Preparation and Characterization of Protein Isolate from Cowpea (Vigna unguiculata L. Walp.)

ABSTRACT: Protein isolate (PI) was prepared from 3 cowpea varieties and 2 soybean varieties in each of 2 y. The protein contents of cowpea PI (CPI) (91.4% to 91.8%) and soy PI (SPI) (93.0% to 93.5%) were significantly different ( P < 0.05). Electrophoretogram showed that CPI was concentrated at 60 and 40 kDa, whereas SPI showed bands at 95, 65, 60, 40, and 35 kDa. The CPI had higher lysine (49.3 to 51.8 mg/g) than SPI (41.9 to 43.4 mg/g). The CPI and SPI had surface hydrophobicities ranging from 387.8 to 572.9 and 640.6 to 643.1, respectively. Denaturation temperature (85.2 to 88.4 °C) and enthalpy (8.42 to 10.33 J/g) of CPI were similar to the 7S fraction of SPI (82.6 °C and 96.0 to 96.3 J/g). These characteristics of CPI might be useful to explain its functionalities for application in food systems.     

减压等离子体处理对大豆分离蛋白功能性质的影响

运用减压等离子体处理大豆分离蛋白(soybean protein isolate,SPI),研究处理时间对SPI溶解性、乳化活性、触变性、热稳定性及表面粗糙度等功能性质的影响。结果表明:经100 W的减压等离子体处理150 s后,SPI的溶解度、乳化活性指数和吸水性均达到最大,分别为572.83μg/mL、0.584 m2/g和12.675 g/g,比对照分别增加约35%、15%和48%;吸油性随着处理时间的延长呈现先降低后上升的趋势,当处理时间为300 s时达到最大值2.071 mL/g,比对照增加了12%;流变学研究表明减压等离子体处理使SPI的黏度有所降低,但未影响其触变性及剪切变稀行为;差示扫描量热分析表明减压等离子体处理略微降低了SPI的热稳定性,扫描电子显微镜观察结果则表明减压等离子体处理增加了SPI颗粒的表面粗糙度。上述研究表明,减压等离子体处理可以改善SPI的溶解性、乳化性、吸水性、吸油性,因此在SPI的改性中具有潜在的应用价值。     

湿法糖基化改性对大豆分离蛋白功能性质的影响

大豆分离蛋白与葡萄糖按质量比4∶1溶解在重蒸水中配制成蛋白质质量浓度为8 g/100 mL的混合液,分别在70、80、90 ℃条件下反应0、1、2、3、4、5、6 h,得到不同反应温度和时间的糖基化产物。通过测定各糖基化产物的pH值、溶解性、乳化性和凝胶性质,研究糖基化对大豆分离蛋白功能性质的影响。结果表明：随着加热时间的延长,不同温度反应体系的颜色加深,pH值逐渐降低,溶解性、乳化活性和乳化稳定性显著提高,凝胶的弹性和硬度呈先上升后下降的趋势。其中90 ℃反应体系糖基化大豆分离蛋白的功能性质提高最为明显,从0 h到6 h,溶解性和乳化活性分别从17.37%、0.168提高到了38.7%、0.574,且效果显著（P＜0.05）;加热4 h制得的糖基化样品的乳化稳定性最强,其乳化稳定性为39.6;并且糖基化样品凝胶的硬度和弹性在反应3 h时最大,其硬度和弹性分别为81.3g和0.936。因此,糖基化修饰可有效提高大豆分离蛋白的功能性质。     

大豆分离蛋白溶解性和乳化性影响因素研究

研究了pH、大豆分离蛋白(SPI)质量浓度、NaCl浓度、搅拌时间和温度等因素对SPI溶解性和乳化性的影响.结果表明,0.8%的SPI在pH 6.0的条件下,实验浓度范围内的NaCI均使SPI溶解性和乳化性降低,适当的延长搅拌时间和升高温度可以显著提高SPI溶解性和乳化性.在室温条件下,搅拌50 min时SPI溶解度最...     

