魔芋膳食纤维对油脂体外消化特性的影响

向油脂乳液中加入一定量魔芋膳食纤维，采用pH-stat法模拟油脂体外消化过程，考察魔芋膳食纤维对乳液在胃肠道中消化特性的影响，并研究乳液消化前后有效粒径、粒径分布、Zeta电位和微观结构的变化。结果表明，魔芋膳食纤维对乳液消化特性和消化前后理化性质产生显著性影响。随着纤维含量增加，乳液初始消化速率和最终消化程度均减小，含0.5%(质量分数)魔芋膳食纤维的乳液经胰脂肪酶消化120 min后脂肪酸释放率仅为14.84%;乳液粒径在体外消化的不同阶段逐渐增大，且同一消化阶段随纤维添加量增加而增大；肠消化后Zeta电位绝对值均大于40 mV,脂滴不稳定，发生聚集。脂肪乳液中脂质的最终消化率随体系中纤维添加量的增加而降低，该研究结果对胃肠道中脂质消化的控制及低热量功能食品的开发具有重要意义。     

柚皮苷纳米乳液递送体系的消化特性

通过体外模拟消化研究以乳清分离蛋白(whey protein isolate,WPI)、ι-卡拉胶(ι-carrageenan,ι-Car)和阿拉伯胶(gum arabic,GA)作为乳化剂稳定的单层以及双层柚皮苷(naringin,NA)纳米乳液的消化规律。对NA单层纳米乳液(NA/WPI-e)和NA双层纳米乳液(NA/WPI/ι-Car-e和NA/WPI/GA-e)进行液滴粒径、Zeta电位和微观结构检测,考察其在胃肠消化阶段的水解程度。结果表明:在胃模拟消化中,单层及双层纳米乳液的液滴聚集,乳液平均粒径显著增大(P0.05),Zeta电位绝对值基本上高于原始乳液;在小肠模拟消化过程中,NA纳米乳液均发生解絮凝现象。经胃肠消化后NA/WPI-e的游离脂肪酸(free fatty acids,FFAs)释放率最高为97.3%,NA生物利用率为10.06%。NA/WPI/ι-Car-e的FFAs释放率和NA生物利用率均低于NA/WPI-e,而GA质量浓度为1 mg/mL的NA/WPI/GA-e则表现出比NA/WPI-e更高的生物利用率,达到12.13%。NA/WPI-e、NA/WPI/ι-Car-e、NA/WPI/GA-e的FFAs释放率均显著高于对照组(34%),表明纳米乳液递送体系能有效提高NA的生物利用率。     

不同大分子乳化剂构建番茄红素纳米乳液的体外消化规律比较

通过体外模拟消化,研究以辛烯基琥珀酸酯化（octenyl succinic anhydride,OSA）变性淀粉、乳清分离蛋白（whey protein isolate,WPI）、酪蛋白酸钠（sodium caseinate,SC）为乳化剂构建的番茄红素纳米乳液的消化规律。结果表明,消化过程中纳米乳液的液滴大小、Zeta电位和微观结构取决于乳化剂类型,OSA变性淀粉和蛋白质类乳化剂构建的纳米乳液分别在肠和胃阶段发生水解,液滴聚集,乳液平均粒径增大,同时Zeta电位绝对值达到最小。经胃肠消化后3 种乳化剂构建的番茄红素纳米乳液游离脂肪酸释放率的大小排序为OSA变性淀粉（92.25%）＞SC（86.53%）＞WPI（79.88%）,高于对照组的48.7%,表明纳米乳液包埋体系能有效改善番茄红素的消化特性,且以OSA变性淀粉构建的纳米乳液表现出比蛋白质类乳化剂更高的番茄红素生物利用率,达到（25.60±3.08）%。     

