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1.
Some nutritional and functional properties of defatted wheat germ protein   总被引：24，自引：0，他引：24  
Defatted wheat germ protein (DWGP) was isolated by alkaline extraction at pH 9.5 and subsequent isoelectric precipitation at pH 4.0, and its nutritional and functional properties were studied. The results showed that the amino acid content of defatted wheat germ was as high as 26.793 g/100 g, and the contents of eight essential amino acids were all relatively high. The isoelectric point of DWGP was 4.0. When pH >6.0, the DWGP had high solubility with a nitrogen solubility index of 70%. The emulsifying activity and emulsifying stability of DWGP were similar to those of bovine serum albumin and a little higher than those of casein. DWGP had good foaming capacity, but its foaming stability (FS) was not very good. However, the FS of DWGP can be improved through physical, chemical, or enzymatic methods. Moreover, DWGP had excellent water retention (WR); especially at pH 8.0 and a temperature of 70 degrees C, the WR of DWGP was the highest at 229.4%. DWGP offers is a potential source of functional protein isolate for possible food applications.  相似文献   

2.
Preparation and functional properties of rice bran protein isolate   总被引：39，自引：0，他引：39  
Rice bran protein isolate (RBPI) containing approximately 92.0% protein was prepared from unstabilized and defatted rice bran using phytase and xylanase. The yield of RBPI increased from 34% to 74.6% through the use of the enzymatic treatment. Nitrogen solubilities of RBPI were 53, 8, 62, 78, 82, and 80% at pHs 2.0, 4.0, 6.0, 8.0, 10.0, and 12.0, respectively. Differential scanning calorimetry showed that RBPI had denaturation temperature of 83.4 degrees C with low endotherm (0.96 J/g of protein). RBPI had similar foaming properties in comparison to egg white. But emulsifying properties of RBPI were significantly lower than those of bovine serum albumin. The result of amino acid analysis showed that RBPI had a similar profile of essential amino acid requirements for 2-5-year-old children in comparison to that of casein and soy protein isolate.  相似文献   

3.
Protein isolates extracted from differently stabilized rice bran were analyzed to work out the food use potential. Bulk density remained higher for isolates obtained from heat stabilized bran, the treatments were found to have positive impact on the oil absorption properties, while the water absorption was slightly impaired owing to some possible configurational changes. Surface hydrophobicity and emulsion properties were improved with bran stabilization. Isolates exhibited better foaming properties owing to the flexible nature of protein molecules, with less intensive disulfide bonding, that were slightly affected by the stabilization treatment. Nitrogen solubility index followed a curved pattern with the least value near isoelectric point that showed an increasing trend toward basic pH, and parboiled protein isolates exhibited better gelling properties among the isolates.  相似文献   

4.
燕麦麸分离蛋白的酶解对其功能性质的影响   总被引：4，自引：3，他引：4  
为了改善燕麦蛋白的功能性质以扩大其在食品工业中的应用，该文以燕麦麸为原料制备了燕麦麸分离蛋白(OBPI)，并利用胰蛋白酶对其进行水解，得到了3种不同水解度(4.1%、6.4%、8.3%)的酶解产物。SDS-PAGE分析结果表明OBPI中的主要蛋白成分是球蛋白，其经过胰蛋白酶处理后，球蛋白酸性亚基被部分水解而碱性亚基相对保持完整。胰蛋白酶水解显著改变了OBPI的功能性质。在所考察的水解度范围内，随着水解度的升高，酶解产物的溶解性、持水性、乳化活性及起泡能力等方面均逐渐增加；但持油性、乳化及泡沫稳定性有不同程度的降低。  相似文献   

5.
Rice proteins are nutritional, hypoallergenic, and healthy for human consumption. Efficient extraction with approved food‐grade enzymes and chemicals are essential for commercial production and application of rice protein as a functional ingredient. Rice endosperm proteins were isolated by alkali, salt, and enzymatic methods and evaluated for extractability and physicochemical properties. Alkali (RPA) and salt (RPS) methods extracted 86.9 and 87.3% of proteins with 65.9 and 58.9% yield, respectively. The enzymatic methods with Termamyl (RPET) and amylase S (RPEA) extracted 85.8 and 81.0% proteins with 85.2 and 86.2% yield, respectively. Enthalpy values of RPA (1.79 J/g), RPS (1.22 J/g), RPET (nondetectable), and RPEA (0.17 J/g), determined by differential scanning calorimetry, demonstrated that the varying level of denaturation of proteins depends on the method of extraction. Surface hydrophobicity data supported this observation. Alkali‐ and salt‐extracted proteins had higher solubility and emulsifying properties than those of enzyme‐extracted proteins. Comparatively, more favorable protein composition, lower surface hydrophobicity, higher solubility, and a lower degree of thermal denaturation of alkali‐ and salt‐extracted proteins contributed to higher emulsifying and foaming properties than those of enzyme‐extracted proteins; therefore, alkali‐ and salt‐extracted proteins can have enhanced functional use and a potential starting material for preparing tailored rice protein isolates.  相似文献   