Solubility,functional properties,ACE‐I inhibitory and DPPH scavenging activities of Alcalase hydrolysed soy protein hydrolysates

Soy proteins are less soluble at acidic pH value, which impedes their utilisation in acidic beverages. Soy protein isolate (SPI) was hydrolysed using varying Alcalase concentrations (0.0001–2.0 U g^?1 protein) at different pHs (3.0–4.0). Degree of hydrolysis (DH) of soy protein hydrolysates (SPH) at pH 3.0, 3.5 and 4.0 were 5.0–10.7%, 2.3–6.1% and 0–5.4%, respectively, while solubilities ranged from 70.7 to 74.9%, 18.8 to 51.2% and 7.1 to 40.4%, respectively. The highest solubility (74.9%) was observed at pH 3.0 with 1.5 U Alcalase per g protein (DH = 9.2%). Emulsifying activities of SPHs at pH 3.0 and 4.0 ranged from 0.49 to 0.63 AU and 0.19 to 0.24 AU, respectively, while the emulsifying stabilities were 12.2–14.7 min and 18.7–56.0 min, respectively. The foaming capacity at pH 3.0 and 4.0 was 44.9–46.3 mL and 31.2–41.3 mL, respectively, whereas the foaming stability was 25.5–35.2 min and 12.8–15.1 min, respectively. However, hydrolysates had an insignificant effect on ACE‐I inhibitory and DPPH scavenging activities in comparison with SPI.     

预热处理大豆蛋白对鲤鱼肌原纤维蛋白凝胶和流变学特性的影响

以鲤鱼肌原纤维蛋白（myofibrillar protein isolate,MPI）为研究对象,研究经过预热处理的大豆分离蛋白（soy protein isolate,SPI）对MPI凝胶和流变学特性的影响。SPI在90 ℃热处理0（天然SPI）、30 min和180 min,分别与MPI以不同的比例（0∶1、1∶1、1∶2、1∶3、1∶4）混合,所有溶液总蛋白质量浓度均为40 mg/mL。结果表明,经过预热处理的SPI与MPI混合后其凝胶硬度、弹性、白度和持水性显著高于天然SPI与MPI混合所形成的蛋白凝胶（P＜0.05）,且预热处理时间越长的大豆蛋白（180 min）与短时间处理（30 min）相比增加得更为明显（P＜0.05）。此外,随着SPI-MPI复配1∶1～1∶4,混合蛋白凝胶硬度、弹性、白度和持水性显著增大（P＜0.05）。流变学研究表明,SPI添加到MPI溶液中能增加蛋白变性温度,而经过预热处理SPI能够显著地提高储能模量（G’）。热稳定性结果表明,MPI中添加天然SPI能够显著降低Tmax3（P＜0.05）而对Tmax1和Tmax2无影响（P＞0.05）;当SPI经过热处理后添加到MPI中能够显著降低Tmax1（P＜0.05）而提高Tmax3（P＜0.05）。总之,与未经预热处理的SPI相比,经过预热处理后的SPI添加到MPI中能够改善蛋白凝胶特性和流变学特性。     

紫苏分离蛋白功能性研究

为了开发紫苏蛋白在食品工业中的应用,以大豆分离蛋白为对照,研究紫苏分离蛋白的功能特性。结果表明：紫苏分离蛋白的溶解性与大豆分离蛋白的溶解性随pH值变化的趋势基本一致,但在等电点时紫苏分离蛋白的溶解性高于大豆分离蛋白。在pH7.0时,紫苏分离蛋白的持水性、起泡性及泡沫稳定性、乳化性和凝胶性均不及大豆分离蛋白。但紫苏分离蛋白的吸油性仅稍小于大豆分离蛋白,此外,在紫苏分离蛋白的蛋白质质量浓度为3g/100mL以后,其乳化稳定性与大豆分离蛋白的乳化稳定性基本相当。紫苏分离蛋白在食品加工中作为一种蛋白质强化剂具有一定潜力。     

