Molecular Structure and Functionalities of Protein Isolates Prepared from Defatted Cottonseed Flour Succinylated at Various Levels

Protein isolates were prepared from glandless cottonseed flour succinylated at various levels. Succinylation levels of the resultant proteins followed first order kinetics with respect to succinic anhydride concentration added. Succinylation decreased the amount of free sulfhydryl, as well as ξ-amino groups of proteins, but did not change intermolecular disulfide bonds. Protein isolate prepared from highly succinylated flour consisted of one homogeneous protein agglomerate, while isolate from unmodified flour contained several heterogeneous proteins. Water solubility of the isolates increased logarithmically with respect to degree of succinylation, with the sharpest increase at 95% succinylation or higher. Heat coagulability had an inverse-linear relationship with amounts of negative charges on protein molecules. Emulsion capacity and oil absorption capacity were not significantly changed at less than 60% succinylation. However, these increased markedly at greater than 60% succinylation. Emulsion capacity had a positive, but not linear correlation with water solubility of proteins.     

Investigation of Faba Bean Protein Recovery and Application to Pilot Scale Processing

Extraction and precipitation conditions were assessed for recovery of protein from dehulled faba bean flour on a laboratory scale. 10°C versus 20°C extraction did not affect solubility of nitrogenous components. However, more were extracted at pH 9 or 10 than at pH 7. Tap water extracted slightly more nitrogenous materials than 0.3M sodium chloride. Study of pH 4.0 to 5.3 for protein precipitation showed a higher yield of protein was obtained at lower pH. However, apparently simultaneous precipitation of nonproteinaceous material caused overall lower protein composition of the isolates from lower pH. Pilot scale processing of dehulled faba bean flour produced an isolate which was 92.5% protein, and represented a yield of 48% of the original protein.     

Functional Properties of Lupin Protein Isolates (Lupinus albus cv Multolupa)

Lupin protein isolates were prepared by alkaline extraction and precipitation at pH 5.1, 4.2 and 4.9 and their functional properties investigated. Solubility, emulsification capacity, swelling and gelation properties were determined under different conditions of pH, ionic strength and heat treatment. Lupin protein isolates showed better solubility than soybean isolate and a similar emulsification capacity. Swelling and gelation were found to be inferior, but when modifications in the methods of isolate preparation were introduced these properties were significantly improved. Consequently, it is possible to consider lupin proteins as a potential substitute for soybean proteins in food applications.     

Tepary Bean Flour, Albumin and Globulin Fractions Functional Properties Compared with Soy Protein Isolate

The solubilities of teparies albumin (TA) and globulin (TG) compared to soy protein isolate (SPI) were higher at pH 1–4 but similar at pH 8–12. Although SPI developed significantly higher viscosity than the tepary bean proteins, the flour (TF) and TA had significantly higher heat coagulability and foaming properties. TG did not coagulate upon heating (100°C). Also, TG formed a weaker and less stable foam and had significantly lower emulsion capacity than TF, TA, and SPI. Tepary bean proteins absorbed significantly higher amounts of fat (corn oil) than SPI.     

Effects of succinylation and deamidation on functional properties of oat protein isolate

The effects of two different modification methods (deamidation and succinylation) on the functional properties (solubility, water- and oil-binding capacity, foaming capacity and stability, emulsion activity and stability) of oat protein isolates were evaluated. Protein isolates extracted from defatted oat flour at alkaline pH were acylated by 0.20 g/g of succinic anhydride. The protein isolate was also modified using a mild acidic treatment (HCl, 0.5 N). Succinylation and deamidation improved solubility and emulsifying activity of the native protein isolate. Foaming capacity of oat protein isolate increased after deamidation, whereas succinylation decreased it. The deamidated and succinylated proteins had lower foam and emulsion stabilities than had their native counterpart. Water- and oil-binding capacity, in both modified oat proteins, was higher than those of the native oat protein isolate.     