玉米醇溶蛋白纳米颗粒的体外消化特性

为了研究基于天然生物大分子的纳米递送体系在消化过程中物理化学性质的变化,本研究以姜黄素(Curcumin)为芯材,玉米醇溶蛋白(Zein)为壁材,通过反溶剂沉淀法制备了包埋姜黄素的玉米醇溶蛋白纳米颗粒(CZNPs),通过光谱学方法和电子显微镜对CZNPs的物化性质进行了表征,并在体外模拟消化模型中对CZNPs的消化特性进行了研究。结果表明,当姜黄素与Zein的质量比为1:40时,姜黄素的包埋率最高,为99%±1%,制得的CZNPs为球形纳米颗粒,平均粒径为118.6±0.7 nm、Zeta电位为19.9±3.79 mV,且颗粒之间出现轻微粘连。在体外模拟胃消化过程中,随着消化时间的延长,CZNPs出现明显聚集,其平均粒径增至8000 nm;且部分Zein发生降解,生成小分子量的氨基酸,同时缓慢释放出姜黄素。在后续的模拟肠消化过程中,CZNPs的聚集程度随着消化时间的延长而明显减弱,但Zein没有继续降解,姜黄素的释放也没有明显增大。因此,玉米醇溶蛋白纳米颗粒是一种比较有效的口服递送体系,可能应用于功能性食品和口服药物的开发中。     

基于OSA变性淀粉为乳化剂的番茄红素纳米乳的体外消化特性研究

以2种不同的辛烯基琥珀酸酯变性淀粉(OSA1、OSA2变性淀粉)作为乳化剂,构建番茄红素稳定的纳米乳液体系,通过体外模拟消化,研究其消化特性。结果表明:2种纳米乳液的粒径在口腔、胃消化阶段并无明显变化,在肠消化阶段明显增加;结合激光共聚焦显微镜观察可知,2种OSA变性淀粉为乳化剂的纳米乳都在模拟口腔和胃阶段变化较小,在模拟肠消化阶段中会发生大量水解。2种纳米乳液中游离脂肪酸释放总量OSA2 OSA1,且2种纳米乳液的番茄红素生物可给率也均远高于对照组,番茄红素纳米乳液的生物可给率OSA2 OSA1。     

包覆花色苷W_1/O/W_2型乳液的消化特性及其缓释效果

研究体外消化对包埋葡萄皮花色苷(anthocyanins,ACNs)W_1/O/W_2型乳液控释和抗氧化性能的影响。W_1/O/W_2型乳液粒径约为(149.33±1.44)nm,并且呈双峰分布,ACNs的包封率为(82.99±2.38)%。体外口腔消化对W_1/O/W_2型乳液液滴结构无明显影响。经口进入模拟胃消化后,W_1/O/W_2型乳液因蛋白质水解失去双层结构,释放的W1/O液滴聚集在一起而使粒径显著增加(P0.05)。经胃进入模拟肠道消化后,W1/O液滴破碎,平均粒径(d150 nm)显著减小(P0.05),此时具有最高的抗氧化活性。结果表明,W_1/O/W_2型乳液能有效地保护ACNs免受体外口腔和胃消化的影响,并可靶向地在模拟小肠内传递和释放。     

脂肪酸位置分布对婴幼儿奶粉油脂乳液体外模拟消化的影响

模拟婴儿胃、肠环境对两种婴幼儿配方奶粉油脂制备的乳液进行体外模拟消化研究,测定其体外胃、肠消化率,平均粒径、电位和微观结构的变化,以及消化后游离脂肪酸和甘油单酯的组成。结果表明:模拟胃液消化30 min,OPO型油脂乳液的消化程度大于普通型油脂乳液,而胃、肠最终消化程度普通型油脂乳液消化程度大于OPO型油脂乳液。消化过程OPO型油脂乳液zeta电位值高于普通型油脂乳液。胃、肠消化150 min,普通型油脂生成较多的饱和游离脂肪酸和不饱和脂肪酸甘油单酯,OPO型油脂生成的是游离不饱和脂肪酸,饱和脂肪酸甘油单酯含量较高。乳液消化过程中平均粒径、电位变化,结合共聚焦显微图像证明脂肪酸的位置分布影响产物的生成,而不同的产物影响消化中油滴的界面组成,从而影响其油脂的消化。     