Use of plant protein isolates in processed cheese

Plant protein isolates were evaluated and used to replace skim milk powdered protein in processed cheese blends. The chemical composition of chickpea protein isolate (CPI), peanut protein isolate (PPI) and sesame protein isolates (SPI) were determined. Functional properties of the tested protein isolates were also studied. SPI had minimum emulsion activity index (EAI), while the PPI possessed the highest value. The emulsions formed remained stable after one day, then destroyed at the 3rd day. Water absorption capacity (WAC) of the tested protein isolates varried between 196 to 329 g water/100 g protein. The water-oil absorption index (WOAI) for CPI, PPI and SPI were 7.6, 0.48 and 0.90, respectively. Changes in chemical composition of plant-type processed cheeses containing different levels of plant protein isolates (5, 10 and 15%), occurred only in total nitrogen, while the other constituents such as total solids, fat and salt were not affected. Sensory evaluation of the processed cheese revealed that total score gradually decreased with increasing plant-protein isolate levels up to 15% but still preferable for the consumer. This decrease in the total score regards the flavour but not to the colour or body and texture.     

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.     

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。     

Physico-Chemical Properties of the Flour, Protein Concentrate, and Protein Isolate of the Cupuassu (Theobroma grandiflorum Schum) Seed

ABSTRACT:  Defatted flour, protein concentrate, and protein isolate obtained from Amazonian cupuassu seeds were evaluated for their solubility properties, water and oil retention capacity, foam formation and stability, gelling properties, emulsifying ability, and emulsion stability. The protein contents of defatted flour, the concentrate, and the isolate were 27.65%, 31.18%, and 64.29%, respectively. As expected, the protein isolate exhibited higher solubility than the protein concentrate, achieving more than 90% solubility at pH 8.0. The flour and the protein concentrate, however, showed excellent water and oil retention capacities. High emulsifying capacity at pH 7.0 was also observed for all 3 products: 987 mL oil/g, 977 mL oil/g, and 1380 mL oil/g for the flour, protein concentrate, and protein isolate, respectively. Gelling properties were not exhibited by any of the products, but all of them exhibited good utilization potential, not only to enrich other foods but also to enhance relevant functional properties.     

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...     

Antioxidant activities and functional properties of soy protein isolate hydrolysates obtained using microbial proteases

Soy protein isolate (SPI) hydrolysates were prepared using microbial proteases to produce peptides with antioxidant activity. The process parameters (substrate and enzyme concentrations), hydrolysis time, functional properties and the effects of ultrafiltration were further investigated. The results showed that the soy protein isolate exhibited a 7.0‐fold increase in antioxidant activity after hydrolysis. The hydrolysis parameters, defined by the experimental design, were a substrate concentration of 90 mg mL^?1 and the addition of 70.0 U of protease per mL of reaction. The maximum antioxidant activities were observed between 120 and 180 min of hydrolysis, where the degree of hydrolysis was approximately 20.0%. The hydrolysis increased solubility of the soy protein isolate; however, the hydrolysates exhibited a tendency to decrease in the interfacial activities and the heat stability. The SPI hydrolysates fractions obtained by ultrafiltration showed that the enzymatic hydrolysis resulted in samples with homogenous size and strong antioxidant activity.     

Improvement of functional properties of chickpea proteins by hydrolysis with immobilised Alcalase

Limited chickpea protein hydrolysates ranging from 1% to 10% degree of hydrolysis were produced from chickpea protein isolate (CPI) using Alcalase immobilised on glyoxyl-agarose gels. Alcalase-glyoxyl derivative produced after 24 h of immobilisation at room temperature was 24 times more stable than soluble enzyme and presented approximately 51% of the activity of Alcalase. The chemical composition of chickpea hydrolysates were very close to that of CPI. Solubility, oil absorption, emulsifying activity and stability, and foaming capacity and stability were determined. All protein hydrolysates showed higher solubility than intact proteins, especially at pHs near isoelectric point of native chickpea proteins. Moreover, all hydrolysates had better functional properties, except emulsifying activity, than the original protein isolate.     

