转谷氨酰胺酶对荞麦蛋白功能特性的影响

微生物转谷氨酰胺酶(MTGase)能够使荞麦蛋白(BWP)的大部分球蛋白亚基被聚合,而几乎不能使分子量低于36kDa的碱性亚基聚合。BWP聚合物(催化时间<60min)的溶解度(PS)较BWP显著增加,聚合物的PS随反应时间的延长而降低;MTGase催化BWP反应120min可明显降低其PS(P<0.05)。聚合反应能提高BWP的持水能力(WH)和持油能力(FA),且BWP聚合物的FA随反应时间的增加而增强。适当的交联会使BWP的起泡性能增加,但继续提高交联度(延长酶反应时间),BWP的起泡性能反而降低。BWP聚合物的乳化活性指数(EAI)降低,乳化液稳定性(ES)却增强。     

加工工艺对荞麦蛋白热性质和体外模拟消化过程的影响

本实验研究了加工工艺对荞麦蛋白(BWP)的热性质和体外模拟消化过程的影响。荞麦蛋白有两个变性温度,在80℃和102℃附近,分别对应8S和13S球蛋白的变性。脂肪的存在对荞麦蛋白的变性温度影响不大,但会降低其热焓。在模拟的胃蛋白酶消化过程中,BWP的氮释放量较大豆分离蛋白(SPI)先高后低;而在胰蛋白酶消化过程中,BWP的氮释放量较SPI高。这与其蛋白组成以及SPI中存在活性较高的胰蛋白酶抑制剂有关。荞麦蛋白的球蛋白(13S和8S)易被降解(胃蛋白酶消化阶段),而2S清蛋白的降解主要集中在胰蛋白酶消化阶段。经脱脂处理、超声协助提取的荞麦蛋白(DFU-BWP)和搅拌提取的荞麦蛋白(FM-BWP)的氮释放量在整个胃蛋白酶消化过程中类似,均明显高于超声提取的荞麦蛋白(FU-BWP)(p<0.05),说明胃蛋白酶对BWP的降解过程与其脂肪含量以及加工工艺有关。     

脱脂麦胚蛋白功能特性的研究

中国农业大学食品学院郑如力等以脱脂麦胚蛋白为材料,研究了其溶解性、乳化性、起泡性和持水性等功能特性。结果表明：脱脂麦胚蛋白的等电点为4.0,pH＞6.0时蛋白质溶解指数NSI值可达70％,具有较高的溶解度;脱脂麦胚蛋白的乳化活性(EA)和乳化稳定性(ES)与牛血清白蛋白近似,并略高于酪蛋白;脱脂麦胚蛋白具有很好的起泡性(FC),其泡沫稳定性(FS)稍差,但可通过物理、化学或酶处理方法来克服;脱脂麦胚蛋白具有非常理想的持水性(WR),在pH=8.0和70 ℃时有最高持水性。 (摘自G.O.S.2000-10-01)     

脱脂麦胚蛋白的制取和理化及其功能特性的研究

本文用碱提取后等电点沉淀法制取了脱脂麦胚蛋白 ,并对其理化和功能特性进行了研究。结果表明 :脱脂麦胚蛋白氨基酸含量高达 2 6 .793g/ 10 0g ,且种类齐全 ,八种必需氨基酸含量均较高 ;脱脂麦胚蛋白的等电点为 4 .0 ,pH >6 .0时蛋白质溶解指数NSI值可达 70 % ,具有较高的溶解度 ;脱脂麦胚蛋白的乳化活性EA和乳化稳定性ES与牛血清白蛋白近似 ,并略高于酪蛋白 ;脱脂麦胚蛋白具有很好的起泡性FC ,其泡沫稳定性FS稍差 ,但可通过物理、化学或酶处理方法来克服 ;脱脂麦胚蛋白具有非常理想的持水性WR ,在pH=8.0和温度 70℃时有最高持水性。     

酰化对大豆分离蛋白乳化性能的影响

目的:研究化学改性对大豆分离蛋白(SPI)乳化性能的影响;方法:采用乙酸酐和琥珀酸酐对SPI进行化学改性;结果:随酰化试剂用量的增大,酰化程度不断提高,在相同酰化试剂用量的条件下,乙酰化程度高于琥珀酰化.SPI的乳化活性指数(EAI)和乳化稳定性(ES)都随酰化程度的增大而增大.在中性和弱碱性(pH 5.0～9.0)范围内,酰化明显提高了SPI的EAI和ES.琥珀酰化的改性效果优于乙酰化;不过离子强度削弱了SPI的EAI和Es;结论:酰化可有效提高SPI的乳化性能,其中琥珀酰化的改性效果优于乙酰化.     