Kinetics of Nitrogen Solubility Loss in Heated Flour and Protein Isolates From Bean, Phaseolus vulgaris

The effect of temperature, time and moisture content on the loss of nitrogen solubility of heated bean flour and protein isolates was studied. Solubility loss followed first-order reaction kinetics in almost all cases studied. The rate of solubility loss was greatly increased with increasing moisture content both for flour and protein isolates; protein isolate was far more sensitive to heat treatment than the flour. Activation energies for the first-order reaction constants were calculated and ranged between 20–30 kcal/mole.     

Functional properties of raw and heat processed cashew nut (Anacardium occidentale, L.) kernel protein isolates

The functional properties viz. solubility, water and oil absorption, emulsifying and foaming capacities of the protein isolates prepared from raw and heat processed cashew nut kernels were evaluated. Protein solubility vs. pH profile showed the isoelectric point at pH 5 for both isolates. The isolate prepared from raw cashew nuts showed superior solubility at and above isoelectric point pH. The water and oil absorption capacities of the proteins were slightly improved by heat treatment of cashew nut kernels. The emulsifying capacity of the isolates showed solubility dependent behavior and was better for raw cashew nut protein isolate at pH 5 and above. However, heat treated cashew nut protein isolate presented better foaming capacity at pH 7 and 8 but both isolates showed extremely low foam stability as compared to that of egg albumin.     

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.     

Comparison of Protein Extraction Solutions for Rice Starch Isolation and Effects of Residual Protein Content on Starch Pasting Properties

Protein extraction solutions such as aqueous solutions of sodium hydroxide (0.1 and 0.2 %), sodium lauryl sulfate (SLS, 1.2 %) containing sodium sulfite (0.12 %), and dodecylbenzene sulfonate (DoBS, 1.2 %) containing sodium sulfite (0.12 %) were compared in their protein removal efficiencies during isolation of starch from a rice flour (Ilpumbyo, a nonwaxy Korean rice variety). In addition, the pasting properties of the isolated starch was compared. More than 80 % of the flour protein was extracted in 1 h by stirring the dispersion (1:3, w/v) at room temperature. Repeating the extractions (1 or 2 h for each step) with fresh solution significantly increased the protein removal efficiency. When the extraction in 0.2 % NaOH was repeated four times (1 h for each step) at 25°C, the residual protein content in the isolated rice starch was 0.9 % (DB), equivalent to 86 % removal of the rice protein. Raising the extraction temperature slightly increased the protein solubility, but starch loss also became significant. Among the solutions, DoBS was most effective in removing rice protein whereas SLS was least. The residual protein content had a critical role in determining the pasting characteristics of the isolated starch, showing a negative correlation to the peak viscosity of the starch paste, but a positive correlation to the pasting temperature.     

花生湿热处理对其分离蛋白的结构和功能特性的影响

本文通过还原/非还原电泳、热差示扫描、表面疏水性及等电点测定等手段,表征了花生湿热处理对其分离蛋白结构和功能特性的影响.结果表明:在105℃随着湿热处理时间延长其分离蛋白中伴球蛋白所占比例逐渐减少,球蛋白在加热75min后产生热聚集,此外通过美拉德反应生成的糖蛋白含量逐渐增加,分离蛋白等电点向酸性偏移,表面疏水性先逐渐...     

Functional Properties of Lupin Seed (Lupinus mutabilis) Proteins and Protein Concentrates

Functional and electrophoretic properties of the seed flour and a protein concentrate prepared by alkaline extraction from lupin seeds (Lupinus mutabilis, cultivar H-6) were investigated. SDS-PAGE indicated presence of 13 and 12 subunits in the seed flour proteins and the protein concentrate, respectively. Lupin protein concentrate had good water and oil absorption and gelation properties. Solubility of lupin proteins was minimum at a pH of 4.0 but increased rapidly beyond pH 5.0. Foaming capacity of the protein concentrate could be improved by increasing concentration as well as by adding NaCl and was influenced by pH and incorporation of certain carbohydrates. Emulsion properties of lupin proteins were concentration and pH dependent. Moist heat improved the in vitro digestibility of the seed proteins. The seed flour as well as the protein concentrate did not have detectable trypsin, chymotrypsin, and α-amylase inhibitory activities.     