Influence of pH Shift on Functional Properties of Protein Isolated of Tilapia (<Emphasis Type="Italic">Oreochromis niloticus</Emphasis>) Muscles and of Soy Protein Isolate

The physicofunctional and chemical properties of acid-aided protein isolate (AcPi), alkaline-aided protein isolate (AlPi) and soy protein isolate (SPI) prepared from tilapia muscle and defatted soy flour as a function of pH and/or NaCl concentration were investigated. Both acid- and alkali-aided processes lead to significant recoveries (P < 0.05) of proteins with substantial reduction of lipids in AlPi (0.81%) and AcPi (0.96%), the lowest for SPI (0.336%) facilitated by the processing method and sample used. There is greater lipid reduction at alkali pH, effective removal of impurities such as bones and scales, indicated by percentage ash (AcPi, 4.53%; AlPi, 3.75% and SPI, 3.51%). No major difference noted in sodium dodecyl sulphate polyacrylamide gel electrophoresis protein bands (14.4–97.4 kDa) possibly representing partial hydrolysis of myosin. Solubility was the highest at pH 3.0 and 11.0 and the lowest at isoelectric point with foam capacity showing similarity at varying pH. The addition of NaCl improved foam stability, possibly due to the increased solubility and surface activity of the soluble protein. On the whole, AcPi, AlPi and SPI manifested lower solubility and foamability at pH 4.0 and 5.0. AlPi exhibited appreciable levels of solubility, emulsion capacity, oil-holding capacity, viscosity and whiteness, whereas SPI had appreciable water-holding capacity. AcPi, AlPi and SPI have excellent relevance for product development based on their functionality.     

Assessment of functionality of sesame meal and sesame protein isolate from Indian cultivar

Plant proteins are cheaper source of proteins as compared to animal proteins. So they have great potential as functional food ingredient and could be supplemented in human diets. The use of isolated proteins depends on their ability to impart properties in processed foods. So for effective utilization of particular protein, it is necessary to study its all types of properties and characteristics which is necessary for development of methodology for their use. Sesame protein isolate (SPI) was extracted from sesame meal. The physicochemical and functional properties of both sesame meal and SPI were evaluated. The solubility was maximum (94.13 %) at pH 12. Foaming capacity and foam stability of SPI was pH dependent. SPI showed increase in emulsion stability (ES) with increase in pH. Gelling ability of SPI increased with alkaline pH.     

巯基乙醇对大豆分离蛋白热致聚合物界面性质的影响

为探讨β-巯基乙醇对大豆分离蛋白热致聚合物界面性质的影响,以大豆分离蛋白为原料,在pH7.0、90 ℃加热添加和不添加β-巯基乙醇（2 mmol/L）浓度为10 mg/mL的大豆分离蛋白溶液0 h和10 h,制备不同大豆分离蛋白质热致聚合物。观察了大豆分离蛋白、添加β-巯基乙醇大豆分离蛋白、大豆分离蛋白热致聚合物和β-巯基乙醇大豆分离蛋白热致聚合物的微观形态、游离巯基含量的变化,同时比较了起泡能力、泡沫稳定性、乳化活性、乳化稳定性、表面疏水性和浊度的差异。结果表明,大豆分离蛋白和添加β-巯基乙醇大豆分离蛋白呈现无规则状态,大豆分离蛋白热致聚合物为有规则的球状颗粒,而β-巯基乙醇大豆分离蛋白热致聚合物部分形成球状聚合物部分形成无规则聚合物。添加β-巯基乙醇改善了大豆分离蛋白的界面性质。与大豆分离蛋白相比较,添加β-巯基乙醇大豆分离蛋白和添加β-巯基乙醇大豆分离蛋白热致聚合物的起泡能力分别提高了64.56%和95.77%,乳化活性提高的幅度分别为12.94%和14.61%。添加β-巯基乙醇大豆分离蛋白和添加β-巯基乙醇大豆分离蛋白热致聚合物在长时间储藏中表现出良好的乳化稳定性和泡沫稳定性。这种良好的界面性质源于β-巯基乙醇的加入赋予聚合物具有更高的游离巯基含量和表面疏水性。并且本实验建立了4种样品的泡沫稳定性和乳化稳定性随时间变化的Rational函数和Linear函数经验模型,为大豆分离蛋白质的实际应用奠定了理论基础。     