6.
该文研究了不同制备方法对花生浓缩蛋白功能性的影响,以期为不同制备方法制得的花生浓缩蛋白在食品中的广泛应用提供理论支持。以脱脂花生蛋白粉（DPF）为原料,通过等电沉淀、乙醇浸提、等电沉淀与乙醇浸提相结合及碱溶酸沉技术制备花生浓缩蛋白,并分别测定其蛋白功能性（蛋白溶解性、吸水性、持油性、乳化能力及乳化稳定性、起泡能力及泡沫稳定性、凝胶性质）。结果表明：碱溶酸沉技术制备的蛋白溶解性、起泡能力及泡沫稳定性最好;而乙醇浸提制备的蛋白吸水性、持油性和凝胶性质要显著性的高于其他方法制备的蛋白产品的;不同方法制备的花生浓缩蛋白的乳化稳定性均明显低于对照（DPF）,尤以碱溶酸沉技术制备的最低。因此可知,乙醇浸提制备的蛋白适用于对吸水性、持油性和凝胶性质要求较高的食品中;碱溶酸沉技术制备的蛋白适用于对起泡能力要求较高的食品中。  相似文献   

7.
The major storage globulins (vicilins) of cowpea (Vigna unguiculata) and pea (Pisum sativum) seeds were purified by ammonium sulfate precipitation, and a semipurified cowpea protein isolate (CPI) was prepared by isoelectric precipitation. Some of the functional properties of these proteins, including solubility, foaming, and emulsifying capacities, were investigated and compared. The solubility of purified cowpea vicilin was reduced at pH 5.0, increasing markedly below and above this value. Pea vicilin exhibited poor solubility between pH 5.0 and pH 6.0, and CPI was little soluble in the pH range from 4.0 to 6.0. At neutral pH, the emulsifying activity indexes (EAI) of purified pea vicilin and CPI were 194 and 291 m(2)/g, respectively, which compare quite favorably to EAIs of 110 and 133 m(2)/g for casein and albumin, respectively. Remarkably, purified cowpea vicilin exhibited an EAI of 490 m(2)/g, indicating a very high emulsifying activity. Purified cowpea and pea vicilins exhibited lower foaming capacities and foam stablity indexes (FSI) than CPI. FSI values of 80 and 260 min were obtained for purified pea and cowpea vicilin, respectively, whereas a FSI value of 380 min was obtained for CPI. These results are discussed in terms of the possible utilization of purified vicilins or protein isolates from pea and cowpea in the food processing industry.  相似文献   

8.
为提升大豆分离蛋白（soy protein isolate,SPI）的功能性质,该文引入大豆可溶性多糖（soybean soluble polysaccharides,SSPS）,构建大豆分离蛋白-大豆可溶性多糖体系（SPI-SSPS）,研究动态高压微射流（dynamic high-pressure microfluidization,DHPM）处理对SPI-SSPS功能特性的影响。分别采用0,60,100,140和180 MPa的 DHPM压力处理SPI-SSPS,探究不同压力对SPI-SSPS起泡特性、乳化特性、溶解性、粒度分布和表面疏水性的影响。结果表明,DHPM处理能提高SPI的溶解性和起泡特性,且SSPS的存在能显著提高DHPM对SPI功能性质的改善效果（P<0.05）。100和60 MPa的DHPM处理能使SPI-SSPS呈现较高的起泡能力和起泡稳定性,分别为未处理样品的1.2和2.4倍。140 MPa的DHPM处理使SPI-SSPS溶解性较强,为未处理样品的1.8倍。然而,DHPM处理会显著降低SPI-SSPS的乳化特性、粒径和表面疏水性（P<0.05）。随着处理压力的增加,SPI-SSPS的粒度和表面疏水性逐渐降低,在180MPa的DHPM处理下SPI-SSPS具有较小的粒径和较低的荧光强度。综上所述,DHPM结合SSPS改性技术可用于改善SPI的功能性质（如溶解性、起泡性）,促进SPI在食品工业的应用。该文的研究结果可为SPI的功能性质改性提供参考。  相似文献   

