氧化海藻酸钠改性大豆蛋白胶黏剂制备与性能研究

利用氧化海藻酸钠改性大豆蛋白胶黏剂,采用X射线晶体衍射(XRD)、全反射傅里叶变换红外光谱(ATR-FTIR)对胶黏剂进行表征,对其黏度、吸湿率和残留率等性能进行研究。结果表明,氧化海藻酸钠改性大豆蛋白胶黏剂黏度有所改善,吸湿率降低4.3%,残留率增加11.9%。     

木素用于酚醛树脂胶黏剂改性

采用酸析法回收得到的木素为原料,替代部分苯酚与甲醛反应制备木素改性酚醛树脂胶黏剂,并测定其固含量、动力黏度(40℃)、游离甲醛含量和胶合强度等性能。主要考察了木素/酚化木素掺入比例、催化剂(碱)种类及用量、酚醛摩尔比以及反应温度对胶黏剂性能的影响。结果表明,合成木素酚醛树脂胶黏剂较佳的工艺条件为:木素掺入比例5%～15%(质量百分数,以苯酚质量为基准),酚醛摩尔比1:1.5,催化剂为NaOH,加入量0.6%(质量百分数,以苯酚质量为基准),反应时间3h。采用酚化木素时,掺入比例可达45%,制得胶黏剂性能优于纯木素。木素替代部分苯酚改性酚醛树脂胶黏剂,不仅可以降低生产成本,而且更环保。     

制浆黑液在酚醛树脂胶黏剂中的应用

制浆黑液中的降解木质素含有酚羟基结构,可以替代部分苯酚制备酚醛树脂.以NaOH为催化剂,采用二次缩聚法制取酚醛树脂胶黏剂.实验表明,当黑液添加量为15%时,胶黏剂的黏度比空白实验增加1倍,游离甲醛含量降低了27%,胶合强度提高了13.2%.红外光谱分析表明,黑液中的木质素与游离甲醛反应生成有羟甲基的物质,该物质能与酚醛树脂胶粘剂中的物质发生反应,从而既降低了甲醛含量又提高了胶黏剂的胶合强度.     

基于尿素和STP控制修饰的大豆分离蛋白胶黏特性的研究

采用尿素和磷酸化试剂共同修饰大豆分离蛋白(SPI),主要研究不同浓度的多聚磷酸钠(STP)对经尿素控制变性后SPI胶黏强度、耐水性和二级结构的影响。先将SPI添加到3 mol/L尿素溶液中,SPI发生部分变性,然后再加入浓度为0、2%、5%、8%、10%的STP,对SPI进行磷酸化控制修饰。结果表明,STP浓度越大,其黏度越高。将经控制修饰的SPI应用在樱桃木、水曲柳和松木上的黏接后发现,STP能够提高胶黏强度和耐水性,当STP的浓度为5%时,其胶黏强度和耐水性达到最大值。SPI的圆二色性光谱图分析表明,磷酸化修饰后,SPI二级结构中的无规卷曲含量显著增加。对尿素和STP控制修饰SPI分子并提高其胶黏特性的机理也进行了探索。     

碱处理对油茶籽蛋白降解及其胶黏剂性能的影响

为了促进油茶产业的发展以及开发新的蛋白胶黏剂,以油茶籽蛋白为原料（蛋白质含量36%,纤维含量15%）,采用碱（NaOH）对其进行降解处理,并与交联剂混合作为胶黏剂应用于胶合板的热压中。考察了NaOH加量对油茶籽蛋白水解度和降解液甲醛反应能力、黏度和胶黏剂胶合性能的影响,并对降解前后油茶籽蛋白进行了红外表征。结果表明：NaOH可使油茶籽蛋白有效降解,并产生活性基团和活性点;随着NaOH加量的增加,油茶籽蛋白水解度和降解液甲醛反应能力呈先急剧增加后缓慢增加的趋势,降解液黏度呈先增加后急剧减小再缓慢减小的趋势;所制备的胶合板的湿状胶合强度总体呈先增加后减小的变化趋势。NaOH加量为7%时,油茶籽蛋白降解液具有较高的反应活性、较大的内聚强度、较好的施胶性能和优良的胶合性能。     

SDS改性大豆分离蛋白胶粘剂的性能研究

采用碱溶酸沉法从低温脱脂大豆粉中提取大豆分离蛋白(SPI),应用十二烷基硫酸钠(SDS)对SPI进行化学改性,研究不同浓度的SDS溶液对改性SPI胶粘剂的热性能、流变性能以及粘接性能的影响.结果表明,随着SDS浓度的增加,改性SPI胶粘剂的变性温度及变性焓均有下降,表观黏度随着SDS浓度的增加而增大.SDS改性显著提高了SPI胶粘剂在木片胶合中的粘接性能、耐候性能和耐水性能,当改性试剂SDS浓度为1.0%时,其性能最佳.     