银杏蛋白功能特性研究

以大豆分离蛋白为对照,对银杏蛋白的功能特性进行研究。结果表明:银杏蛋白的等电点(pI)为4.4,高于大豆分离蛋白(pI4.0)。银杏蛋白的溶解度低于大豆分离蛋白。在试验条件下,银杏蛋白具有较好的起泡性(FC)、乳化性(EAI)与乳化稳定性(ES),但泡沫稳定性(FS)较差。pH对银杏蛋白的溶解度、FC、FS、EAI影响较大,对ES影响较小;NaCl浓度对银杏蛋白EAI、ES影响较大,对溶解度、FC和FS影响较小;蔗糖浓度对银杏蛋白的溶解度、FS影响较大,对FC、EAI和ES影响较小。     

酱油渣中蛋白的乳化特性研究

对比分析了酱油渣中蛋白(SRP)、糖基化大豆分离蛋白(GSP)和大豆分离蛋白(SPI)的ξ-电位、疏水性以及乳化活性和乳化稳定性。发现SRP的总糖和蛋白含量比为1∶1.4,其中含有大量的糖蛋白;SRP疏水性是SPI的2.5倍。SRP等电点接近pH=3.5,在酸性环境下溶解性较好。在酸性、高盐环境下SRP乳化能力高于GSP和SPI,在pH=5时,SRP的乳化活性(EAI)是SPI的8.1倍,在NaCl浓度为0.3mol/L时,SRP的EAI是SPI的1.77倍。     

超声波协助提取荞麦蛋白的研究

本试验采用超声波技术从全荞麦粉中提取荞麦蛋白(BWP),分别研究了超声处理时间、频率以及溶液pH值、液料比和原料粒度对荞麦蛋白(BWP)提取率的影响。结果表明最佳提取条件为溶液pH8.0,超声处理时间15min,超声频率15KHz,液料比20:1(mL:g),BWP提取率可达75%以上,产品纯度为77.33%。     

罗非鱼蛋白-大豆蛋白共沉淀物的乳化性

为研究罗非鱼蛋白-大豆蛋白共沉淀物的乳化性,以罗非鱼肉和脱脂豆粕为原料,按照不同质量比(1∶0、1∶1、2∶1、3∶1、0∶1)混合,采用碱溶酸沉法制备鱼分离蛋白(FPI)、罗非鱼蛋白-大豆蛋白共沉淀物(Co-p)和大豆分离蛋白(SPI),并探讨了p H、盐浓度、多糖对其乳化活性(EAI)和乳化稳定性(ESI)的影响。结果表明:FPI、Co-p(1∶1)、Co-p(2∶1)、Co-p(3∶1)和SPI的得率分别为62.21%、39.10%、29.58%、18.45%、32.10%(P0.05);p H 3.0时,FPI、Co-p和SPI的乳化活性依次减小,而p H 4.0~10.0时,Co-p(2∶1)和Co-p(3∶1)的乳化活性最好(P0.05);在0%~0.4%Na Cl体系中,Co-p的乳化活性明显强于FPI或SPI;p H 3.0~7.0时,添加0.2%~0.3%的瓜尔豆胶和黄原胶能显著提高蛋白乳化体系的EAI值(P0.05),且Co-p的乳化性较FPI或SPI有明显提高。比较而言,罗非鱼蛋白-大豆蛋白共沉淀物较FPI或SPI有更好的乳化性。     

桑叶蛋白的功能特性研究

采用超声波辅助提取结合盐酸沉析法提取桑叶蛋白,研究pH值、离子强度、蔗糖质量浓度和温度对桑叶蛋白功能特性的影响。结果表明：远离其等电点时,桑叶蛋白具有良好的持水性、溶解度、乳化性及乳化稳定性、起泡性;桑叶蛋白的持水性、溶解度和起泡性与NaCl浓度(0～1.0mol/L)呈正相关,而过高的离子强度(NaCl浓度高于0.6～0.8mol/L)会使桑叶蛋白的乳化性和乳化稳定性下降;蔗糖的加入会增加桑叶蛋白的持水性,但会降低其溶解度和起泡性,对桑叶蛋白的乳化性和乳化稳定性影响不大;桑叶蛋白的吸油性和起泡性与温度(4～80℃)呈正相关,持水性、溶解度、乳化性及乳化稳定性于60℃时最好。     