Effects of Heat Processing on the Functionality of Whey Protein Concentrates

The effects of heat processing on the composition and functionality of whey protein concentrations (WPC) were investigated. WPC was manufactured from milk, whey and retentate that had either been pasteurized at 72°C for 15 sec or had received no heat treatment. Eight combinations of heat treatment were utilized. Pasteurization of the milk had a positive effect on overrun and foam stability, but a negative effect on gel strength at pH 6.5, protein hydrophobicity, and neutral lipid content. Pasteurization of the whey resulted in decreased mineral content bud did not affect functionality. Pasteurization of the retentate caused a decrease in emulsion capacity, soluble β-lactoglobulin, solubility, whipped topping overrun and gel strength at pH 8.0.     

Extractability and functional properties of some legume proteins isolated by three different methods

The extraction of protein from the flour of three grain legumes (faba beans, chick peas and fenugreek) was investigated using three different methods. Three protein preparations were made: by alkaline extraction and precipitation at isoelectric pH (protein isoelectric precipitate, PIP); extraction with 0.5 M sodium chloride solution and precipitation by ionic strength reduction (protein micellar mass, PMM); extraction in aqueous or saline solution in the presence of pepsin or pancreatin (partially hydrolysed protein preparation, PHP). Two of the protein isolates had higher values of water absorption and fat absorption compared to their corresponding parent flours, with fenugreek being the exception. Oil emulsification of the isolates was in the descending order: PMM, PHP and PIP. The PHP isolate had the highest nitrogen solubility index (NSI) values at pH 2.4 followed by PMM at pH 5.7–6.4 and finally PIP at pH 4.5–5.5.     

Solubility and Water Absorption of Systems Containing Soy Protein Isolates, Salt and Sugar

Solubility and water absorption of three soy protein isolates in the presence of sodium chloride and sucrose were studied. Water absorption also was investigated in a system that contained wheat flour in addition to the isolates, salt and sugar. Sodium chloride affected nitrogen solubility index and water absorption of the isolates; sucrose did not. Similarly, sodium chloride affected water absorption in the flour-soy system, whereas sucrose did not. An apparent inverse relationship was observed between water absorption of soy protein isolates in the absence of flour and in combination with flour. Dough development times were shorter and doughs were less stable for flour-isolate mixtures than for flour alone.     

Emulsifying Capacity and Emulsion Stability of Soy Proteins Compared with Corn Germ Protein Flour

Both emulsifying capacity (EC) and emulsion stability (ES) increased with increasing concentrations from 0.4% to 0.8% of soy flour (SF), soy concentrate (SC), soy isolate (SI) and corn germ protein flour (CGPF) when studied by response surface methodology. EC and ES increased as pH increased from 6 to 8 in all samples. Increasing incubation temperatures of protein solutions from 20–70°C or from 4–20°C did not affect EC or ES, respectively. SF had the highest EC, followd by SI, SC, and CGPF.     

Characterization of Soy Protein Concentrate Produced by Membrane Ultrafiltration

The functionality of membrane processed soy concentrate was very similar to soy flour in terms of solubility and water hydration capacity. The high emulsifying activity index of soy flour is believed to be reflective of its higher solubility, while surface hydrophobicity is believed to be responsible for an equally high emulsifying activity index in acid precipitated soy isolate. The proteins of soy flour and membrane soy concentrate seem to have most of their hydrophobic residues buried in the interior, while they are exposed in acid precipitated soy isolate. Heating resulted in a decrease in solubility but improved the hydration capacity and emulsifying activity of both soy flour and membrane soy concentrate. The essential amino acid profile of concentrate was comparable to current commercial isolates manufactured by acid precipitation. The majority of the polypeptides present in soy flour were observed to be present in the concentrate. The membrane soy concentrate was determined to have the least soybean aroma when compared to both soy flour and acid precipitated soy isolate.     

