispersity index range and zeta potential were 0.322–0.354 and ? 36.4 ± 0.6, respectively, and encapsulation efficiency reached its maximum of 77.9 ± 1.56%. Catalase, which was found to distribute between the solid lipid and inner aqueous phase, was gradually released from SLN up to 20% within 20 h. Catalase‐loaded SLN had stably retained 30% of H₂O₂‐degrading activity for at least 24 h in a proteolytic environment, while free catalase lost its activity within 1 h. CONCLUSION: Catalase can indeed be loaded in tripalmitin‐based SLN using SPC as solubilizers and stabilizing agents, which protected it against proteolysis, suggesting the potential application of SPC in delivery and protection of functional food enzyme. Copyright © 2011 Society of Chemical Industry     

The effect of ultrasound on casein micelle integrity

Samples of fresh skim milk, reconstituted micellar casein, and casein powder were sonicated at 20 kHz to investigate the effect of ultrasonication. For fresh skim milk, the average size of the remaining fat globules was reduced by approximately 10 nm after 60 min of sonication; however, the size of the casein micelles was determined to be unchanged. A small increase in soluble whey protein and a corresponding decrease in viscosity also occurred within the first few minutes of sonication, which could be attributed to the breakup of casein-whey protein aggregates. No measurable changes in free casein content could be detected in ultracentrifuged skim milk samples sonicated for up to 60 min. A small, temporary decrease in pH resulted from sonication; however, no measurable change in soluble calcium concentration was observed. Therefore, casein micelles in fresh skim milk were stable during the exposure to ultrasonication. Similar results were obtained for reconstituted micellar casein, whereas larger viscosity changes were observed as whey protein content was increased. Controlled application of ultrasound can be usefully applied to reverse process-induced protein aggregation without affecting the native state of casein micelles.     

The association of lipophilic phospholipids with native bovine casein micelles in skim milk: Effect of lactation stage and casein micelle size

A known biological role of casein micelles is to transport calcium from mother to young and provide amino acids for growth and development. Previous reports demonstrated that modified casein micelles can be used to transport and deliver hydrophobic probes. In this study, the distribution of lipid-soluble phospholipids, including sphingomyelins (SM) and phosphatidylcholines (PC), was quantified in whole raw milk, skim raw milk, and casein micelles of various sizes during early, mid, and late lactation stages. Low-pressure size exclusion chromatography was used to separate casein micelles by size, followed by hydrophobic extraction and liquid chromatography–mass spectrometry for the quantification of PC and SM. Results showed that the SM d18:1/23:0, d18:1/22:0, d18:1/16:0, d16:1/22:0, d16:1/23:0, and d18:1/24:0 and the PC 16:0/18:1, 18:0/18:2, and 16:0/16:0 were dominating candidates appearing in maximum concentration in whole raw milk obtained from late lactation, with 21 to 50% of total SM and 16 to 35% of total PC appearing in skim milk. Of the total SM and PC found in skim milk, 35 to 46% of SM and 22 to 29% of PC were associated with the casein micelle fraction. The highest concentrations of SM d18:1/22:0 (341 ± 17 µg/g of casein protein) and PC 16:0/18:1 (180 ± 20 µg/g of casein protein) were found to be associated with the largest casein micelles (diameter = 149 nm) isolated in milk from late lactation, followed by a decrease in concentration as the casein micelle size decreased.     

Importance of casein micelle size and milk composition for milk gelation

The economic output of the dairy industry is to a great extent dependent on the processing of milk into other milk-based products such as cheese. The yield and quality of cheese are dependent on both the composition and technological properties of milk. The objective of this study was to evaluate the importance and effects of casein (CN) micelle size and milk composition on milk gelation characteristics in order to evaluate the possibilities for enhancing gelation properties through breeding. Milk was collected on 4 sampling occasions at the farm level in winter and summer from dairy cows with high genetic merit, classified as elite dairy cows, of the Swedish Red and Swedish Holstein breeds. Comparisons were made with milk from a Swedish Red herd, a Swedish Holstein herd, and a Swedish dairy processor. Properties of CN micelles, such as their native and rennet-induced CN micelle size and their ζ-potential, were analyzed by photon correlation spectroscopy, and rennet-induced gelation characteristics, including gel strength, gelation time, and frequency sweeps, were determined. Milk parameters of the protein, lipid, and carbohydrate profiles as well as minerals were used to obtain correlations with native CN micelle size and gelation characteristics. Milk pH and protein, CN, and lactose contents were found to affect milk gelation. Smaller native CN micelles were shown to form stronger gels when poorly coagulating milk was excluded from the correlation analysis. In addition, milk pH correlated positively, whereas Mg and K correlated negatively with native CN micellar size. The milk from the elite dairy cows was shown to have good gelation characteristics. Furthermore, genetic progress in relation to CN micelle size was found for these cows as a correlated response to selection for the Swedish breeding objective if optimizing for milk gelation characteristics. The results indicate that selection for smaller native CN micelles and lower milk pH through breeding would enhance gelation properties and may thus improve the initial step in the processing of cheese.     

