不同乳化剂对姜黄素乳液理化稳定性的影响

姜黄素具有许多生物活性功能,但较差的溶解度和稳定性限制了其在食品和医药领域的应用。为筛选出具有良好稳定性的姜黄素乳液,本研究以亚麻籽油为姜黄素的油相载体,经高压均质法制备出姜黄素乳液中研究卵磷脂、吐温-80、阿拉伯胶和乳清分离蛋白4种食品级乳化剂对姜黄素乳液的理化特性和贮藏稳定性的影响,从包埋率、浊度、粒径、电位等方面进行稳定性评价。结果表明,吐温-80稳定的姜黄素乳液中姜黄素包埋率较高(76.98%),浊度和平均粒径最小,分别为848.0 NTR、214.23±1.52 nm;同时在贮藏期内姜黄素乳液的平均粒径变化最小,增长不到1%,贮藏稳定性表现良好。同时,4℃低温条件下姜黄素保留率最高,达到88.02%。结果表明,选用吐温-80作为乳化剂,姜黄素乳液具有最好的溶解性和稳定性,这为今后姜黄素在食品工业中的广泛应用提供了新思路。     

短链葡聚糖-姜黄素纳米乳液的制备及结构表征

利用短链葡聚糖(short glucan chains,SGC)的螺旋空间结构来包埋姜黄素(curcumin,CUR)。通过使用高剪切分散乳化机高速剪切溶液5 min,用纳米均质机在50 MPa压力下高压均质经剪切后的乳液2次制备成纳米乳液以提高其包埋率和载药量。XRD (x-ray diffraction)和TGA (thermogravimetric analysis)很好的验证了包合物的形成,通过TGA、SEM (scanning electron microscopy)、激光粒径分析仪等各种表征分析得出短链葡聚糖-姜黄素纳米乳液制备成功,所制得的乳液对姜黄素的包埋率和载药量都高于短链葡聚糖-姜黄素包合物,分别达到了71.11%和12.07%,说明制备成纳米乳液对姜黄素的包埋率和载药量都有了明显的提高。所制备的纳米乳液的粒径小于300 nm,粒径分布均一,Zeta电位观测表明所制得的乳液的稳定性有所提高。为提高食品及医药领域姜黄素的生物利用率提供了一定的参考意义。     

Stability of chitosan nanoparticles for L-ascorbic acid during heat treatment in aqueous solution

This study investigated the stability and characteristics of L-ascorbic acid (AA)-loaded chitosan (CS) nanoparticles during heat processing in aqueous solutions. AA-loaded CS nanoparticles were prepared by ionic gelation of CS with tripolyphosphate (TPP) anions. The smallest CS nanoparticles (170 nm) were obtained with a CS concentration of 1.5 mg/mL and a TPP concentration of 0.6 mg/mL. As the concentration of AA increased from 0.1 to 0.3 mg/mL, the particle size increased, while the zeta potential decreased, and the encapsulation efficiency of AA remained within a fixed range (10-12%). During heat processing at various temperatures, the size and zeta potential of the particles decreased rapidly in the first 5 min and then slowly fell to the regular range. At the beginning of the release profiles, the burst release-related stability of the surface increased with the temperature. Then, the release of the internal AA was constantly higher with a longer release time. Consequently, it was confirmed that the stability of AA-loaded CS nanoparticles was affected by temperature but that the internal stability was greater than the surface stability. These results demonstrate the stability of CS nanoparticles for AA during heat processing and suggest the possible use of AA-loaded CS nanoparticles to enhance antioxidant effects because of the continuous release of AA from CS nanoparticles in food processing.     

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。     

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.     

稀释介质种类对豆乳蛋白胶体粒子zeta电位测定效果的影响

蛋白粒子zeta电位是衡量豆乳体系稳定性的一个重要指标,而在电位分析前常采用稀释介质对豆乳进行预处理。为了确保zeta电位测定的准确性和科学性,必须选择合适的稀释介质。因此,该研究采用去离子水、豆乳超滤液两种稀释介质分别对豆乳进行稀释,并比较了这2种稀释介质对zeta电位、粒径分布、pH值以及电导率的影响。结果表明,若以去离子水为稀释介质,zeta电位的绝对值会随着稀释倍数的升高而显著增加（*P<0.05）,这主要是由于豆乳蛋白胶体粒子发生解聚导致粒径减小,而pH值的升高和电导率的降低则说明豆乳的离子强度显著降低。相比之下,选用豆乳超滤液稀释豆乳时,体系的 zeta 电位、粒径分布、pH值以及电导率都未随稀释倍数的增加而改变（*P>0.05）,说明此法能够较好地维持豆乳蛋白粒子的荷电稳定性。由此可知,豆乳超滤液可做为豆乳zeta电位测定的理想稀释介质。     

