Polypeptide profile and functional properties of defatted meals and protein isolates of canola seeds

Laboratory‐defatted meals from four types of canola seeds were analysed for protein profile by reducing and non‐reducing forms of sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS‐PAGE). In the absence of a reducing agent (2‐mercaptoethanol), four major polypeptide bands (16, 18, 30 and 53 kDa) were prominent in similar ratios in all varieties. In the presence of mercaptoethanol, significant reductions in intensity of the major bands occurred, suggesting that the major polypeptides contained smaller units which were held together by disulphide bonds. Meals from Brassica napus seeds had higher protein solubilities than meals from Brassica rapa seeds. Meals with higher protein solubility values also had higher foaming capacity (FC) values. Generally, the acid‐precipitated (pH 4.0) protein isolates (APPIs) had higher FC values than the calcium‐precipitated isolates (CPPIs). On the other hand, the CPPIs formed emulsions with higher values of emulsifying activity index (EAI) when compared to the APPIs. The results indicate that variations in functional properties of protein isolates and meals between the four seed types were probably due to differences in protein conformation in aqueous solutions rather than differences in polypeptide composition. © 2001 Society of Chemical Industry     

榛子分离蛋白提取及其功能特性的研究

以低变性榛子饼为原料,经脱脂后采用碱提酸沉法提取榛子分离蛋白,确定了最佳提取工艺条件,并分析了榛子分离蛋白的功能特性.结果表明,提取榛子分离蛋白的最佳工艺条件为:料液比1:15,碱提pH9.0,碱提温度50℃,碱提时间70 min,酸沉pH4.5.最佳条件下榛子分离蛋白的溶解性、持水性和吸油性分别为34.0%、2.6 mL/g和2.15 mL/g,乳化性、乳化稳定性、起泡性和泡沫稳定性分别为61.2%、85.0%、86.5%和24.0%,榛子分离蛋白的等电点为4.52.     

绿豆中四种蛋白质的分级提取与功能性质研究

采用Osborne方法分级分离了绿豆中的蛋白质,得到四种蛋白组分:清蛋白、球蛋白、醇溶蛋白和谷蛋白,并对其进行功能性质评价。对比评价结果表明:溶解度大小为:清蛋白>球蛋白>谷蛋白>醇溶蛋白;四种蛋白组分中,谷蛋白持水与持油能力较好,清蛋白起泡性较好,醇溶蛋白颜色最好、感官接受度较高,四种蛋白组分在碱性条件下均有较好的乳化性,且均在270~280nm处产生最大吸收峰。      

藜麦蛋白的提取及功能性质与生物活性概述

藜麦被认为是一种营养均衡且全面的假谷物,与传统谷物相比,藜麦蛋白质含量丰富,氨基酸比例均衡,在蛋白质功效比、生物学价值和营养指数等方面都饱具优势。本文主要综述了藜麦蛋白的提取方法和功能性质的研究进展,并对其营养价值和生物活性作了简要概述,目的是为藜麦蛋白的深入研究和相关产品开发提供参考。     

Effect of extraction conditions on composition,surface activity and rheological properties of protein isolates from flaxseed (Linum usitativissimum L)

Flaxseed protein isolates were prepared by micellisation (FM) and isoeletric precipitation (FI). The influence of preparation conditions on composition and functional properties was investigated. Contents of 0.6% phytic acid and 2.3% pentosans were found for FI, whereas FM was almost phytic acid‐free and had a low content of pentosans (0.6%). Chromatography and electrophoresis identified the 11S globulin (linin) as the main protein fraction in both isolates. Protein solubility, water‐ and oil‐binding capacities, emulsification and rheological properties of dispersions and gels were measured at pH 8 and 3. For the latter, interactions of protein with phytic acid and pentosans are highly probable. FI possesses a lower solubility (about 40–50%) and an overall higher water‐binding capacity than FM. For FI dispersions a higher storage modulus G′ than loss modulus G″ was measured, clearly pointing to the formation of protein networks. Moreover, FI formed stronger gels than FM (G′ about fivefold). The emulsifying activity, however, was distinctly lower for FI. These results point to enhanced complexation and aggregation of the isoelectric‐precipitated protein isolate. © 2002 Society of Chemical Industry     

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.     