红树莓籽黄酮微胶囊工艺优化及其体外模拟胃肠消化

以红树莓籽黄酮为芯材,明胶和羧甲基纤维素钠为壁材,通过单因素及响应面试验优化复凝聚法制备红树莓籽黄酮微胶囊工艺,并对黄酮微胶囊化前后理化性质和体外胃肠消化释放量进行分析。结果表明,黄酮微胶囊最佳制备工艺:芯壁比1:4.6(w:w)、壁材浓度1%、反应温度46 ℃,此条件下黄酮包埋率92.38%,水分含量5.26%、休止角31.3 °、溶解度91.54%、粒径546 nm、玻璃化转变温度145.75 ℃,具有良好的溶解性和稳定性。模拟胃消化2.5 h,黄酮包埋前后释放量分别为77.31和21.88 mg/g;肠消化3.0 h,黄酮包埋前后释放量分别为158.48和112.51 mg/g,表明黄酮微胶囊可提高黄酮稳定性和缓释效果。     

大黄鱼卵分离蛋白乳液的构筑及其体外消化规律

为了提高β-胡萝卜素的溶解性以及生物利用度,以大黄鱼卵分离蛋白(Pseudosciaena crocea roe protein isolate,PRPI)为乳化剂构建稳定的PRPI-β-胡萝卜素水包油乳液体系,考察不同贮存时间下乳液体系稳定性的变化;通过体外模拟消化明确其消化过程及吸收能力。结果表明,在贮存14 d后,乳液体系的平均粒径及外观形态均无显著改变;模拟口腔消化对乳液体系微观结构的状态影响较小,但经胃消化后,乳液体系发生水解,液滴聚集,平均粒径由(255.46±7.41)nm增大至(9 749.25±406.66)nm(P0.05);经小肠消化后,液滴聚集减弱,平均粒径减小至(3 654.36±527.91)nm(P0.05),仍有较高的β-胡萝卜素保留率(81.64±2.72)%和生物利用度(93.13±3.59)%。因此,以PRPI为乳化剂不仅可以提高乳液输送体系的稳定性,还可以提高β-胡萝卜素的生物利用度。     

紫苏油多层乳液的制备及乳液油脂体外消化特性

针对紫苏油在贮藏过程中极易氧化的特点,以大豆分离蛋白、壳聚糖和海藻酸钠为乳化剂,采用静电层层自组装技术对紫苏油进行包封,使紫苏油保持良好的物理稳定性,并能达到油脂缓释的目的。分别对紫苏油单层乳液、双层乳液和三层乳液微观形态和稳定性进行考察,建立体外模拟消化模型,通过气相色谱测定3 种乳液消化前后的脂肪酸组成。结果表明：壁材质量分数为大豆分离蛋白1.0%、壳聚糖2.0%、海藻酸钠1.5%时制备的3 种乳液粒径较小、电位较高,具有良好的理化稳定性。在酸性条件下的多层乳液能够更好保护多不饱和脂肪酸,随着包埋层数的增加,紫苏油的氧化速率越慢。体外模拟消化结果表明三层乳液较单层和双层乳液具有更好的缓释效果,多层乳液可以保证油脂中脂肪酸有效释放。本实验阐明不同界面层对紫苏油消化和脂肪酸释放特性的影响,为指导油脂缓释体系加工提供一定的参考。     

Coalescence Index of Protein-Stabilized Emulsions

A simple method is proposed to estimate coalescence stability of protein-stabilized emulsions. Coalescence was accelerated through agitation and measured by change in emulsion turbidity over time. A coalescence index (CI) was determined and used to compare emulsions stabilized with casein, whey (WPI) and soy protein isolates (SPI). CI increased when stirring rate increased. Casein produced more stable emulsions, followed by WPI and SPI. High homogenization pressure increased coalescence stability of WPI and SPI-stabilized emulsions and decreased coalescence stability of casein-stabilized emulsions. Microscopic examination, showed agitation of the emulsion had clearly induced formation of large oil droplets which acted as coalescence nuclei.     

