尿素改性大豆分离蛋白与粘胶共混性能的研究

通过尿素改性改变大豆分离蛋白(SPI)分子的空间结构,使其能更好地与粘胶共混。以共混膜中蛋白保留量为指标,考察了尿素浓度、SPI浓度、亚硫酸钠浓度、pH、温度的影响;并采用正交实验优化蛋白质改性条件。优化的改性条件为:尿素浓度6 mol/L,SPI浓度8%,亚硫酸钠浓度1.0%,pH 9,温度25℃,此时共混膜中蛋白保留量为13.87%。     

pH和金属离子对大豆分离蛋白凝胶形成影响

在90℃,研究大豆分离蛋白浓度、pH值、金属离子、加热时间等因素对大豆分离蛋白凝胶形成影响。结果显示,酸性条件下大豆分离蛋白形成凝胶最适pH为3．0,碱性条件下形成凝胶最适pH为9．0,pH大于11在95℃水浴锅中加热5 min,大豆分离蛋白变为黄棕色粘稠状液体,且有异味;凝胶溶液中CaCl2浓度为0．4％时,形成凝胶透明性最高,时间为22min。     

pH和金属离子对大豆分离蛋白凝胶形成的影响

在90℃，研究了大豆分离蛋白浓度、pH值、金属离子、加热时间等因素对大豆分离蛋白凝胶形成的作用。结果显示，酸性条件下大豆分离蛋白形成凝胶的最适pH为3．0，碱性条件下形成凝肢的最适pH为9．0,pH大于11在95℃的水浴锅中加热5min，大豆分离蛋白变为黄棕色粘稠状液体，且有异味；凝胶溶液中CaCl2浓度为0．4％时，形成凝胶的透明性最高，时间为22min。     

木瓜蛋白酶对大豆分离蛋白的水解作用研究

用木瓜蛋白酶对大豆分离蛋白进行了酶解研究,结果表明：以大豆分离蛋白作为底物,木瓜蛋白酶的反应动力学参数km值为0．34％,酶的最适反应pH值为7．5,在pH9．0的碱性条件下有较好的适应性。酶的最大反应温度为60℃,在此温度条件下,温浴180min仍能保持70％的酶活。2．0％~2．5％的大豆分离蛋白溶液经木瓜蛋白酶水解后,丝氨酸、苏氨酸、脯氨酸、组氨酸、蛋氨酸等游离或基酸含量明显增加,大豆多肽每100ml提高92~94mg,等电点分布范围变宽,由原来大豆分离蛋白的pH3．1~4．3变为pH3.1~5．5。     

热水浴-超声波对魔芋-大豆分离蛋白共混液溶胀特性的研究

探讨了大豆分离蛋白质量浓度、pH、热水浴温度、超声波功率和超声波时间对魔芋-大豆分离蛋白共混液黏度和溶胀时间的影响。研究结果表明:超声波处理能加强魔芋与大豆分离蛋白的分散性和相互作用;共混液的溶胀时间随着大豆分离蛋白质量浓度的增加和共混液pH的上升而延长,随着热水浴温度的升高、超声波功率和时间的增加而缩短;共混液的黏度随大豆分离蛋白质量浓度、pH、超声波功率和超声波时间的增加呈现先增加后减小的变化趋势,随着热水浴温度的升高一直减小。经拟合,黏度的变化规律与外界条件的四次方多项式呈高度相关性。     

大豆分离蛋白凝胶制备和凝胶质构特性研究

本研究以大豆分离蛋白为原料，考察蛋白质浓度、pH值、加热温度、加热时间对凝胶形成的影响，采用物性仪对不同务件下制备的凝胶的质构特性进行研究，不同评价指标得出的结论不尽相同。通过正交实验得出形成凝胶硬度最大的制备条件为：蛋白浓度12％，pH值6．5，加热温度95℃，加热时间35min；形成凝胶脆性最大的制备凝胶争件为：蛋白浓度12％，pH值7．0，加热温度95℃，加热时间25min；形成凝胶弹性最好的制备凝胶务件为：蛋白浓度12％，pH值7．0，加热温度85℃，加热时间35min；形成凝胶粘附性最大的制备凝胶条件为：蛋白浓度12％，pH值7．0，加热温度95℃，加热时间35min。     