Effects of protein and peptide addition on lipid oxidation in powder model system

The effect of protein and peptide addition on the oxidation of eicosapentaenoic acid ethyl ester (EPE) encapsulated by maltodextrin (MD) was investigated. The encapsulated lipid (powder lipid) was prepared in two steps, i.e., mixing of EPE with MD solutions (+/- protein and peptides) to produce emulsions and freeze-drying of the resultant emulsions. EPE oxidation in MD powder progressed more rapidly in the humid state [relative humidity (RH) = 70%] than in the dry state (RH = 10%). The addition of soy protein, soy peptide, and gelatin peptides improved the oxidation stability of EPE encapsulated by MD, and the inhibition of lipid oxidation by the protein and the peptides was more dramatic in the humid state. Especially, the oxidation of EPE was almost perfectly suppressed when the lipid was encapsulated with MD + soy peptide during storage in the humid state for 7 days. Several physical properties such as the lipid particle size of the emulsions, the fraction of nonencapsulated lipids, scanning electron microscopy images of powder lipids, and the mobility of the MD matrix were investigated to find the modification of encapsulation behavior by the addition of the protein and peptides, but no significant change was observed. On the other hand, the protein and peptides exhibited a strong radical scavenging activity in the powder systems as well as in the solution systems. These results suggest that a chemical mechanism such as radical scavenging ability plays an important role in the suppression of EPE oxidation in MD powder by soy proteins, soy peptides, and gelatin peptides.     

Development of zein nanoparticles coated with carboxymethyl chitosan for encapsulation and controlled release of vitamin D3

In this study, zein nanoparticles coated with carboxymethyl chitosan (CMCS) were prepared to encapsulate vitamin D3 (VD3). VD3 was first encapsulated into zein nanoparticles using a low-energy phase separation method and coated with CMCS simultaneously. Then, calcium was added to cross-link CMCS to achieve thicker and denser coatings. The nanoparticles with CMCS coatings had a spherical structure with particle size from 86 to 200 nm. The encapsulation efficiency was greatly improved to 87.9% after CMCS coating, compared with 52.2% for that using zein as a single encapsulant. The physicochemical properties were characterized by differential scanning calorimetry and Fourier transform infrared spectroscopy. Nanoparticles with coatings provided better controlled release of VD3 in both PBS medium and simulated gastrointestinal tract. Photostability against UV light was significantly improved after encapsulation. Encapsulation of hydrophobic nutrients in zein nanoparticles with CMCS coatings is a promising approach to enhance chemical stability and controlled release property.     

Curcumin nanoparticles: preparation, characterization, and antimicrobial study

Curcumin is a highly potent, nontoxic, bioactive agent found in turmeric and has been known for centuries as a household remedy to many ailments. The only disadvantage that it suffers is of low aqueous solubility and poor bioavailability. The aim of the present study was to develop a method for the preparation of nanoparticles of curcumin with a view to improve its aqueous-phase solubility and examine the effect on its antimicrobial properties. Nanoparticles of curcumin (nanocurcumin) were prepared by a process based on a wet-milling technique and were found to have a narrow particle size distribution in the range of 2-40 nm. Unlike curcumin, nanocurcumin was found to be freely dispersible in water in the absence of any surfactants. The chemical structure of nanocurcumin was the same as that of curcumin, and there was no modification during nanoparticle preparation. A minimum inhibitory concentration of nanocurcumin was determined for a variety of bacterial and fungal strains and was compared to that of curcumin. It was found that the aqueous dispersion of nanocurcumin was much more effective than curcumin against Staphylococcus aureus , Bacillus subtilis , Escherichia coli , Pseudomonas aeruginosa , Penicillium notatum , and Aspergillus niger . The results demonstrated that the water solubility and antimicrobial activity of curcumin markedly improved by particle size reduction up to the nano range. For the selected microorganisms, the activity of nanocurcumin was more pronounced against Gram-positive bacteria than Gram-negative bacteria. Furthermore, its antibacterial activity was much better than antifungal activity. The mechanism of antibacterial action of curcumin nanoparticles was investigated by transmission electron micrograph (TEM) analysis, which revealed that these particles entered inside the bacterial cell by completely breaking the cell wall, leading to cell death.     