Emulsifying Properties of Whey Protein-Carboxymethylcellulose Complexes

ABSTRACT: Proteins/polysaccharides complexes could improve emulsifying properties of proteins by thickening the layer at the interface of the oil droplets. Emulsifying properties of whey protein-carboxymethylcellulose complexes (WPI/CMC) were compared with those of a whey protein isolate (WPI). Ingredients were incorporated into oilinwater emulsions with various protein and oil contents. Visual observations, protein load, protein distribution and rheological measurements were used to evaluate emulsion stability. Protein load up to 26.1 and 48.9 mg protein/g oil were obtained for WPI and WPI/CMC emulsions, respectively. The higher protein load of WPI/CMC emulsions and visual observations indicated that WPI/CMC complexes had greater emulsifying properties against coalescence than whey proteins. However, complexes enhanced flocculation of oil droplets.     

COLD GELATION OF WHEY PROTEIN EMULSIONS

Stable and homogeneous emulsion‐filled gels were prepared by cold gelation of whey protein isolate (WPI) emulsions. A suspension of heat‐denatured WPI (soluble WPI aggregates) was mixed with a 40% (w/w) oil‐in‐water emulsion to obtain gels with varying concentrations of WPI aggregates and oil. For emulsions stabilized with native WPI, creaming was observed upon mixing of the emulsion with a suspension of WPI aggregates, likely as a result of depletion flocculation induced by the differences in size between the droplets and aggregates. For emulsions stabilized with soluble WPI aggregates, the obtained filled suspension was stable against creaming, and homogeneous emulsion‐filled gels with varying protein and oil concentrations were obtained. Large deformation properties of the emulsion‐filled cold‐set WPI gels were determined by uniaxial compression. With increasing oil concentration, the fracture stress increases slightly, whereas the fracture strain decreases slightly. Small deformation properties were determined by oscillatory rheology. The storage modulus after 16 h of acidification was taken as a measure of the gel stiffness. Experimental results were in good agreement with predictions according to van der Poel's theory for the effect of oil concentration on the stiffness of filled gels. Especially, the influence of the modulus of the matrix on the effect of the oil droplets was in good agreement with van der Poel's theory.     

Ability of whey protein isolate and/or fish gelatin to inhibit physical separation and lipid oxidation in fish oil-in-water beverage emulsion

The effect of pH on the capability of whey protein isolate (WPI) and fish gelatin (FG), alone and in conjugation, to form and stabilize fish oil-in-water emulsions was examined. Using layer-by-layer interfacial deposition technique for WPI–FG conjugate, a total of 1% protein was used to prepare 10% fish oil emulsions. The droplets size distributions and electrical charge, surface protein concentration, flow and dynamic rheological properties and physiochemical stability of emulsions were characterize at two different pH of 3.4 and 6.8 which were selected based on the ranges of citrus and milk beverages pHs, respectively. Emulsions prepared with WPI–FG conjugate had superior physiochemical stability compare to the emulsions prepared with individual proteins. Higher rate of coalescence was associated with reduction in net charge and consequent decrease of the repulsion between coated oil droplets due to the proximity of pH to the isoelectric point of proteins. The noteworthy shear thinning viscosity, as an indication of flocculation onset, was associated with whey protein stabilized fish oil emulsion prepared at pH of 3.4 and gelatin stabilized fish oil emulsion made at pH of 6.8. At pH 3.4, it appeared that lower surface charge and higher surface area of WPI stabilized emulsions promoted lipid oxidation and production of hexanal.     