苜蓿蛋白质的提取及功能性研究

以压块苜蓿为原料提取苜蓿蛋白质,得到的蛋白质含量高达79.72%(干基),研究了蛋白质浓度、温度、pH值和氯化钠浓度对苜蓿蛋白质的吸水性、溶解性、乳化性和起泡性的影响.     

Ultrasound‐induced changes in physical and functional properties of whey proteins

Use of high‐intensity ultrasound to modify certain functional properties of whey proteins is an alternative to traditional method in food industry. Whey protein isolate (WPI) solutions were treated with an ultrasound probe (20 kHz) at different intensities (20% or 30% amplitude) and durations (10 or 20 min). Results showed that ultrasound treatment changed physical and several functional properties of whey proteins including decreased particle size (from 190.4 nm to 138.0 nm), increased surface hydrophobicity (from 5.13 × 10⁵ to 5.77 × 10⁵), free sulphydryl groups (from 52.64 μmol SH g^?1 to 53.64–58.77 μmol SH g^?1), solubility (from 74.95% to 89.70%), emulsion activity index (from 3.18 m² g^?1 to 3.59–5.32 m² g^?1) and emulsion stability index (from 62.26 min to 71.44–104.83 min), and changed viscosity (from 5.51 mPa.s to 4.81–5.64 mPa.s). Therefore, we conclude that high‐intensity ultrasound can be potentially applied to whey proteins to improve its specific functions during food processing.     

Application of ultrasound treatment for modulating the structural,functional and rheological properties of black bean protein isolates

The modulating effect of ultrasound treatments at varying powers and times on the structural and functional properties of black bean protein isolate (BBPI) was investigated. Compared with native BBPI, low-power (150 W) and medium-power (300 W) ultrasound treatments increased the solubility, foaming and emulsifying properties of BBPI, especially at 300 W, 24 min. This effect arises predominantly due to increased exposure of hydrophobic groups, which serve to increase the interactions between the protein and water molecules. Additionally, an increase in the protein surface activity improved the absorption of protein molecules at the oil–water and air–water interfaces. Rheology data showed that increased hydrophobic and hydrogen-bonding interactions improved the water-holding capacity of BBPI gels following ultrasound treatment. However, high-power (450 W) ultrasound treatment weakened the functional properties of BBPI, and this was likely due to the formation of macromolecular BBPI aggregates. Overall, this study indicates that ultrasound treatment could be a promising approach for modulating other plant protein resources as well as expanding the application of black bean protein.     

赤藓糖醇对豌豆分离蛋白结构和功能特性的影响

为研究赤藓糖醇对豌豆分离蛋白结构和功能特性的影响,利用8-苯胺基-1-萘磺酸钠荧光探针法、紫外和荧光光谱法,研究赤藓糖醇对豌豆分离蛋白溶解性、持水性、起泡性、乳化性及表面疏水性等的影响。结果表明:随赤藓糖醇质量分数的增加,豌豆分离蛋白的溶解性基本呈先增加后下降趋势,且均在pH4.0处最低。持水性逐渐增加,且均在pH5.0处最低。起泡性和乳化性均先增加后趋于平稳。当赤藓糖醇质量分数在0~10%范围内,表面疏水性逐渐增加,随后趋于稳定。随赤藓糖醇质量分数增加,色氨酸残基暴露在蛋白质分子表面,荧光强度先增加后趋于稳定,且与表面疏水性变化趋势相同。该研究表明,适度赤藓糖醇处理可改善豌豆分离蛋白的结构和功能特性。     

超声辅助提取黑豆蛋白及其功能性质的研究

以黑豆为原料,利用响应面分析方法对超声辅助提取黑豆蛋白的工艺参数进行了优化,得到最优参数:超声时间为24min,p H9.7,超声功率为380W,液固比为11∶1。在此工艺参数条件下黑豆蛋白提取率可达56.26%。同时对比传统碱溶酸沉提取得到的黑豆蛋白与超声辅助提取出的黑豆蛋白的溶解性,乳化性与乳化稳定性,起泡性和起泡稳定性,研究发现超声辅助提取的黑豆蛋白的各种功能性质都有所提高。      