Production and Evaluation of Pea Protein Isolate

Laboratory and pilot plant processes were developed for producing pea protein isolate from field peas. Sodium proteinate and isoelectric products containing up to 90% protein were obtained by alkaline extraction and precipitation at the isoelectric point. Drying was carried out by freeze, spray and drum processes. Chemical analysis, functional properties, color and flavor of the dried isolates compared favorably with their soy counterparts. Generally, the sodium proteinates exhibited more functionality than isoelectric isolates. Drum drying decreased the nitrogen solubility index and increased water absorption. Freeze- and spray-drying resulted in isolates with the highest emulsification and water absorption values. Spray drying produced the best foaming, color and flavor properties.     

热诱导大豆蛋白纤维聚集体的分离及性质研究

酸性热处理条件下,随着大豆分离蛋白(SPI)自发形成纤维聚集体,仍有部分未自组装聚集的多肽分子存在其中,二者比例对蛋白功能性质产生较大影响。本文以超滤手段对热诱导大豆蛋白纤维聚集体和多肽进行大量分离,确定分离方法并研究两者的理化性质。结果表明:100 ku超滤膜反复分离两次即能获得较好的分离效果;SPI经热处理后,其等电点溶解度提高,但中性p H下溶解度变小,且蛋白水解致使其表面电位绝对值明显提高;分离所得纤维聚集体的氨基酸组成和表面电位与热处理蛋白相似,在等电点和中性p H溶解度更低;多肽则含有较少疏水氨基酸和较多负电氨基酸,在p H 2.0~9.0溶解度较好,其在酸性p H下电荷量和静电排斥力较低,导致其以无定形聚集体的形式存在,而中性p H其电荷量较高导致多肽分子间相互作用减弱,聚集体解离。     

火麻仁蛋白的提取分离及理化性质研究

以脱脂火麻仁粉(defatted hemp seed meal,HPM)为原料,采用两种方法进行火麻仁蛋白(hemp seed protein isolate,HPI)的提取分离,碱提/酸沉法制备得到碱提蛋白(hemp seed protein isolate-alkaline extraction,HPI-AE),盐溶/盐析法制备得到盐提蛋白(hemp seed protein isolate-salt extraction,HPI-SE)。HPI-SE的蛋白含量(94.8%)高于HPI-AE的蛋白含量(85.9%);并且HPI-SE的外观色泽更加亮白。蛋白质凝胶电泳(sodium dodecyl sulfate polyacrylamide gel electrophoresis,SDS-PAGE)结果表明,两种方法提取的火麻仁蛋白主要成分均为火麻仁球蛋白,二者氨基酸组成相似,均含有丰富的精氨酸。不同pH值条件下,HPI的溶解性曲线均呈U型,但是在相同pH值条件下,二者的溶解性存在较大的差异。火麻仁蛋白的起泡性和蛋白质的溶解性呈现出正相关,当pH值远离等电点时,同种电荷的静电斥力提高了蛋白质的溶解性,从而改善了蛋白质的起泡性。荧光光谱显示,在不同pH值条件下,HPI的蛋白构象不随pH值变化发生明显改变,但HPI-SE的荧光强度高于HPI-AE的荧光强度,显示HPI-SE的蛋白质聚集程度高于HPI-AE。     

Protein and gossypol extractability from cottonseed flour

The extractability of protein and free-gossypol from fully gossypolised cottonseed flour was investigated. The various parameters studied include (i) effect of pH (ii) effect of salts and (iii) the combined effect of pH and salts. The results indicated that it is possible to obtain a protein isolate free from free-gossypol by alkaline extraction at pH values of 9 and 10. Highest protein extraction (57%), highest protein recovery (96%) and highest protein content of the precipitate (75%) occurred at pH 10. In general, dilute aqueous electrolytes did not accomplish significantly higher extracta-bilities although they resulted in comparatively lower free-gossypol contents in the protein precipitate. However, with 1.0m CaCl2 protein extraction was 75% but both protein recovery (61%) and the protein content of the precipitate (61%) was comparatively low. Extraction in the presence of salts and alkali did not improve protein extractability and gave a protein isolate high in free-gossypol content.