Impact of whey protein – Beet pectin conjugation on the physicochemical stability of β-carotene emulsions

The aim of the present study was to investigate the impact of whey protein isolate (WPI)-beet pectin conjugation on the physical and chemical properties of oil-in-water emulsions incorporating β-carotene within the oil droplets. Covalent coupling of WPI to beet pectin was achieved by dry heating of WPI-beet pectin mixtures of different weight ratios at 80, 90, 100 °C and 79% relative humidity for incubation times ranging from 1 to 9 h. It was confirmed by SDS-polyacrylamide gel electrophoresis that WPI covalently linked to beet pectin. The physical and chemical stability of β-carotene emulsions was characterized by droplet size and distribution, transmission profiles using novel centrifugal sedimentation technique, microstructure and β-carotene degradation during the storage. Compared with those stabilized by WPI alone and unheated WPI-beet pectin mixtures, β-carotene emulsions stabilized by WPI-beet pectin conjugates had much smaller droplet sizes, more homogenous droplet size distribution, less change in centrifugal transmission profiles and obviously improved freeze–thaw stability, indicating a very substantial improvement in the physical stability. Rheological analysis exhibited that emulsions stabilized by WPI-beet pectin conjugates changed from a shear thinning to more like Newtonian liquid compared those with WPI alone and unheated WPI-beet pectin mixtures. Degradation of β-carotene in emulsion during storage was more obviously retarded by WPI-beet pectin conjugate than WPI and unheated WPI-beet pectin mixture, probably due to a thicker and denser interfacial layer in emulsion droplets. These results implied that protein–polysaccharide conjugates were able to improve the physical stability of β-carotene emulsion and inhibit the deterioration of β-carotene in oil-in-water emulsions.     

Stability of citral in protein- and gum arabic-stabilized oil-in-water emulsions

Citral is a major flavor component of citrus oils that can undergo chemical degradation leading to loss of aroma and formation of off-flavors. Engineering the interface of emulsion droplets with emulsifiers that inhibit chemical reactions could provide a novel technique to stabilize citral. The objective of this study was to determine if citral was more stable in emulsions stabilized with whey protein isolate (WPI) than gum arabic (GA). Degradation of citral was equal to or less in GA- than WPI-stabilized emulsion at pH 3.0 and 7.0. However, formation of the citral oxidation product, p-cymene was greater in the GA- than WPI-stabilized emulsion at pH 3.0 and 7.0. Emulsions stabilized by WPI had a better creaming stability than those stabilized by GA because the protein emulsifier was able to produce smaller lipid droplets during homogenization. These data suggest that WPI was able to inhibit the oxidative deterioration of citral in oil-in-water emulsions. The ability of WPI to decrease oxidative reactions could be due to the formation of a cationic emulsion droplet interface at pH 3.0 which can repel prooxidative metals and/or the ability of amino acids in WPI to scavenge free radical and chelate prooxidative metals.     

Impact of dietary fiber coatings on behavior of protein-stabilized lipid droplets under simulated gastrointestinal conditions

Multilayer emulsions containing lipid droplets coated by lactoferrin (LF) - anionic polysaccharide layers have improved resistance to environmental stresses (such as pH, salt, and temperature), but their behavior within the gastrointestinal tract (GIT) is currently unknown. The objective of this research was therefore to monitor changes in the physicochemical properties and digestibility of these systems under simulated GIT conditions. Primary emulsions (5% corn oil, 0.5% LF) were prepared using a high-pressure homogenizer. Secondary emulsions (5% corn oil, 0.5% LF, 0.5% polysaccharide) were prepared by incorporating alginate, low methoxyl pectin (LMP) or high methoxyl pectin (HMP) into primary emulsions. Emulsions were then subjected to simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) conditions in sequence. LF, LF-LMP and LF-HMP emulsions were stable to droplet aggregation in the stomach but aggregated in the small intestine, whereas LF-alginate emulsions aggregated in both the stomach and small intestine. The presence of a dietary fiber coating around the initial lipid droplets had little influence on the total extent of lipid digestion in SIF, but LF-alginate emulsions had a slower initial digestion rate than the other emulsions. These results suggest that the dietary fiber coatings may become detached in the small intestine, or that they were permeable to digestive enzymes. Pepsin was found to have little influence on the physical stability or digestibility of the emulsions. The knowledge obtained from this study is important for the design of delivery systems for encapsulation and release of lipophilic bioactive ingredients.     