Study of the effect of soy proteins on the acid-induced gelation of casein micelles

The objective of this research was to understand whether addition of soy protein to milk protein affects the properties of acid-induced casein gels. Different samples were prepared by suspending casein micelles pellets in milk serum containing soy proteins or whey proteins as well as mixtures of the two proteins. Glucono-delta-lactone was added, and the changes in apparent size (in diluted systems) as well as the viscoelastic properties of the mixtures were measured. Size exclusion chromatography was also carried out to characterize the soluble phase of the various mixtures before and after heating. Soy protein affected the gelation of the mixtures; however, not to the same extent as whey proteins, which dominated formation of the network in soy-whey-casein systems. It was concluded that, up to a critical ratio of soy/whey proteins, soy proteins can be incorporated in the mix without a significant change in structure of the casein gels.     

Effects of mass ratio, pH, temperature, and reaction time on fabrication of partially purified pomegranate ellagitannin-gelatin nanoparticles

Nanoparticles were fabricated using self-assembly between partially purified ellagitannins (PPE) and gelatin. The factors affecting fabrication of nanoparticles, including PPE-to-gelatin mass ratio, pH, temperature, and reaction time, were investigated and the characteristics of formed nanoparticles, including sizes, zeta-potentials, and loading efficiency, were assessed. Nanoparticles that were fabricated using PPE-to-gelatin mass ratio from 1:5 to 6:5 had particle sizes from 121.5 to 129.0 nm. Increasing the ratio to 9:5 caused a drastic increase of particle size (620.7 nm) and was accompanied by formation of precipitation in the colloidal system. Nanoparticles fabricated in the pH range 4.0 to 5.3 (gelatin solution) had particle sizes ranging from 20.6 to 193.9 nm and zeta-potential between +14.7 and +23.8 mV, respectively. Loading efficiency of punicalagin A and B in the nanoparticles under these pH values ranged from 29.5% to 84.3% and from 10.6% to 73.9%, respectively. Extreme pH of gelatin solutions (pH 1.0, 2.0, 3.0, or 11.0) hindered the formation of nanoparticles due to possible hydrolyzation of ellagitannins and weakened affinity between ellagitannins and gelatin. Although gelatin at isoelectric point (pH 6-7) provided more hydrophobic sites to interact with ellagitannins, weakened zeta-potentials resulted in poor stability of nanoparticle suspension. Nanoparticles formed between 25 to 50 °C had particle size below 500 nm, whereas lower temperatures increased the size of nanoparticles. Nanoparticles were formed after 12 h of reaction time, and the nanoparticle colloidal suspension remained stable for 4 days. PPE-gelatin nanoparticles fabricated using PPE-to-gelatin mass ratio below 7:5, pH 4.0, temperature 25-40 °C, and reaction time 1.5 days had smaller particle sizes, higher zeta-potentials, and good loading efficiency.     

Effect of different preparation methods on physicochemical properties of salidroside liposomes

Salidroside liposomes were prepared by using five different methods: thin film evaporation, sonication, reverse phase evaporation, melting, and freezing-thawing. The effect of different preparation methods and salidroside loading capacity on the formation of liposomes and their physicochemical properties were evaluated by means of encapsulating efficiency, particle size, morphology, and zeta potential. Results showed that the encapsulating efficiency of liposomes was highest when prepared by freezing-thawing, followed by thin film evaporation, then reverse phase evaporation and the lowest with melting and sonication. Loading capacity of salidroside had a significant effect on encapsulating efficiency, average diameter, and zeta potential of liposomes. Liposomal systems prepared by sonication, melting, and reverse phase evaporation displayed better dispersivity. Determination of leakage of salidroside from different liposomal systems revealed that the melting method had the lowest leakage of 10% and 15%, at 4 and 30 degrees C after 1 month of storage, respectively. In all cases, a straight-line leakage behavior of salidroside was found. This revealed that the leakage of salidroside was a diffusion process from the membrane of liposomes. Furthermore, the storage stability of different liposomal systems showed that salidroside liposomes prepared by melting had a better physicochemical stability. Instability in the systems was exacerbated when temperature increased. Salidroside liposomes showed the slower increase in particle size than liposomes without salidroside. This could indicate that salidroside played an important role in preventing the aggregation and fusion of liposomes.     