尿素改性制备芝麻蛋白胶黏剂的研究

以芝麻蛋白为原料,用尿素改性制备芝麻蛋白胶黏剂。以尿素浓度、料液比、反应时间、反应温度进行单因素试验,研究其对芝麻蛋白胶黏剂表观黏度、胶合强度的影响。通过正交试验进行优化,得出最佳制备工艺条件为:尿素浓度3 mol/L,料液比1∶8,反应时间4 h,反应温度25℃。在最佳条件下,芝麻蛋白胶黏剂的湿胶合强度为0.78 MPa,满足国家标准Ⅱ类(≥0.70 MPa)胶合板的要求。     

微波处理对豆粕胶黏剂性能影响的研究

采用微波对豆粕粉进行处理制备胶合性能良好的豆粕胶黏剂,通过单因素试验探究微波功率、微波时间、豆粕粉质量分数对胶黏剂的黏度、干剪切强度和固形物含量的影响,并通过正交试验确定微波处理豆粕粉制备胶黏剂的最佳工艺条件,采用傅里叶红外光谱(FT-IR)、扫描电子显微镜探究微波处理对大豆蛋白分子结构和形态的影响。结果表明:微波处理豆粕粉使其中的大豆蛋白分子结构遭到破坏,暴露出内部的极性与非极性基团,暴露的基团通过氢键、静电相互作用等形成分子聚集体,增加了胶合强度;同时得到微波处理豆粕粉制备胶黏剂的最佳工艺条件为微波功率300 W、微波时间3 min、豆粕粉质量分数25%,在此条件下豆粕胶黏剂的干剪切强度为1. 61 MPa、黏度为924 MPa·s、固形物含量23. 05%。     

多糖类稳泡剂对大豆分离蛋白起泡性的影响

探讨了黄原胶等稳泡剂对大豆分离蛋白(SPI)起泡性的影响。黄原胶等稳泡剂可能是由于增加了连续相黏度,继而起到了稳泡作用;而由于热处理能够使蛋白质分子表面暴露的疏水性氨基酸残基增加,从而提高了起泡能力。通过响应面(RSM)分析实验,得出改善SPI起泡特性的最佳工艺条件:加热温度67℃,加热时间18 min,蛋白质浓度3.29(W/V),黄原胶添加量0.13(W/V),搅打时间4.56 min。将最终得到的SPI泡沫与蛋清白泡沫比较,发现二者具有类似的黏性和硬度,且在气泡大小和形状上也较为相近。     

碱木素／尿醛树脂胶黏剂的合成研究

利用制浆黑液中的碱木素为主要原料,经过羟甲基化改性,甲醛缩合制备纤维板胶黏剂,探索改性木素胶黏剂粘结效果。用正交试验方案设计对碱木素改性、胶黏剂制备工艺进行优化。研究表明：将碱木素进行羟甲基化改性,其活性明显提高。最佳的优化条件：甲醛用量7mmol·g-llignin,pH值10,反应温度70℃,反应时间120min;改性碱木素最佳的加入量比例为20％。用碱木素制备改性木素胶黏剂可利用造纸黑液木素资源,而且具有广泛的应用前景。     

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.     

Modified soy protein isolate with improved gelling stability by glycosylation under the conditions of ocean shipping

In this study, we modified the soy protein isolate (SPI) by glycosylation technology, tracked and detected its gelling properties in a trial‐box, which simulated the ocean shipping environment, then determined the optimised parameters for glycosylation modification, including humidity, temperature, reaction time, and the amount of polysaccharide added. The gelling stability of the glycosylated SPI increased significantly compared with the non‐modified SPI. The physicochemical properties of glycosylated SPI and non‐modified SPI (degree of glycosylation and sulfhydryl groups) were measured to correlate their effects on the gel strength of glycosylated SPI gels. With an analysis of gel microstructure images measured by a scanning electron microscope, we further verified the formation of the macromolecular complex in glycosylated SPI during glycosylation; the microscopy also revealed a relationship between microstructure and gelling properties of SPI.     