菠萝蛋白酶水解大豆分离蛋白工艺优化研究

以水解度为指标，研究了温度、pH、底物浓度、酶浓度等因素对菠萝蛋白酶水解大豆分离蛋白的影响。影响菠萝蛋白酶水解大豆蛋白的影响因素顺次为酶浓度、温度、底物浓度、pH。最佳参数组合是酶浓度为6％、温度为65℃、底物浓度为5％、pH为8．0。在此条件下，菠萝蛋白酶水解大豆分离蛋白的水解度在半小时内可以达到8．18％。     

超滤膜法制备大豆分离蛋白工艺研究

探讨了从低变性脱脂豆粕中碱浸提大豆蛋白的工艺条件，依据正交实验确定的最佳工艺参数为：浸提3次，pH值9．0，固液比1：15，每次浸提时间30min，得到的蛋白提取率为87．97％。在此基础上研究了用中空纤维膜超滤技术从蛋白预过滤液中分离提纯大豆分离蛋白的工艺参数。通过单因素实验，分析了不同温度、压力、pH值对膜通量的影响，并通过正交实验确定膜分离的最佳温度、压力、pH值和时间分别为：45℃、0．08MPa、pH8．0和15min。     

Protamex复合蛋白酶水解大豆分离蛋白的研究

为优化大豆分离蛋白酶水解条件，本试验采用二次回归正交旋转组合设计方法对Protamex复合蛋白酶水解大豆分离蛋白的条件进行研究。建立了水解度(DH)与pH值、反应温度、反应时间、底物浓度、酶与底物浓度比之间的数学模型；并获得最佳水解工艺条件：pH值6．5，温度40℃，水解时间10h，底物浓度14％，酶与底物浓度比4．5％；主成分分析表明，pH对DH的贡献率最大。     

可食性大豆分离蛋白保鲜膜的研制

试验以大豆分离蛋白为主要原料,对其与甘油制膜的成膜工艺进行研究。通过单因素试验考察大豆分离蛋白与甘油的比例、成膜pH值及其成膜温度对保鲜膜的各项性能-透水率、透光率、断裂应力、延伸率,及水溶性的影响。试验结果表明:随蛋白与甘油比例增大膜性能先达到最大然后下降。成膜温度与膜性能正相关。pH值必须远离6,但pH值高于9时膜性能没有显著提高颜色却显著变黄。综合分析得出最佳成膜大豆分离蛋白与甘油的比例为2.5∶1,pH值为8,温度为95℃。     

十二烷基磺酸钠(SDS)在大豆分离蛋白基可食性膜中应用

该文报道研究十二烷基磺酸钠应用于以甘油作为增塑剂的大豆蛋白基可食性膜后对其物理性质影响。研究结果表明:当SDS添加量为40%(十二烷基磺酸钠质量/大豆分离蛋白质量)时,薄膜抗拉强度(TS)值显著(p<0.05)减少43%,最大断裂伸长率(E)值显著(p<0.05)增加至少5%,水分含量(MC)值显著减少(p<0.05),总可溶性物质含量(TSM)值显著增加(p<0.05);当SDS添加量>10%时,WVP值下降50%;SDS添加量为20%、30%、40%时,膜颜色值为显著+b (p<0.05),即黄色值增加。     

大豆分离蛋白发泡剂的泡沫染色

采用搅打发泡的方法研究了大豆分离蛋白浓度、pH值、表面活性剂对大豆分离蛋白泡沫性能的影响;选取多个有利于泡沫性能的因素,以大豆蛋白泡沫作为染料载体,选用活性黄染料对纯棉织物进行了泡沫染色的探究,测试了染色织物的匀染性、拉伸性和色牢度。结果表明,在pH值为7,大豆分离蛋白质量分数2%,十二烷基硫酸钠(SDS)质量浓度1g/L,Tween-80质量浓度2g/L的条件下,泡沫性能最优。泡沫染色织物的匀染性、色牢度均优于常规水浴染色,织物强力提高。     

酶改性大豆分离蛋白的制备及产品功能性的研究

为了改善碱溶酸沉法大豆分离蛋白产品(简称SPI)的功能性,采用有限酶解的方法,从6种蛋白酶中选出中性蛋白酶(Neutrase)作为改性用酶.通过单因素实验,分析了底物浓度,E/S,反应时间对水解度和氮收率的影响,并通过正交实验确定制备酶改性大豆分离蛋白(简称ESPI)的最佳工艺参数为:底物浓度为3%,E/S为1 200U/g,时间为60 min.得到的ESPI的蛋白含量与SPI相近,但NSI由SPI的90%提高到97%.而且在功能性方面,ESPI也得到了很好的改善,尤其是乳化性和起泡性.     