9.
Rice endosperm protein was modified to enhance solubility and emulsifying properties by controlled enzymatic hydrolysis. The optimum degree of hydrolysis (DH) was determined for acid, neutral, and alkaline type proteases. Solubility and emulsifying properties of the hydrolysates were compared and correlated with DH and surface hydrophobicity. DH was positively associated with solubility of resulting protein hydrolysate regardless of the hydrolyzing enzyme, but enzyme specificity and DH interactively determined the emulsifying properties of the protein hydrolysate. The optimum DH was 6–10% for good emulsifying properties of rice protein, depending on enzyme specificity. High hydrophobic and sulfhydryl disulfide (SH-SS) interactions contributed to protein insolubility even at high DH. The exposure of buried hydrophobic regions of protein that accompanied high-temperature enzyme inactivation promoted aggregation and cross-linking of partially hydrolyzed proteins, thus decreasing the solubility and emulsifying properties of the resulting hydrolysate. Due to the highly insoluble nature of rice protein, surface hydrophobicity was not a reliable indicator for predicting protein solubility and emulsifying properties. Solubility and molecular flexibility are the essential factors in achieving good emulsifying properties of rice endosperm protein isolates.  相似文献   

10.
为提高米糠谷蛋白功能性质,本研究对米糠谷蛋白与β-环状糊精进行复合热处理（温度60、70、80、90、99℃,时间40、80、120、160、200 min）,分析复合聚集体的浊度、接枝度、乳化性质及结构特性等,探究米糠谷蛋白与β-环状糊精复合热聚集行为。结果表明,米糠谷蛋白与β-环状糊精在90℃条件下加热复合160 min时,复合聚集体乳化活性指数达到最大,与天然米糠谷蛋白相比提高了2.39倍;在80℃条件下加热复合200 min时,复合聚集体乳化稳定性指数最大,与天然米糠谷蛋白相比提高了2.39倍。复合物在80℃条件下受热后,米糠谷蛋白与β-环状糊精结合生成较大颗粒的聚集体;复合物中米糠谷蛋白肽链结构打开,游离巯基含量增加,二硫键断开,疏水基团暴露,β-折叠向α-螺旋和β-转角转化,以共价键的形式形成分子间氢键,使得复合聚集体分子更好地结合到油水的界面,复合聚集体乳化活性和稳定性显著提高（P<0.05）。本研究结果为后续米糠蛋白质功能性质的改善及米糠蛋白质的深加工提供了理论依据。  相似文献   

11.
The objectives of this work were to investigate the nutritional and physicochemical characteristics as well as the functional properties of quinoa protein isolates (QPI) from different varieties, and to determine their potential use of such protein isolates in food products. Proteins were isolated by isoelectric precipitation at pH 5 from quinoa flour, and the QPI had a protein percentage of over 85%. The comparison of the flours and QPI electrophoretic profiles indicated that the extraction method allowed isolating practically all proteins of each variety. All the varieties analyzed had high lysine content, compared with cereals, and the essential amino acid content of Bolivian varieties was higher than varieties from Peru. The pH value affected the solubility and foaming capacity, and the magnitude of effects depended on the variety. Cluster analysis showed a strong influence of variety source and amino acid composition on protein physicochemical and functional properties; samples from Bolivia (cluster 2) were characterized as having the highest thermal stability, oil binding capacity, and water binding capacity at acid pH; samples from Peru (cluster 1) had the highest water binding capacity at basic pH and foaming capacity at pH 5. QPI presented a potential as an alternative vegetable protein for food application, in particular for vegetarian and vegan diets.  相似文献   

12.
To utilize lupin seeds for food and pharmaceutical applications, lupin seeds were pretreated to remove oil using hexane or carbon dioxide. Two types of lupin protein isolate were prepared. Both types of protein isolate showed good foaming activity, comparable to egg white. Protein isolate extracted under acid conditions showed higher foaming activity than protein isolate extracted at neutral pH. The lipoxygenase activity was much reduced in both of the protein isolates. The protein isolate extracted at neutral pH showed a stronger angiotensin converting enzyme inhibition than the protein isolate extracted under acidic pH. In contrast, the protein isolate extracted under acid conditions had a greater sodium cholate binding capacity, comparable to that of cholestyramine. Lupin samples showed less DPPH radical scavenging activity than deoiled soybean. The deoiling method did not affect the functional properties, lipoxygenase activity, angiotensin converting enzyme inhibition, sodium cholate binding, and radical scavenging activity.  相似文献   