茶叶籽粕蛋白功能特性研究

以大豆分离蛋白为对照,研究碱法和酶法提取茶叶籽粕蛋白的功能特性。结果表明：酶法提取茶叶籽粕蛋白的溶解性、吸油性、乳化能力和乳化稳定性、起泡性、凝胶脆度优于碱法提取茶叶籽粕蛋白,而后者的吸水性、泡沫稳定性则优于前者,两者所形成蛋白凝胶的黏性和硬度相当。碱法和酶法提取的茶叶籽粕蛋白的乳化能力和乳化稳定性稍优于大豆分离蛋白,但起泡性和泡沫稳定性则不及大豆分离蛋白,溶解性与大豆分离蛋白相当,它们形成凝胶的最低质量分数分别为13%和15%,凝胶的黏性和硬度低于大豆分离蛋白。pH值、蛋白质量分数、NaCl浓度等因素对茶叶籽粕蛋白功能特性均有不同程度的影响。     

Xanthan Gum Effects on Solubility and Emulsification Properties of Soy Protein Isolate

The effect of xanthan gum (XG) on solubility and emulsifying properties of soy protein isolate (SPI) was evaluated. The solubility of SPI was increased by addition of XG (p < 0.05). The emulsifying activity of SPI-XG was 4 times higher than that of SPI or XG alone (p < 0.05) and similar to that of bovine serum albumin (BSA) (P > 0.05). The emulsifying stability of SPI-XG dispersions was respectively 3 and 2 times higher than that of SPI and BSA (p < 0.05). The solubility and emulsifying properties of SPI-XG dispersions were stable over a wide range of pH (3.0 to 9.0), ionic strength (0.1 to 1.0M NaCl), and heat (85°C, 1 hr).     

Relationship of hydrophobicity and solubility with some functional properties of cowpea (Vigna unguiculata) protein isolate

The relationship of hydrophobicity and solubility with some functional properties of cowpea protein isolate was determined. Cowpea protein isolate was prepared by alkali extraction followed by precipitation at pH 4.5. The precipitated proteins were then neutralized to pH 7. Heating of the protein isolate to 100°C for 10 min followed by cooling to room temperature resulted in a significant (P ≦ 0.05) decrease in aromatic hydrophobicity (ARH) when compared to the native protein isolate. The inclusion of sodium dodecyl sulfate (SDS) during heating gave a significant (P ≦ 0-05) 1.7-fold increase while inclusion of mercaptoethanol (ME) gave a significant (P ≦ 0.05) 2.5-fold increase in ARH of the cooled protein solution. Protein solubility (PS), foam expansion (FE) and emulsification activity index (EAI) of the isolate generally increased significantly (P ≦ 0.05) upon heating or treatment with urea or SDS or a combination of SDS and ME. Backward stepwise multiple regression was used to obtain equations for predicting emulsifying and foaming properties of the protein isolate from solubility and hydrophobicity parameters. PS, ARH and aliphatic hydrophobicity (ALH) were important in predicting foam stability and emulsion stability, while PS and ALH were important for predicting FE. ALH alone was important for predicting EAI.