沙棘籽粕蛋白的碱酶两步法提取工艺及功能性研究

以沙棘籽粕为原料,采用碱提酸沉法提取沙棘籽粕蛋白,得到最佳提取工艺参数为:pH10、料液比1:12、温度60℃、时间60min。后用碱性蛋白酶对碱提残渣中的蛋白进行水解,最适提取条件为:pH8.5、碱性蛋白酶加酶量240U/g、料液比1:10、60℃、60min。通过碱提、酶法两步提取后,总提取率为67.24%。并对其乳化活力和乳化稳定性等功能性质进行了研究,表明性质受pH、温度、盐离子浓度等环境因素影响大,在等电点pH5.0附近时乳化活力和乳化稳定性的数据最低。      

Rheological and Microstructural Characteristics of Canola Protein Isolate−Chitosan Complex Coacervates

Wastage of byproducts such as canola meal is a pressing environmental concern, and canola protein isolate (CPI)?chitosan (Ch) coacervates have a good potential to utilize and convert the wastes into a high value added product. Yet so far, there is very limited rheological and microstructural information to assist in proper utilization of CPI ‐Ch complex coacervates. The rheological and microstructural properties of the complex coacervates formed from CPI and chitosan Ch at various CPI‐to‐Ch mixing ratios (1:1, 16:1, 20:1, and 30:1) and pH values (5.0, 6.0, and 7.0) were therefore investigated. These CPI?Ch complex coacervate phases were found to exhibit elastic behavior as evidenced by significantly higher elastic modulus (G?) compared to viscous modulus (G″) in all the tested ratios and pH ranges. They also exhibited shear‐thinning behavior during viscous flow. The complex coacervates formed at the optimum CPI‐to‐Ch ratio of 16:1 and pH of 6.0 demonstrated the highest G?, G″, and shear viscosity, which correlated well with the high strength of electrostatic interaction and thick‐walled, sponge‐like, less‐porous microstructure at this condition. The higher shear viscosity of the coacervate at pH 6.0 was most likely induced by stronger attractive electrostatic interactions between CPI and Ch molecules, due to the formation of a rather densely packed complex coacervate structure. Hence, it can be concluded that the microstructural observations of denser structure correlated well with the rheological findings of stronger intermolecular bonds at the optimum CPI‐to‐Ch ratio of 16:1 and pH of 6.0. The complex coacervate phase formed at a CPI‐to‐Ch ratio of 16:1 and pH of 6.0 also showed glassy consistency at low temperatures and rubbery consistency above its glass‐transition temperature. This study identified the potential for the newly developed CPI–Ch complex coacervate to be used as an encapsulating material due to its favorable strength. This would drastically reduce the wastage of byproducts, provide a solution to tackle the pressing global issue of wastage of byproducts, and bring about a more environmentally friendly paradigm.     

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.     

热烘改性对大豆分离蛋白功能性的影响

研究了利用热处理对大豆分离蛋白(SPI)进行改性。热烘改性对SPI的吸水性、吸油性、发泡性和泡沫稳定性无显著性影响,常温粘度、高温粘度、耐热性、凝胶性和保水性分别比对照提高了118%、135%、108%、81%和83%。比较适宜的热烘改性条件为10min/85℃。     

Effects of protein separation conditions on the functional and thermal properties of canola protein isolates

Canola meal protein isolates were prepared from defatted canola meal flour using alkaline solubilization and acid precipitation. A central composite design was used to model 2nd-order response surfaces for the protein yield and the functional properties of protein isolates. The solubilization pH and precipitation pH were used as design factors. The models showed that the protein yield and functional properties of isolates, such as water absorption and fat absorption, were sensitive to both solubilization pH and precipitation pH, whereas the emulsification was sensitive to only solubilization pH. Gel electrophoresis analysis of protein fractions gave evidence to the compositional changes between proteins isolated under different conditions. Differences in glass transition temperatures suggest that proteins tend to be more denatured when solubilized at highly alkaline conditions. These conformational and compositional changes due to different protein separation conditions have contributed to the changes in functional properties of protein isolates. PRACTICAL APPLICATION: Protein isolation conditions may be determined primarily through optimization of total protein yield. Improvements in protein functional properties may be achieved with a relatively small sacrifice in yield by altering isolation conditions.     

乙酰化大豆分离蛋白的功能特性研究

本文采用乙酸酐对大豆分离蛋白进行改性。测定了改性前后,不同改性程度下大豆分离蛋白功能特性的变化。结果表明：乙酰化大豆蛋白在5.0-9.5范围内大大提高发泡性能、乳化性能,并使等电点朝酸性偏移。