13.
The non-covalent interactions between the monomeric phenolic compound chlorogenic acid (5-CQA) and bovine serum albumin (BSA), lysozyme, and alpha-lactalbumin were characterized, and their effect on protein properties was examined. 5-CQA had a low affinity for all three proteins, and these interactions seemed to show a negative cooperativity. 5-CQA-BSA binding decreased with increasing temperature, whereas pH (pH 3.0 compared to pH 7.0) and ionic strength had no pronounced effect. At high 5-CQA/protein molar ratios, both the denaturation enthalpy and temperature of BSA increased; however, covalent bonds were created at high temperatures. The presence of 5-CQA had no effect on the solubility of BSA and alpha-lactalbumin as a function of pH, whereas it decreased lysozyme solubility at alkaline pH due to covalent interactions. These results indicate that the non-covalent interactions with 5-CQA do not have pronounced effects on the functional properties of globular proteins in food systems.  相似文献   

14.
Okara is a low‐value coproduct of soy milk production. Its dry matter contains 25–30% protein that is of high nutritive quality, has an excellent efficiency ratio, and thus holds promise for applications in food systems. However, okara protein has low solubility. We here optimized its extraction and isolation from okara by using dilute sodium hydroxide and subsequent isoelectric precipitation. The obtained okara protein isolate (OPI) was hydrolyzed with different enzymes into a range of hydrolysates with different degrees of hydrolysis. Most hydrolysates had better emulsifying activity and produced more stable emulsions than OPI. In contrast, hydrolysis had no positive effect on foam‐forming and foam‐stabilizing activity of OPI proteins. Hydrolysis of OPI enhances the emulsifying capacity of the proteins. Furthermore, the emulsifying and foam‐forming capacities of most of the OPI hydrolysates were similar to or even better than those of the commercial (soy) protein hydrolysates used in this study.  相似文献   

15.
Prolamin extracted from rice flour using 55% n-propanol contained protein impurities. Reverse phase high-performance liquid chromatography (HPLC) on a perfusion column R2/H was used to separate rice prolamin from other proteins in less than 5 min. Prolamin eluted as the major peak. The isolated prolamin migrated as a single band on sodium dodecyl sulfate polyacrylamide gel electrophoresis using a 4-12% Bis-Tris gel. Matrix-assisted laser desorption ionization mass spectrometry identified the rice prolamin as a 15 013 Da protein. The surface hydrophobicity (S(o)) of the HPLC-separated protein fractions was measured using the hydrophobic fluorescent probe PRODAN. A comparison was made with the surface hydrophobicity (S(o)) of corn prolamin and bovine serum albumin. Surface hydrophobicity values and solubility in 90% ethanol assisted in rice prolamin identification from other chromatographic peaks. The advantage of perfusion chromatography in purifying rice prolamin from other rice proteins included the reduced separation time, the speed at which the separation was carried, and the ability to regenerate the column in a short period of time and allow for more samples to be purified and separated.  相似文献   

16.
This research optimized the extraction of different protein fractions from barley grains and assessed the physicochemical properties of the fractions obtained. Pearling was first used to remove the grain's outer layers (mainly bran and germ) so that the barley cytoplasmic proteins (albumin and globulin) would be enriched in the pearling flour (PF), while endosperm proteins (hordein and glutelin) would be enriched in the pearled grain flour (PGF). Salt, alcohol, and alkaline solutions were then used to extract different barley protein fractions from PF and PGF. The effects of extraction solvent type, pH, temperature, and extraction time on protein content and extraction efficiency were studied. Aqueous ethanol (55%, v/v) efficiently extracted barley hordein from PGF at 60°C, whereas pH 11.5 alkaline solution was the most efficient for extracting both cytoplasmic and endosperm proteins from barley PF and PGF at 23°C. Subunit molecular weight, amino acid composition, and the functional properties of each isolated barley protein fraction were investigated. Barley glutelin demonstrated superior oil‐binding property and emulsifying stability, whereas barley hordein exhibited good foaming capacity.  相似文献   

