转谷氨酰胺酶催化大豆蛋白和乳清蛋白合成耐热性聚合蛋白

用商品级转谷氨酰胺酶(TG-B)聚合大豆蛋白和乳清蛋白形成高耐热、耐酸的蛋白聚合物。蛋白聚合物的合成量由SDS-PAGE电泳结合凝胶成像分析测定;蛋白聚合物的耐热性用差示扫描量热法(DSC)测定;蛋白聚合物的酸溶解性用双缩脲法测定。结果表明TG-B聚合大豆蛋白和乳清蛋白形成的蛋白聚合物的最适条件为pH为6～7;反应温度30℃～45℃,反应时间4h,加酶量为6当量单位/g蛋白,在此条件下蛋白聚合物的转化量可达30%,所合成蛋白聚合物可耐130℃的热处理而不发生变性;并在pH3.2～4.3范围不发生沉淀。     

微生物转谷氨酰胺酶催化乳清蛋白聚合研究

采用SDS－PAGE分析，研究了不同条件下微生物转谷氨酰胺酶（MTGase）催化乳清蛋白（WPI）聚合。结果显示，MTGase可催化乳清蛋白的β－乳球蛋白（β-LG）和α－乳清蛋白（α－LA）聚合，形成低聚物或生物聚合物，其中β-LG更易受MTGase的催化，当TGase酶浓度一定时（0.5U/mL),TGase催化WPI聚合的最佳底物质量分数范围为2％－4％，对WPI进行加热预处理，同时添加还原剂，可明显提高MTGase对WPI的催化活性，MTGase催化WIP的最适PH值范围为6．5－7．5，当WPI经预热处理（85℃，15min），同时添加20mmol/L的DTT，TGase催化WPI聚合12h，可使质量分数为92％的β-LG和质量分数为75％的α－LA聚合。     

超滤浓缩乳清蛋白并分离乳糖的研究

采用管式超滤装置,选用切割分子量为20000的聚丙烯腈膜,对乳清进行了超滤浓缩试验。结果表明,降低乳清pH值可提高透液通量,把乳清调整至pH7．0,再离心除去不溶性钙盐,可获得最大透液透量。中性乳清经离心沉降后,在进口压力0.24MPa,温度45℃条件下浓缩180min,平均透液通量达到29．1kg／m2·h,蛋白质含量提高到2.85％,透过液中乳糖浓度变化不大。     

超滤分离大豆乳清蛋白的研究

就超滤分离大豆乳清蛋白的意义,分离工艺、膜与组件的评价、操作参数的影响与优选、膜清洗工艺及浓缩液的应用作了全面介绍和论述,为提高原料利用率,减轻乳清废液对城市环境的污染,提供了一条切实可行的新途径。     

转谷氨酰胺酶催化大豆蛋白和乳清蛋白合成耐热性聚合蛋白

用商品级转谷氨酰胺酶 (TG- B)聚合大豆蛋白和乳清蛋白形成高耐热、耐酸的蛋白聚合物。方法 :蛋白聚合物的合成量由 SDS- PAGE电泳结合凝胶成像分析测定 ;蛋白聚合物的耐热性用差示扫描量热法 (DSC)测定 ;蛋白聚合物的酸溶解性用双缩脲法测定。结果 :TG- B聚合大豆蛋白和乳清蛋白形成的蛋白聚合物的最适条件为 :p H为 6- 7;反应温度 30～ 45℃ ,反应时间 4h,加酶量为 6当量单位 / g蛋白 ,在此条件下蛋白聚合物的转化量可达 30 % ,所合成蛋白聚合物可耐 1 30℃的热处理而不发生变性 ;并在 p H3.2～ 4.3范围不发生沉淀。     

转谷氨酰胺酶催化大豆蛋白和乳清蛋白合成耐热性聚合蛋白

用商品级转谷氨酰胺酶 （TG- B）聚合大豆蛋白和乳清蛋白形成高耐热、耐酸的蛋白聚合物。方法 :蛋白聚合物的合成量由 SDS- PAGE电泳结合凝胶成像分析测定 ;蛋白聚合物的耐热性用差示扫描量热法 （DSC）测定 ;蛋白聚合物的酸溶解性用双缩脲法测定。结果 :TG- B聚合大豆蛋白和乳清蛋白形成的蛋白聚合物的最适条件为 :p H为 6- 7;反应温度 30～ 45℃ ,反应时间 4h,加酶量为 6当量单位 / g蛋白 ,在此条件下蛋白聚合物的转化量可达 30 % ,所合成蛋白聚合物可耐 1 30℃的热处理而不发生变性 ;并在 p H3.2～ 4.3范围不发生沉淀。      