Development of biodegradable hot-melt adhesive based on poly-ε-caprolactone and soy protein isolate for food packaging system

A biodegradable hot-melt adhesive was developed from poly-ε-caprolactone (PCL) and soy protein isolate (SPI). PCL and SPI were mixed at varying ratios with plasticizers (coconut oil and PEG400). Thermal properties of PCL:SPI hot-melt adhesive were characterized with a differential scanning calorimeter (DSC) and softening point measurement. The surface morphology of PCL:SPI blend was examined by scanning electron microscopy (SEM). Tensile strength and elongation of PCL:SPI hot-melt adhesive films were measured using Instron testing machine. Lap shear strength of PCL:SPI hot-melt adhesives on medium density fiberboard was determined according to TAPPI UM633 method. The melting point and crystallinity of PCL in the blends decreased as the SPI content increased. The softening points of PCL:SPI hot-melt adhesive were about 59-75 °C. As the SPI concentration was increased, the tensile strength of its films decreased. The elongation of the PCL:SPI hot-melt adhesives varied with the type of plasticizer. Lap shear strength of PCL:SPI hot-melt adhesive was about 1.9 MPa.     

聚磷酸钠对大豆分离蛋白的修饰研究

采用多聚磷酸钠对大豆分离蛋白进行磷酸化修饰,研究磷酸化反应的工艺条件及改性后大豆分离蛋白几种功能特性的变化。结果表明:当大豆分离蛋白4%、三聚磷酸钠9%、反应初始pH9、反应时间3h时,磷酸化程度最大;磷酸化后的大豆分离蛋白的溶解性、乳化性以及粘度都有不同程度的改善。     

干热处理下焦磷酸钠改性大豆蛋白乳化和起泡性质研究

研究了在80℃干热条件下焦磷酸钠改性大豆蛋白的乳化和起泡性质。研究发现:改性大豆蛋白的乳化性质和起泡性质得到明显的改善,蛋白质结合磷的量随干热处理时间的延长而增加。在干热处理前对大豆蛋白进行适度的预热处理大大提高了蛋白质结合磷的量,80℃预热处理10min使改性大豆蛋白表现出最好的乳化性质,而预热处理20min的改性蛋白质却表现出最好的起泡性质。红外光谱分析发现,焦磷酸钠以磷酸根的形式与蛋白质分子的游离羟基缩合。SDS-凝胶电泳表明,焦磷酸钠能抑制干热处理时大豆蛋白各亚基之间的聚合作用,从而提高其功能性质。该研究为大豆蛋白的改性提供了新的思路。     

葡聚糖接枝对大豆蛋白功能特性及结构的影响

采用干热糖基化对大豆分离蛋白进行改性,研究其功能特质及结构特性。以葡聚糖和大豆分离蛋白(soy protein isolate,SPI)为原料,考察底物质量比和反应时间两个因素。结果表明:蛋白质与糖质量比2∶1,反应温度60℃时,产物接枝比较高,褐变程度中等;与SPI相比,糖基化之后大豆蛋白的溶解度提高了72.72%,乳化活性(emulsifying activity,EAI)和乳化稳定性(emulsion stability,ESI)分别提高了117.53%和134.20%。十二烷基硫酸钠聚丙烯酰胺凝胶电泳(sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE)表明SPI与葡聚糖发生了糖基化反应;傅里叶红外光谱(Fourier transform infrared spectroscopy,FT-IR)和荧光光谱分析表明,糖链的引入导致了大豆蛋白空间结构的变化;模拟体外消化特性结果表明,葡聚糖糖基化修饰对SPI体外消化性的改善效果不明显。     

Physicochemical and Functional Properties of Soy Protein Substrates Modified by Low Levels of Protease Hydrolysis