Functional properties of bovine blood plasma intended for use as a functional ingredient in human food

With the aim of using bovine blood as functional ingredient in food processing, as an emulsifier or fat replacer, a study of some functional properties of blood plasma was made. The effect of pH (3.0–8.0), tryptic hydrolysis and NaCl addition (0.034 mol/L) on the solubility, hydrophobicity and emulsifying properties of bovine blood plasma were studied. The results showed that the hydrophobicity and emulsifying activity index (EAI) of bovine blood plasma reached a maximum at pH 3.0 and 7.0, respectively, while the other parameters stayed nearly constant with pH change. Tryptic hydrolysis improved hydrophobicity at certain hydrolysis times, reduced solubility and emulsifying capacity (EC) and showed no effect on EAI and emulsion stability (ES). The influence of NaCl tested at pH 5.0 and 6.0 was only positive for plasma EAI at pH 5.0 and significantly reduced solubility, hydrophobicity and EC at pH 5.0 and 6.0. For ES, NaCl addition did not produce any modification.     

Study of Some Functional Properties of Casein: Effect of pH and Tryptic Hydrolysis

The trypsin was used to hydrolyze commercial casein at varied times and pH range. The functional properties studied were the emulsifying capacity (EC), the emulsifying activity index (EAI), and the emulsion stability (ES). The dispersed phase used was corn oil. The tryptic hydrolysis was beneficial to the solubility and EC of casein in practically all pH values and reaction times. In case of EAI, this same effect was less intense and was observed only in acid region (pH 3.0 to 5.0), while for ES the trypsin action was mainly deleterious in almost all pH range and reaction times.     

荞麦蛋白的功能特性研究

采用碱萃取酸沉析法提取制备了荞麦蛋白，并较为系统地研究了蛋白质浓度、温度、pH值、氯化钠和蔗糖对荞麦蛋白的三种功能特性（溶解性质、乳化特性和泡沫特性）的影响。结果表明，本实验条件下制备的荞麦蛋白具有优良的溶解性质，其乳化性质与对照样品大豆分离蛋白相当，但泡沫特性较差。     

Relationship between physicochemical and functional properties of amaranth (Amaranthus hypochondriacus) protein isolates

Protein isolates from six amaranth lines/cultivars (APIs) were evaluated to study their physicochemical (hunter colour, protein content and zeta potential), structural (thermal and conformational) and functional (emulsification, foaming, water and fat absorption) properties. APIs had protein content, whiteness index and gel temperature in range of 79.4–85.4%, 41.17–54.26 and 87.8–91.8 °C, respectively. The Fourier‐transform infrared spectra of APIs revealed α‐helix, β‐sheets and random coil conformations in the secondary structure. APIs with higher relative proportion of β‐sheets had higher Differential Scanning Calorimeter denaturation temperature and gel temperature. Minimum protein solubility (PS) was observed at pH 5.0, indicating isoelectric point (pI) of amaranth proteins. The PS, emulsifying activity index (EAI), emulsifying stability index (ESI), foaming capacity (FC) and foam stability (FS) of APIs at neutral pH were related to their zeta potential (ζ). The emulsifying and foaming properties were also determined at different pHs (between 2.0 and 9.0). The EAI‐pH profile of APIs confirmed close relationship between the emulsifying ability and PS.     

物理作用力对大豆分离蛋白乳化性及乳化稳定性的影响

研究物理作用力对4 种供试大豆分离蛋白乳化性及乳化稳定性的影响。分别采用不同浓度的NaCl、NaSCN、尿素和1,2- 丙二醇处理大豆分离蛋白以改变其物理作用力。研究结果表明：随着NaCl 和NaSCN 浓度的增加,乳化活性指数(EAI)值均呈先降低再升高的趋势,说明静电作用力起主导作用,疏水相互作用不利于乳化性。随着NaCl 和NaSCN 浓度的升高,乳化稳定性(ES)值均降低,说明静电作用力起主导作用,并且比疏水相互作用力的影响强。加入尿素可使蛋白质的疏水基团暴露出来,使EAI 值升高,但是加入不同浓度的尿素对乳化性的影响差别不大。EAI 值随着1,2- 丙二醇浓度的升高而升高,说明氢键相互作用利于乳化活性和乳化稳定性。     