Thermorheological Characteristics of Soybean Protein Isolate

ABSTRACT: Small amplitude oscillation shear measurement was used to study gel rigidity of commercial soy protein isolate (SPI) dispersions during isothermal and non-isothermal heating. Temperature sweep data (20°C to 90°C atheating rate of 1°C/min) of SPI dispersions demonstrated that elastic modulus (G) predominates over viscous component (G') for all concentrations studied. The gelation kinetics of SPI was evaluated by a non-isothermal technique as a function of elastic modulus (G). During experiments, it was observed that a critical concentration of 10% was required to form a true SPI gel. Thermorheological data of 10% and 15% SPI dispersions were adequately fitted by 2nd-order reaction kinetics. The reaction order of gelation was initially calculated by multiple regression technique correlating dG'/dt, G'and temperature, which finally was verified by linear regression of kinetic equation at selected order. Isothermal data of 15% SPI was also followed by 2nd-order reaction kinetics. The activation energy during the isothermal technique was significantly higher than non-isothermal gelation of SPI at same concentration level. Gel strength of the non-isothermally heated SPI sample (15% to 20%) was compared with isothermally heated (90°C for 30 min) one. Higher protein concentration (20%) and isothermal heating exhibited significantly higher gel rigidity while the difference between the 2 processes was insignificant at 15% concentration at a similar condition.     

Gelling of microbial transglutaminase cross-linked soy protein in the presence of ribose and sucrose

Soy protein isolate (SPI) was incubated with microbial transglutaminase (MTGase) enzyme for 5 (SPI/MTG(5)) or 24 (SPI/MTG(24)) h at 40 °C and the cross-linked SPI obtained was freeze-dried, and heated with 2% (w/v) ribose (R) for 2 h at 95 °C to produce combined-treated gels. Longer incubation period resulted in more compact and less swollen SPI particle shape when reconstituted with sugar solution. Thus, this MTGase treatment affected samples in terms of flow behaviour and gelling capacity. Rheological study showed different gelling profiles with the cross-linking treatments and combined cross-linked SPI gave a higher G′ value compared to single treated samples. These are due to the formation of additional ε-(γ-glutamyl)lysine bonds and “Maillard cross-links” within the SPI protein network during the MTGase incubation and heating in the presence of ribose (i.e. reducing sugar). Network/non-network protein analysis found that network protein increased with cross-linking treatment, which also resulted in different SDS–PAGE profiles. As in non-network protein fraction, A₄ subunit was suggested to become part of the network protein as a result of combined cross-linking.     

冷冻诱导对大豆分离蛋白结构和聚集行为的影响

为研究冷冻处理下大豆分离蛋白宏观结构性质的改变与其在冷冻过程中发生的微观聚集行为的关联性,该文以大豆分离蛋白溶液为原料,在-5、-20℃的条件下冷冻诱导后烘干再溶解,研究大豆分离蛋白溶液的浓度、冷冻诱导温度和时间对大豆分离蛋白聚集态的影响。通过溶解性、浊度等指标对大豆分离蛋白的聚集性行为进行分析,以电镜、稳定性动力学指数等指标对大豆分离蛋白的微观分子结构进行分析。结果表明,冷冻处理时间与大豆分离蛋白的溶解性大小成负相关,在-5℃冷冻处理5 d时大豆分离蛋白的溶解性达到最低,仅为(47.62±1.04)%,冷冻处理后大豆分离蛋白溶液的浊度与冷冻处理时的溶液浓度和冷冻时间呈正比关系,当浓度为5%的大豆分离蛋白溶液经冷冻处理后,蛋白溶液浊度达到最高0.79;随着大豆分离蛋白溶液浓度的增加,冷冻处理后蛋白中二硫键的含量也随之增加,当大豆分离蛋白溶液浓度为6%时,冷冻处理后蛋白中二硫键含量最大值为(26.54±0.78)μmol/g;随着冷冻诱导程度的加深,蛋白的溶解性降低,浊度变高,蛋白质发生聚集,导致其微观结构由稀疏到致密,变得更加稳定。     