Physicochemical Properties of Whey Protein-Stabilized Emulsions as affected by Heating and Ionic Strength

Corn oil-in-water emulsions (19.6 wt%; d₃₂～ 0.6 μm) stabilized by 2 wt% whey protein isolate (WPI) were prepared with a range of pH (3–7) and salt concentrations (0–100 mM NaCl). These emulsions were heated between 30 and 90°C and their particle size distribution, rheological properties and susceptibility to creaming measured. Emulsions had a paste-like texture around the isoelectric point of WPI (～φ 5) at all temperatures, but tended to remain fluid-like at pH >6 or <4. Heating caused flocculation in pH 7 emulsions between 70 and 80°C (especially at high salt concentrations), but had little effect on pH 3 emulsions. Flocculation increased emulsion viscosity and creaming. Results were interpreted in terms of colloidal interactions between droplets.     

Characterization of Chemically and Thermally Treated Oil‐in‐Water Heteroaggregates and Comparison to Conventional Emulsions

Heteroaggregated oil‐in‐water (O/W) emulsions formed by targeted combination of oppositely charged emulsion droplets were proposed to be used for the modulation of physical properties of food systems, ideally achieving the formation of a particulate 3‐dimensional network at comparably low‐fat content. In this study, rheological properties of Quillaja saponins (QS), sugar beet pectin (SBP), and whey protein isolate (WPI) stabilized conventional and heteroaggregated O/W emulsions at oil contents of 10% to 60% (w/w) were investigated. Selected systems having an oil content of 30% (w/w) and different particle sizes (d₄₃ ≤ 1.1 or ≥16.7 μm) were additionally subjected to chemical (genipin or glutaraldehyde) and thermal treatments, aiming to increase network stability. Subsequently, their rheological properties and stability were assessed. Yield stresses (τ₀) of both conventional and heteroaggregated O/W emulsions were found to depend on emulsifier type, oil content, and initial droplet size. For conventional emulsions, high yield stresses were only observed for SBP‐based emulsions (τ₀,_SBP approximately 157 Pa). Highest yield stresses of heteroaggregates were observed when using small droplets stabilized by SBP/WPI (approximately 15.4 Pa), being higher than those of QS/WPI (approximately 1.6 Pa). Subsequent treatments led to significant alterations in rheological properties for SBP/WPI systems, with yield stresses increasing 29‐fold (glutaraldehyde) and 2‐fold (thermal treatment) compared to untreated heteroaggregates, thereby surpassing yield stresses of similarly treated conventional SBP emulsions. Genipin‐driven treatments proved to be ineffective. Results should be of interest to food manufacturers wishing to design viscoelastic food emulsion based systems at lower oil droplet contents.     

脱酰胺马铃薯蛋白乳液的制备及其微流变特性

以脱酰胺马铃薯蛋白为原料制备乳液，研究不同脱酰胺时间（0、0.5、3、6、12 h）的马铃薯蛋白乳液的粒径分布、乳化稳定性、微流变特性及微观结构的变化。结果表明，随着脱酰胺时间的延长，乳液粒径（体积平均直径）和稳定性动力学指数值均呈现先减小后增大的趋势；脱酰胺3 h和6 h的马铃薯蛋白乳液粒径分布均匀，乳液较为稳定，可能是因为改性蛋白乳液液滴间静电斥力增大，阻止了液滴的聚集；脱酰胺12 h的马铃薯蛋白乳液粒径增大，乳液稳定性减小，这可能是因为电荷斥力降低使液滴聚集。微流变特性分析表明脱酰胺6 h的马铃薯蛋白乳液的宏观黏度因子值最高，黏度最大，粒子运动速度减慢，乳液液滴间具有强作用力，体系更稳定。本研究为马铃薯蛋白的深入研究及产品开发提供一定参考，提高马铃薯蛋白的利用率，扩大应用范围。