超滤浓缩大豆乳清蛋白

本文对超滤技术在浓缩大豆乳清蛋白中的应用进行初步的探索,探索压力、温度、运行时间和浓缩倍率对浓缩大豆乳清蛋白的影响,结果表明截留率在92%以上。     

转谷氨酰胺酶聚合改性大豆分离蛋白的功能特性研究

研究了转谷氨酰胺酶(MTGase)聚合改性大豆分离蛋白的持水性、吸油性、溶解性、乳化性、发泡性及凝胶强度等功能特性。结果显示,与大豆分离蛋白相比,MTGase改性的大豆分离蛋白(MSPI)具有更高的凝胶性和乳化稳定性,但其溶解性、持水性、吸油性、起泡性与泡沫稳定性和乳化性明显减弱。     

转谷氨酰胺酶催催化大豆蛋白和乳清蛋白合成耐热性聚合蛋白注

用商品级转谷氨酰胺酶（TG－B）聚合物大豆蛋白和乳清蛋白形成高耐热,耐酸的蛋白聚合物,蛋白聚合物的合成量由SDS－PAGE电泳结合 胶成像分析测定,蛋白聚合物的耐热性用差示扫描量热法（DSC）测定,蛋白聚合物的酸溶解性用双缩脲法测定,结果表明TG－B聚合大豆蛋白和乳清蛋白形成的蛋白聚合物的最适条件为：pH为6－7,反应温度30℃－45℃,反应时间4h,加酶量为6当量单位／g蛋白,在此条件下蛋白聚合的转化量可达305,所合成蛋白聚合物可耐130℃的热处理而不发生变性,并在pH3.2-4.3范围不发生沉淀。     

Transglutaminase cross-linking to enhance elastic properties of soy protein hydrogels with intercalated montmorillonite nanoclay

To strengthen the network of bio-nanocomposite hydrogels, layered montmorillonite (MMT) nanoclay was intercalated by surface-coating with soy protein (SP) before mixing with 6% w/v SP for cross-linking by microbial transglutaminase (mTGase). Dynamic rheology was performed to study variables of NaCl and mTGase concentrations, with and without 1% w/v MMT. Without mTGase, the highest storage modulus (G′) was observed at 100 mM for samples without MMT, which was twice of the highest G′ for samples with MMT, at 200 mM NaCl. With mTGase, a shorter gelation time and a stronger hydrogel were observed at a higher enzyme level. Overall, the non-gelling 6% w/v SP dispersion was transformed to a hydrogel with G′ of 1099 Pa after addition of 100 mM NaCl and 1% SP-coated MMT and treatments by 6.25 U/g-protein mTGase for 2 h and heating/cooling steps. The integration of surface-coating and mTGase cross-linking is promising to improve properties of the nanocomposite system.     

Covalent attachment of fenugreek gum to soy whey protein isolate through natural Maillard reaction for improved emulsion stability

Soy whey protein isolate (SWPI)–fenugreek gum (hydrolyzed and unhydrolyzed) conjugates were prepared by Maillard-type reaction in a controlled dry state condition (60 °C, 75% relative humidity for 3 days) to improve emulsification properties. Fenugreek gum was partially hydrolyzed using 0.05 M HCl at 90 °C for 10 min (HD10), 30 min (HD30) and 50 min (HD50) to examine if molecular weight had an effect on the emulsifying properties. The formation of SWPI–fenugreek gum conjugates was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Measurements of particle size distribution and average particle size have shown that conjugation of SWPI–fenugreek gum at 60 °C for 3 days was enough to produce relatively small droplet sizes in oil-in-water (o/w) emulsions. A ratio of 1:3 and 1:5 of SWPI:fenugreek gum was more effective in stabilizing emulsion compared to 1:1 ratio. Unhydrolyzed fenugreek gum conjugates exhibited better emulsifying properties compared to partially hydrolyzed fenugreek gum conjugates. The order of the conjugates in lowering the particle size of emulsions was as follows: SWPI–unhydrolzed fenugreek gum > SWPI–HD10 > SWPI–HD30 > SWPI–HD50.     