天然大豆分离蛋白稳定高内相乳液的制备及表征

本研究以天然大豆分离蛋白(SPI)为原料,探究了其稳定高内相乳液(HIPEs)的基本性质。对SPI的SDS-PAGE电泳、平均粒径,ζ电位进行表征与测定,探讨了蛋白浓度对稳定HIPEs显微结构、油滴粒径及流变性质的影响。结果表明:实验室制备SPI颗粒性质优良,为天然低变性率SPI。新鲜制备的HIPEs呈凝胶状,将其放置在室温下储藏6个月后仍保持稳定,稳定性优于牛血清白蛋白(BSA)及酪蛋白酸钠(SC)稳定的HIPEs。显微结构图表明其内部存在紧密堆积的网络结构。蛋白浓度为1.0 wt%时,SPI稳定HIPEs的最高油相体积分数为0.87。油相体积分数为0.8时,SPI稳定HIPEs的最低蛋白浓度为0.6 wt%。流变性质表明HIPEs内部存在以弹性为主的凝胶网络结构,随着蛋白浓度的增大,油滴粒径逐渐减小且呈均匀分布,粘弹性能逐渐增大。本研究对于开发新型高脂健康食品提供了新思路。     

UNIAXIAL COMPRESSION OF GELS MADE FROM PROTEIN AND K-CARRAGEENAN

Investigations of gels (18% total solids) made from pea protein isolates (PPI) or soy protein isolate (SPI) with differing amounts of _K-carrageenan added showed that the gel strength increased with the concentration of _K-carrageenan. When the concentration of_K-carrageenan exceeded 0.4%, gels made with PPI were stronger and more stiff than equivalent gels made with SPI. Addition of _K-carrageenan stabilized gels made with PPI towards variations in brittleness (indicated by strain at fracture) with pH. This was not the case when SPI was used. Preheating (75C, 2 min) suspensions containing protein isolates and _K-carrageenan before gel formation increased the strength and stiffness of the final gels, most pronounced when SPI was used. Addition of NaCl (0.5–2%) reduced strength and stiffness of gels, whereas CaCl₂ had no influence on gel properties. Mixtures of PPI and SPI proved to be weaker and more brittle than gels made from only SPI of PPI. Results indicate that using proteins of different origin can cause differences in gel structure.     

猪肉乳化香肠中大豆分离蛋白的检测

通过聚丙烯酰胺凝胶电泳法(sodium dodecyl sulfate polyacrylamide gel electrophoresis,SDS-PAGE)电泳检测猪肉乳化香肠中的大豆分离蛋白(soybean protein isolate,SPI)。结果显示,大豆蛋白主要有5条蛋白条带(β-大豆伴球蛋白中的d1、α'、β、d2亚基和大豆球蛋白的d3亚基) 能和猪肉的蛋白条带区分开;其中,获得了由α'亚基蛋白条带的光强度值与SPI质量分数计算得到的一个线性回归方程,该方程作为检测猪肉乳化香肠中SPI添加量(0.5%～10%)的标准曲线。应用得到的标准曲线预测已知SPI质量分数(7%、3%、1.5%、0.8%、0.5%)的猪肉乳化香肠,结果证明该方法具有很好的重复性(变异系数1.90%～7.01%)。同时将SPI质量分数的预测值和真实值进行线性回归分析,得到相关系数为0.98,证明了这种检测方法能应用于猪肉乳化香肠中大豆分离蛋白的定量检测。     

Molecular interactions and functionality of a cold-gelling soy protein isolate

ABSTRACT:  A soy protein isolate (SPI) was thermally denatured at a critical concentration of 8% protein for 3 h at 95 °C, resulting in a powder that was readily reconstituted at ambient temperature and that demonstrated improved heat stability and cold-set gel functionality when compared to a control SPI. When SPI was heated at 3% protein equivalently, prior to reconstitution to 8% protein, the final viscosity was about 3 orders of magnitude less than the original sample. The viscosity of SPI heated at 3% protein was still nearly 2 orders of magnitude less than the original sample after both samples were reheated at 8% protein. These results suggested that heat denaturation at low protein concentrations limited network formation even after the protein concentration and interaction sites increased, impacting the isolate's cold gelling ability. Gelation was prevented upon treatment of SPI with iodoacetamide, which carbaminomethylated the cysteine residues, establishing the role of disulfide bonds in network formation. The viscosity of the 8% protein dispersion was also reduced by 2 orders of magnitude when treated with 8 M urea, and when combined with 10 mM DTT the gel viscosity was decreased by another order of magnitude. These results suggested that hydrophobic interactions played a primary role in gel strength after disulfide bonds form. The need for a higher concentration of protein during the heating step indicated that the critical disulfide bonds are intermolecular. Ultimately, the functionality produced by these protein–protein interactions produced a powdered soy protein isolate ingredient with consistent cold-set and thermal gelation properties.