17.
This study compared 38 sainfoin and 2 Lotus accessions to their respective tannin contents, N buffer solubility, and in vitro protein degradation. Tannin contents were measured by a protein precipitation method using either bovine serum albumin or Rubisco and by the colorimetric HCl/butanol method. Precipitation of bovine serum albumin and Rubisco was highly correlated (R(2) = 0.939). Correlations between the protein precipitation variants and the HCl/butanol method were relatively low (R(2) < 0.6). Protein degradation was measured at 4 h of incubation in an inhibited in vitro system and could not be explained by any of the tannin assays (R(2) < 0.03) and only partially by N buffer solubility (R(2) ≤ 0.433). Decisive factors other than the quantity of tannins or their ability to precipitate proteins must be considered. Resistance of soluble protein toward degradation can possibly be caused by tannin protein binding.  相似文献   

18.
微波对大豆蛋白氧化聚集体结构及功能特性的影响   总被引：2，自引：2，他引：0  
为了探究不同时间微波处理对大豆蛋白氧化聚集体的结构和功能性质的影响,由偶氮二异丁脒盐酸盐(2,2′-azobis (2-amidinopropane) dihydrochloride,AAPH)诱导构建大豆蛋白氧化反应体系,采用功率为350 W的微波对其照射不同时间(0、10、20、30、40、50、60、70 s),探究微波处理对氧化聚集大豆蛋白的结构特性和加工特性的影响。结果表明,氧化可诱导形成粒径、分子量更大,结构更致密的蛋白质聚集体,同时对加工特性造成损害。适当时间(<30 s)的微波处理会导致氧化聚集体的分子结构打开、粒径降低和浊度降低,无序结构减少,进而改善了起泡性、乳化性和持水、持油性。长处理时间(>30 s)的微波处理导致已解聚的大豆蛋白分子重新形成更大的分子聚集体,降低功能性质。这表明微波物理场可以通过改变大豆蛋白氧化聚集体的结构和聚集行为调节其功能性质,为大豆蛋白功能性质的改善及微波在大豆蛋白氧化聚集体行为调控的应用方面提供参考。  相似文献   

19.
《Cereal Chemistry》2017,94(3):369-376
The by‐product of rice milling (BRM), known as commercial rice bran, is the coproduct of rice processing. It is a mixture of outer layers of the grain, the embryo, and some of the starchy endosperm, and these are separated from brown rice to produce white, milled rice. This mixture contains a high concentration of protein (12–20%) in comparison with that of brown rice (7.1–8.3%) or white rice (6.3–7.1%) and is therefore an abundant and cheap protein source. Nearly 70% of the proteins in BRM are albumins and globulins, which are high in solubility, digestibility, and nutritional value. The BRM proteins are hypoallergenic and gluten‐free. With these properties, this type protein has many advantages as a unique and valuable protein source in markets such as protein supplements. The BRM protein can be extracted by physical, alkali, and enzymatic methods, which give yields ranging from 13% to more than 90%. This review highlights the opportunities and challenges in processing of BRM protein as a food ingredient.  相似文献   

20.
Brewers' spent grain (BSG) is the insoluble residue of barley malt resulting from the manufacture of wort. Although it is the main byproduct of the brewing industry, it has received little attention as a marketable commodity and is mainly used as animal feed. Our work focuses on one of the main constituents of BSG, i.e., the proteins. The lack of solubility of BSG proteins is one of the limitations for their more extensive use in food processing. We therefore aimed to generate BSG protein hydrolysates with improved technofunctional properties. BSG protein concentrate (BPC) was prepared by alkaline extraction of BSG and subsequent acid precipitation. BPC was enzymatically hydrolyzed in a pH-stat setup by several commercially available proteases (Alcalase, Flavourzyme, and Pepsin) for different times and/or with different enzyme concentrations in order to obtain hydrolysates with different degrees of hydrolysis (DH). Physicochemical properties, such as molecular weight (MW) distribution and hydrophobicity, as well as technofunctional properties, such as solubility, color, and emulsifying and foaming properties, were determined. Enzymatic hydrolysis of BPC improved emulsion and/or foam-forming properties. However, for the hydrolysates prepared with Alcalase and Pepsin, an increasing DH generally decreased emulsifying and foam-forming capacities. Moreover, the type of enzyme impacted the resulting technofunctional properties. Hydrolysates prepared with Flavourzyme showed good technofunctional properties, independent of the DH. Physicochemical characterization of the hydrolysates indicated the importance of protein fragments with relatively high MW (exceeding 14.5 k) and high surface hydrophobicity for favorable technofunctional properties.  相似文献   

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