大豆乳清蛋白的胰蛋白酶改性研究

大豆乳清蛋白虽然具有一些较好的功能特性,但由于其主要组分胰蛋白酶抑制剂存在热稳定性差,抑制血清中胰蛋白酶的活性等缺点。采用相应的改性技术对超滤提取的大豆乳清蛋白进行了胰蛋白酶改性研究,确定的改性条件为:底物浓度2%,酶用量3500 U/100 g蛋白,水解时间3h,水解温度60℃。改性后的大豆乳清蛋白起泡性和乳化稳定性、NSI值、相对抗氧化能力均得到提高,分别提高108.33%、6.29%、0.96%、23.15%。     

Thermal stability of soy protein isolate and hydrolysate ingredients

The objective of this study was to characterize the effects of pH, protein concentration and calcium supplementation on thermal stability, at 140 °C, of soy protein isolate (SPI) and soy protein hydrolysate (SPH) ingredients. Increasing pH between 6.4 and 7.5 led to significantly (p < 0.05) higher mean heat coagulation times (HCTs) at 140 °C, for all soy protein ingredients at 1.8, and 3.6% (w/v) protein. Increasing protein concentration from 1.8 to 7.2% (w/v) led to shorter HCTs for protein dispersions. Calcium supplementation up to 850 mg/L, except in the case of supplementation of SPI 1 with calcium citrate (CaCit), decreased HCT for soy protein ingredient dispersions, at pH 6.4 – 7.5. No significant differences (p < 0.05) were found in mean HCT for dispersions supplemented with calcium chloride (CaCl₂) and those supplemented with CaCit at 450, 650 and 850 mg/L Ca²⁺, in the pH range 6.4–7.5.     

大豆乳清蛋白乳化性的研究

对大豆乳清蛋白的乳化性进行了研究,并与大豆分离蛋白进行了比较。研究结果表明,大豆乳清蛋白的乳化稳定性优于大豆分离蛋白,乳化能力与大豆分离蛋白基本相当。正交实验确定大豆乳清蛋白乳化稳定性效果最优条件是:浓度20%、温度40℃、pH值9、时间25min。大豆乳清蛋白的乳化性的最佳条件是:浓度25%、温度40℃、pH值9、时间25min。离子对大豆乳清蛋白乳化性和乳化稳定性的影响为钠离子>钾离子,且钠离子的作用明显,使用大豆乳清蛋白乳化稳定性功能时选用离子条件是钠离子0.01mol/L,使用大豆乳清蛋白乳化性功能时选用离子条件是钠离子0.05mol/L。     

Enhancing the adsorption of the proteins in the soy whey wastewater using foam separation column fitted with internal baffles

In order to promote industrialization of protein recovery from soy whey wastewater using foam separation, a novel foam separation column fitted with baffles consisting of circular disk segments placed at regular intervals in the liquid layer of the column (known as CIB in this paper) was developed to intensify the interfacial adsorption of the proteins. The column was evaluated by studying the effects of: 1. volumetric air flow rate, 2. the initial concentration of the proteins in the soy whey water, 3. the size and spacing of the disk segments on protein adsorption characteristics. The results showed that such a column could significantly intensify the adsorption of proteins. The maximum surface excess was obtained at a volumetric air flow rate of 250 mL/min, a baffle spacing of 10 mm and a disk segment chord length of 29.8 mm. At an initial concentration of the proteins of 1.8 g/L, the surface excess given by the baffled foam column was 193% higher than that given by an unbaffled column.     

Hydrolysis of whey protein isolate using subcritical water

Hydrolyzed whey protein isolate (WPI) is used in the food industry for protein enrichment and modification of functional properties. The purpose of the study was to determine the feasibility of subcritical water hydrolysis (SWH) on WPI and to determine the temperature and reaction time effects on the degree of hydrolysis (DH) and the production of peptides and free amino acids (AAs). Effects of temperature (150 to 320 °C) and time (0 to 20 min) were initially studied with a central composite rotatable design followed by a completely randomized factorial design with temperature (250 and 300 °C) and time (0 to 50 min) as factors. SWH was conducted in an electrically heated, 100-mL batch, high pressure vessel. The DH was determined by a spectrophotometric method after derivatization. The peptide molecular weights (MWs) were analyzed by gel electrophoresis and mass spectrometry, and AAs were quantified by high-performance liquid chromotography. An interaction of temperature and time significantly affected the DH and AA concentration. As the DH increased, the accumulation of lower MW peptides also increased following SWH (and above 10% DH, the majority of peptides were <1000 Da). Hydrolysis at 300 °C for 40 min generated the highest total AA concentration, especially of lysine (8.894 mg/g WPI). Therefore, WPI was successfully hydrolyzed by subcritical water, and with adjustment of treatment parameters there is reasonable control of the end-products.