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     

冷冻方式对醛交联大豆蛋白多孔材料结构及吸附特性的影响

为制备纳米级孔径的大豆蛋白多孔材料,研究了冰箱和液氮冷冻处理的醛交联大豆蛋白多孔材料的结构及吸附性能。结果表明:戊二醛对大豆蛋白的交联效果优于甲醛和乙二醛。液氮冷冻处理的多孔材料比表面积和孔容均较大,而平均孔径较小;纳米级孔的孔径都分布在80 nm以内,介孔总孔容占比超过50%,大孔次之,微孔占比最小;冰箱冷冻样品纳米级孔的孔径主要分布在70 nm以内,且微孔和介孔孔容都小于采用液氮冷冻处理的样品。场发射扫描电镜分析表明,大豆蛋白多孔材料的孔形态为微米级圆孔和纳米级狭缝孔。冷冻处理比醛类交联剂对孔结构的影响大,合适的冷冻方式能替代或超过交联剂种类变化取得的效果。热重分析表明液氮冷冻处理的戊二醛交联大豆蛋白多孔材料热稳定性好;该多孔材料对对硝基苯酚和六价铬离子具有一定的吸附效果,是制备大豆蛋白多孔材料较合适的方法。研究结果为植物蛋白多孔材料的制备提供参考。     

Physicochemical and Functional Properties of Protein Isolates Obtained from Several Pea Cultivars

The goal of this research was to investigate the physicochemical and functional properties of protein isolates obtained from several pea cultivars grown at two locations in Canada. The functionalities of the pea protein isolates (PPIs) were then compared with those of commercial food protein ingredients derived from milk, egg, pea, soy, and wheat. Six pea cultivars (Agassiz, CDC Golden, CDC Dakota, CDC Striker, CDC Tetris, and Cooper) were collected from two years over two locations in Saskatchewan (Canada). Samples were evaluated for composition, surface properties, and functional properties. All PPIs had protein levels of ≈91% (db) and isolate and protein yields of ≈18 and ≈72%, respectively. Cultivars exhibited legumin/vicilin ratios from 0.36 (Agassiz) to 0.79 (CDC Golden). Differences among cultivars as well as significant cultivar × environment interactions were found only for maximum intrinsic fluorescence (195–267 arbitrary units), solubility (63–75%), and foaming capacity (167–244%). No differences owing to either cultivar or environment were observed for surface charge (zeta potential = approximately –24 mV), oil holding capacity (≈3.2 g/g), foam stability (≈75%), or emulsion stability (≈96%). Relative to the commercial isolates, PPIs prepared under laboratory conditions behaved most similarly to soy isolates, with the exception of solubility. Whey and egg were superior in solubility and foaming properties, whereas wheat and the commercial pea protein product were significantly lower in nearly all of the functionality tests. Based on their oil holding properties, the laboratory‐prepared PPIs may serve as good meat extenders. The findings also suggest that pea processors may not need to specify either the cultivar or the environment when acquiring raw material, thus creating advantages in their feedstock sourcing.     

蛋白水解物改性脲甲醛缓释肥的结构及氮素释放特征

针对脲甲醛养分释放与作物生长曲线不匹配的问题,该研究采用蛋白水解物来改善脲甲醛的氮素释放率。土柱淋洗结果表明,蛋白水解物降低了脲甲醛初期的氮素释放率,加快了脲甲醛在后期的氮素释放率。在当量尿素与甲醛的摩尔比为1.2时,蛋白水解物水解度越小,氮素释放率越快。到第7周,蛋白水解物改性脲甲醛的氮素释放率和未改性的脲甲醛相比,氮素释放率提高了58.9%。采用傅里叶红外光谱、X射线衍射、热重和扫描电镜分析了蛋白水解物和蛋白水解物改性脲甲醛的结构,发现:蛋白水解物的活性基团能够与甲醛反应,并与尿素聚合,以嵌段的方式引入到脲甲醛的分子结构中;蛋白水解物水解度越低,改性脲甲醛结晶度降低的越多;和未改性的脲甲醛相比,改性的脲甲醛的最大分解温度有所降低,并且改性后的脲甲醛疏松多孔。因此,可以通过蛋白水解物的水解度来调控改性脲甲醛的氮素释放率,进而适应不同作物的生长周期,提高氮肥的利用率。     

Beta-conglycinin embeds active peptides that inhibit lipid accumulation in 3T3-L1 adipocytes in vitro