甘蔗混合汁粒径分布及陶瓷微滤膜过滤阻力研究

建立了甘蔗混合汁中颗粒粒径分布测定和分析方法;研究了0．1μm、0．2μm和0．45μm陶瓷微滤膜分析甘蔗混合汁时的阻力分布,探讨了不同膜元件主要阻力形式,确定了阻力分析方法。结果表明：致密性膜的制造精度越高,过滤料液时总阻力相对较小,孔隙率高的膜元件堵塞阻力随膜孔径减小而降低,利于膜通量的恢复和延长使用时间。     

Span40在非离子反胶束体系中对直接黄棕ND3G染色棉织物的影响

为了提高阴离子染料在反胶束体系中对棉织物的染色性能,本文在非离子Triton X-100反胶束体系中加入Span40制备出非离子混合反胶束体系,并以其为介质使用直接黄棕3G对棉织物进行染色,重点研究Span40对反胶束体系的饱和增溶水量、水池直径、聚集密度和电导率等结构特征以及直接染料对棉织物染色性能的影响。结果表明,当Span40含量为50%时反胶束体系的饱和增溶水量呈现最大值,反胶束体系的水池直径和聚集密度随着Span40的增加而增大,导致反胶束体系电导率降低,减小了直接染料与棉织物的静电排斥作用及其与表面活性剂对棉织物的竞争吸附作用,从而使直接黄棕3G对棉织物的吸附和染色性能得以提高。     

Association of total mixed ration particle fractions retained on the Penn State Particle Separator with milk,fat, and protein yield lactation curves at the cow level

As part of a larger project aiming to develop management evaluation tools based on results from test-day (TD) models, the objective of this study was to examine the effect of physical composition of total mixed rations (TMR) tested quarterly from March 2006 through December 2008 on milk, fat, and protein yield curves for 25 herds in Ragusa, Sicily. A random regression sire-maternal grandsire model was used to estimate variance components for milk, fat, and protein yields fitted on a full data set, including 241,153 TD records from 9,809 animals in 42 herds recorded from 1995 through 2008. The model included parity, age at calving, year at calving, and stage of pregnancy as fixed effects. Random effects were herd × test date, sire and maternal grandsire additive genetic effect, and permanent environmental effect modeled using third-order Legendre polynomials. Model fitting was carried out using ASREML. Afterward, for the 25 herds involved in the study, 9 particle size classes were defined based on the proportions of TMR particles on the top (19-mm) and middle (8-mm) screen of the Penn State Particle Separator. Subsequently, the model with estimated variance components was used to examine the influence of TMR particle size class on milk, fat, and protein yield curves. An interaction was included with the particle size class and days in milk. The effect of the TMR particle size class was modeled using a ninth-order Legendre polynomial. Lactation curves were predicted from the model while controlling for TMR chemical composition (crude protein content of 15.5%, neutral detergent fiber of 40.7%, and starch of 19.7% for all classes), to have pure estimates of particle distribution not confounded by nutrient content of TMR. We found little effect of class of particle proportions on milk yield and fat yield curves. Protein yield was greater for sieve classes with 10.4 to 17.4% of TMR particles retained on the top (19-mm) sieve. Optimal distributions different from those recommended may reflect regional differences based on climate and types and quality of forages fed.     

A possible structure of the casein micelle based on high-resolution field-emission scanning electron microscopy

New electron micrographs, produced using the technique of Field Emission Scanning Electron Microscopy, showing the details of the micellar surface, are presented. The images show the micellar surfaces without any coating, and suggest that the surface of the micelle may have a much more complex structure than has previously been demonstrated. Although there appear to be no spherical subunits (submicelles), there is evidence for the organization of the caseins into tubular structures within the micelle. The surface is not smooth, and contains gaps between the substructures. The observations are discussed in terms of published models of micellar structure, where is it suggested how the depiction of the micellar surface can be used to explain certain factors of its reactivity and behaviour.     

Influence of heat treatment of goat milk on casein micelle size,rheological and textural properties of acid gels and set type yoghurts

Acid gels and yoghurts were made from goat milk that was heated at 72°C/30 s, 85°C/5 min, and 95°C/5 min, followed by acidification with starter culture at 43C until pH 4.6. The rheological and textural properties of acid gels and yoghurts were analyzed using dynamic low amplitude oscillatory rheology and back extrusion texture analysis, respectively. The effect of goat milk heat treatment on the mean casein micelle diameter and protein profile was also determined by dynamic light scattering and SDS PAGE electrophoresis, respectively. The shortest gelation and fermentation time was recorded for yoghurt prepared from milk heated at 85°C/5 min. Also, the pH of gelation, the storage moduli (G′) and yield stress were higher for this yoghurt, compared with the other two. Textural properties of goat milk yoghurts such as firmness and consistency were strongly affected by milk heat treatment, and the highest values were recorded for yoghurt produced from milk preheated at 85°C/5 min, as well. The largest casein micelles were measured after 85°C/5 min treatment and their size decreased at higher temperature, despite higher denaturation of whey proteins at the most intense heat regime, indicating the structure changes that influence on the acid gelation.