ABSTRACT: Endo-protease treatments achieving low degrees of hydrolysis (DH 2% and 4%) were used to improve functional properties of hexane-extracted soy flour (HESF), extruded-expelled partially defatted soy flour (EESF), ethanol-washed soy protein concentrate (SPC), and soy protein isolate (SPI). These substrates had protein dispersibility indices ranging from 11% to 89%. Functional properties, including solubility profile (pH 3 to 7), emul-sification capacity and stability, foaming capacity and stability, and apparent viscosity were determined and related to surface hydrophobicity and peptide profiles of the hydrolysates. Protein solubilities of all substrates increased as DH increased. Emulsification capacity and hydrophobicity values of the enzyme-modified HESF and EESF decreased after hydrolysis, whereas these values increased for SPC and SPI. Emulsion stability was improved for all 4% DH hydrolysates. Hydrolyzed SPC had lower foaming capacity and stability. For substrates other than SPC, foaming properties were different depending on DH. Hydrolysis significantly decreased the apparent viscosities regardless of substrate. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated differences in the molecular weight profiles of the hydrolysates. HESF and EESF, which had high proportions of native-state proteins, showed minor changes in the peptide profile due to hydrolysis compared with SPC and SPI.     

The impact of anthocyanin-rich red raspberry extract (ARRE) on the properties of edible soy protein isolate (SPI) films

To modify the properties of edible soy protein isolate (SPI) films, 0.5% anthocyanin-rich red raspberry (Rubus strigosus) extract (ARRE) (0.5 g raspberry powder in 95% ethyl alcohol/water/85% lactic acid [80:19:1. v/v/v]) was incorporated into film-forming solutions. ARRE resulted in an SPI film having significantly enhanced tensile strength (P < 0.05) and % elongation at break (P < 0.05), as well as increased water swelling ratio (P < 0.05) and in vitro pepsin digestibility (P < 0.05). The resultant films also showed significantly decreased water solubility and water vapor permeability (P < 0.05). In addition, ARRE increased darkness, redness, and yellowness film appearance as evidenced by a lower L* (P < 0.05), greater positive a* (P < 0.05), and a higher b* (P < 0.05) than the control film. Scanning electron microscopy images revealed that extract-added films had denser and more compact cross-section microstructure. Fourier transform infrared spectra illustrated that ARRE-created hydrogen bonding involved conformational changes of soy protein without destroying its backbone structure. SDS-PAGE electrophoretograms revealed that the extract induced intermolecular interaction of the soy protein monomers. Natural plant extracts would be a promising ingredient to make SPI films with different physicochemical properties and applications. PRACTICAL APPLICATION: This study characterizes the potential physicochemical changes of SPI film with incorporated raspberry extract. Upon the above modification, the resultant film was found to enhance the applications of pure SPI film in food packaging. For example, SPI-ARRE film could prolong the usage life of SPI film due to increased strength, or could be useful as a desiccant (drying agent) such as a water-absorbing sheet for preserving dried foods due to its increased hydrophilic surface and water-swelling ratio. SPI-ARRE film could also be alternately used as a food wrap with unique color.     

Development of a probiotic delivery system from agrowastes, soy protein isolate, and microbial transglutaminase

Abstract: Probiotic delivery system was developed via the use of microbial transglutaminase (MTG) cross‐linked soy protein isolate (SPI) incorporated with agrowastes such as banana peel (BE), banana pulp (BU), and pomelo rind (PR). Inoculums of Lactobacillus bulgaricus FTDC 1511 were added to the cross‐linked protein matrix. The incorporation of agrowastes had significantly (P < 0.05) reduced the strength, pH value, and the lightness of the SPI gel carriers, while sodium dodecyl sulfate‐polyacrylamide gel electrophoresis profiles revealed that the occurring cross‐links within the SPI gel carriers were attributed to the addition of MTG. Scanning electron microscope micrographs illustrated that SPI carriers containing agrowastes have exhibited a less‐dense protein matrix. All the SPI carriers possessed maximum swelling ratio at 4 to 4.5 within 15 min in simulated gastric fluid (SGF), whereas the maximum swelling ratios of SPI/BE, SPI/BU, and SPI/PR were higher compared to that of control in simulated intestinal fluid (SIF). Additionally, SPI carriers in SGF medium did not show degradation of structure, whereas a major collapse of network was observed in SIF medium, indicating controlled‐release in the intestines. The addition of agrowastes into SPI carriers led to a significantly (P < 0.0001) lower release of L. bulgaricus FTDC 1511 in SGF medium and a higher release in SIF medium, compared to that of the control. SPI carriers containing agrowastes may be useful transports for living probiotic cells through the stomach prior to delivery in the lower intestines. Practical Application: Agrowastes could be utilized as a new probiotic carrier for enhanced gastrointestinal transit and during storage. This also reduces the amount of agrowastes accumulated.