Emulsifying properties of proteins extracted from Australian canola meal

Canola protein albumin fraction, globulin fraction, and canola protein isolate (CPI) were compared to commercial soy protein isolate (SPI) in terms of their emulsifying properties at various pH values. The globulin fraction had higher emulsifying capacity (EC), higher emulsifying activity index (EAI), and the droplet size of emulsions it stabilized was consistently smaller irrespective of pH compared to albumin fraction or CPI. In comparison to SPI, globulin fractions also had higher EC at all pH values tested, higher EAI at acidic pH, and smaller or comparable average emulsion droplet size at both pH 4 and 7. The stability of canola protein based emulsions were comparable to those of SPI based emulsions at most pH values (except the emulsion stabilized by the CPI at pH 4), with no significant (p > 0.05) changes in droplet size during storage for up to 7 days at room temperature. These emulsions, however, experienced separation into the emulsion and serum phases after 24 h storage at room temperature with the exception of CPI- and SPI-stabilized emulsions at pH 9. This study demonstrates the comparable emulsifying properties (forming or stabilizing) of some canola proteins to commercially available SPI, suggesting the potential use of canola proteins in food applications.     

木瓜蛋白酶控制水解蚕豆水溶性蛋白及水解度对蚕豆蛋白功能性质的影响

针对蚕豆蛋白在pH较低的体系中溶解性差、乳化能力低,制约其在食品工业中应用等问题,应用808Titrando瑞士万通全自动滴定仪控制木瓜蛋白酶水解蚕豆蛋白,实现蚕豆蛋白的有限水解,探讨水解度对蚕豆蛋白水解物的溶解性、乳化能力及持水性等功能性质的影响。通过木瓜蛋白酶的控制水解获得水解度为2%～4%的蚕豆蛋白水解物;与蚕豆蛋白相比,在pH4.0～6.0体系、水解度为4%的蚕豆蛋白水解物的溶解度提高2～3倍;pH6.0、水解度为2%的蚕豆蛋白水解物的乳化能力是蚕豆蛋白的2.3倍,持水力是蚕豆蛋白的1.6倍。     

植物球蛋白/姜黄素纳米复合物的制备及其对O/W型Pickering乳液氧化稳定性影响

本论文以两类植物球蛋白:豌豆分离蛋白(PPI)和大豆分离蛋白(SPI)为材料制备荷载姜黄素蛋白纳米复合物,并探究荷载前后蛋白所制备乳液的物理和氧化稳定性差异。结果表明:PPI和SPI在pH 3.0和pH 7.0下荷载前后蛋白纳米颗粒粒径没有明显变化。pH 7.0时两蛋白姜黄素荷载量均高于pH 3.0,各pH下SPI荷载量要高于PPI。表面疏水性的显著降低与荧光淬灭现象发生表明形成两种蛋白纳米复合物的主要作用力为疏水相互作用,同时在两pH下,PPI比SPI荧光蓝移趋势更明显且有效淬灭常数也更大,即更易形成复合物。与原蛋白相比,荷载后各蛋白颗粒所制备乳液乳化活性有少许降低,同时pH 3.0时各蛋白颗粒乳化活性要高于pH 7.0。各乳液生成初级氧化产物脂质氢过氧化物浓度的变化趋势与生成次级氧化产物TBARS相类似,均为荷载姜黄素后各乳液氧化水平加速,同时pH 3.0时各类型乳液油滴氧化程度均高于pH 7.0。     

Solubility and Emulsifying Properties of Soy Protein Isolates Modified by Pancreatin

Soy protein isolates (SPI) with varying degrees of hydrolysis (DH of 7, 11, 15, 17%) were produced using pancreatin. The surface hydrophobicity indices of pancreatin hydrolyzed SPI (PSPI) (34.5, 34.9, 39. 1, and 40.7 for 7, 11, 15, 17% DH, respectively) were higher than that of SPI (10.5) and control SPI (CSPI) (12.5, 11.9, 12.9, and 12.6 for 10, 60, 120, and 180 min incubation, respectively). The solubilities of PSPI at pH 4.5 were 2.7, 9.1, 11.9, and 18.7%, for 7, 11, 15, and 17% DH, respectively, while the solubilities of SPI and CSPI at the same pH were about 1. 6%. Solubilities of PSPI at pH 7. 0 were > 90% for all DHs tested, while those of SPI and CSPI were 85%. The emulsifying activity index (EAI) of PSPI increased with increasing DH. PSPI with 15% DH had highest EAI (1. 122) which was higher (P < 0. 05) than those of SPI (0.550) and CSPI after 120 min incubation without enzyme (0.568). These results suggest that PSPI could be used as an ingredient for emulsified products and where high solubility at low pH is required.