Obesity is a worldwide health concern because it is a well-recognized predictor of premature mortality. The objective was to identify soybean varieties that have improved potential to inhibit fat accumulation in adipocytes by testing the effects of soy hydrolysates having a range of protein subunit compositions on lipid accumulation and adiponectin expression in 3T3-L1 adipocytes. The results showed that differences in the protein distribution of 15 soy genotypes led to different potentials for the reduction of fat accumulation. The inhibition of lipid accumulation of soy alcalase hydrolysates in 3T3-L1 adipocytes ranged from 29 to 46%. Soy hydrolysates made from genotypes with 45.3 +/- 3.3% of total protein as beta-conglycinin, on average, showed significantly higher inhibition of lipid accumulation compared to those with 24.7 +/- 1.5% of extracted total protein as beta-conglycinin. Moreover, after in vitro simulated digestion with pepsin-pancreatin of the soy alcalase hydrolysates, 86% of the original activity remained. Adiponectin expression was induced in 3T3-L1 adipocytes treated with 15 soy hydrolysates up to 2.49- and 2.63-fold for high and low molecular weight adiponectin, respectively. The inhibition of lipid accumulation calculated from a partial least squares (PLS) analysis model correlated well with experimental data (R(2) = 0.91). In conclusion, it was feasible to differentiate soy varieties on the basis of the potential of their proteins to reduce fat accumulation using a statistical model and a cell-based assay in vitro. Furthermore, beta-conglycinin embeds more peptides than glycinin subunits that inhibit lipid accumulation and induce adiponectin in 3T3-L1 adipocytes. Therefore, soy ingredients containing beta-conglycinin may be important food components for the control of lipid accumulation in adipose tissue.     

Formation of cholesterol oxidation products in marinated foods during heating

The objectives of this study were to develop a gas chromatography-mass spectrometry (GC-MS) method to analyze the contents of cholesterol oxidation products (COPs) in marinated eggs, pork, and juice and to compare the effect of heating time and soy sauce or sugar on the formation of COPs. By using a silica cartridge for purification and GC-MS with selected ion monitoring for detection, seven COPs, including 7alpha-hydroxycholesterol, 7beta-hydroxycholesterol, 5,6alpha-epoxycholesterol, 5,6beta-epoxycholesterol, 5alpha-cholestane-3beta, 5,6beta-triol, 5-cholesten-3beta-25-diol, and 7-ketocholesterol, as well as internal standard 5alpha-cholestane, were resolved within 16 min by using a HP-5MS capillary column. During marinating, the levels of most COPs followed an increasing trend with increasing heating time. However, a higher amount of COPs was generated for ground pork as compared to eggs. The incorporation of soy sauce or sugar (1 and 10%) was effective in inhibiting COPs formation, with the latter being more pronounced than the former in both marinated eggs and pork.     

Microencapsulating properties of sodium caseinate

Emulsions were prepared with 5% (w/v) solutions of sodium caseinate (Na Cas) and soy oil at oil/protein ratios of 0.25-3.0 by homogenization at 10--50 MPa. Emulsions were spray-dried to yield powders with 20--75% oil (w/w). Emulsion oil droplet size and interfacial protein load were determined. Microencapsulation efficiency (ME), redispersion properties, and structure of the powders were analyzed. The size of emulsion oil droplets decreased with increasing homogenization pressure but was not influenced by oil/protein ratio. Emulsion protein load values were highest at low oil/protein ratios. ME of the dried emulsions was not affected by homogenization pressure but decreased from 89.2 to 18.8% when the oil/protein ratio was increased from 0.25 to 3.0, respectively. Mean particle sizes of reconstituted dried emulsions were greater than those of the original emulsions, particularly at high oil/protein ratios (>1.0), suggesting destabilization of high-oil emulsions during the spray-drying process.     

Physicochemical properties of soy protein: effects of subunit composition

Soy protein elastomer (SPE) exhibits elastic, extensible, and sticky properties in its native state and displays great potential as an alternative to wheat gluten. The objective of this study was to better understand the roles of soy protein subunits (polypeptides) contributing to the functional properties of SPE. Six soy protein samples with different subunit compositions were prepared by extracting the proteins at various pH values on the basis of the different solubilities of conglycinin (7S) and glycinin (11S) globulins. Soy protein containing a large amount of high molecular weight aggregates formed from α' and α subunits exhibited stronger viscoelastic solid behavior than other soy protein samples in terms of dynamic elastic and viscous modules. Electrophoresis results revealed that these aggregates are mainly stabilized through disulfide bonds, which also contributed to higher denaturation enthalpy as characterized by DSC and larger size protein aggregates observed by TEM. Besides, the most viscoelastic soy protein sample exhibited flat and smooth surfaces of the protein particles as observed by SEM, whereas other samples had rough and porous particle surfaces. It was proposed that the ability of α' and α to form aggregates and the resultant proper protein-protein interaction in soy proteins are the critical contributions to the continuous network of SPE.