Walnuts (Juglans regia L): proximate composition,protein solubility,protein amino acid composition and protein in vitro digestibility

Walnuts contained 16.66% protein and 66.90% lipids on a dry weight basis. Non‐protein nitrogen values ranged from 6.24 to 8.45% of the total nitrogen when the trichloroacetic acid concentration was varied within the range 0.25–1.0 M . Albumin, globulin, prolamin and glutelin respectively accounted for 6.81, 17.57, 5.33 and 70.11% of the total walnut proteins. Walnut proteins were minimally soluble at pH 4.0. The majority of total walnut protein polypeptides had estimated molecular weights in the range 12 000–67 000. The Stokes radius of the major protein in walnuts (glutelin fraction) was 66.44 ± 1.39 Å. Lysine was the first limiting essential amino acid in total walnut proteins as well as in the globulin and glutelin fractions. Leucine and methionine plus cysteine were the second limiting essential amino acids respectively for the prolamin and albumin fractions. Hydrophobic and acidic amino acids dominated the amino acid composition in all protein fractions. Native and heat‐denatured walnut glutelins were easily hydrolysed by trypsin, chymotrypsin and pepsin in vitro. © 2000 Society of Chemical Industry     

Amino acid profiles and quality from lotus seed proteins

BACKGROUND: Protein composition, amino acid profile and nutritional value of the lotus seed and its Osborne fractions were investigated. The seed was rich in protein with 19.85%, and showed well balanced amino acid composition compared with FAO/WHO pattern, Its nutritive properties were similar to those observed in the reference soybean protein. Phenylalanine, tyrosine, leucine and lysine were the limiting amino acids in the seed proteins. The albumin and globulin were the main protein fraction, the amino acid profile and nutritional value were close to the seed protein. RESULTS: Changes in transition temperature and thermal stability were observed through different solvent extractions. Albumin possessed the predominant thermal stability (81.4 °C) followed by globulin (74.49 °C), prolamin (69 °C) and glutelin (65.6 °C). So, solvent compositions influence the profile of AAs and their nutritive value, and aqueous solvent with 0.1 mol L^?1 NaCl was an efficient protein solubiliser. CONCLUSION: The results indicated that the extraction processes influenced the lotus seed protein quality and thermal stability. Overall, the study revealed that the lotus seed protein was nutritionally well‐balanced protein and might be of significant importance in the formulation of diets for humans. © 2012 Society of Chemical Industry     

Extractability and Chromatographic Characterization of Wheat (Triticum aestivum L.) Bran Protein

About 70% of the protein for human consumption is derived from plants, with cereals as the most important source. Wheat bran protein has a more balanced amino acid profile than that of flour. We here for the first time report the amino acid, size exclusion, and SDS‐PAGE profiles of bran Osborne protein fractions (OPFs). Moreover, we also investigated how OPFs are affected when physical barriers which entrap proteins in bran tissues are removed. Albumin/globulin is the most abundant OPF. It is richer in lysine and asparagine/aspartic acid than other OPF. Most bran albumin/globulin proteins have a molecular weight (MW) lower than 30 k and their chromatographic profiles differ from those of flour. The prolamin has high levels of proline and glutamine/glutamic acid. It is rich in proteins with a MW of 30 to 45 k and about 66 k reflecting contamination with gliadin from endosperm. The glutelin has high levels of glycine, proline, and glutamine/glutamic acid. Its protein is of intermediate and high MW with little protein with MW lower than 30 k. The high (MWs from 80 to 120 k) and low (MW around 45 k) MW glutenin subunits of flour are also present in bran. The glutelin of wheat endosperm is named glutenin. Ball milling releases albumin/globulin and glutelin but not prolamin. Not all glutelin was endosperm glutenin as a substantial part was entrapped in the aleurone cells.     

Fractionation and characterization of tartary buckwheat flour proteins

Protein fractions (albumin, globulin, prolamin and glutelin) were extracted from defatted tartary buckwheat flour. Albumin was the predominant protein fraction (43.8%) followed by glutelin (14.6%), prolamin (10.5%), and globulin (7.82%). Albumin was relatively rich in histidine, threonine, valine, phenylalanine, isoleucine, leucine and lysine. Globulin had high levels of methionine and lysine. Prolamin was high in histidine, threonine, valine, isoleucine, and leucine. Glutelin was rich in histidine, threonine, valine, isoleucine, and leucine. SDS–PAGE analysis, under non-reductive and reductive conditions, showed that disulfide bonds existed in the four fractions. Non-reduced albumin showed major bands at 64, 57, 41, and 38 kDa, and globulin at 57, 28, 23, 19 and 15 kDa. Reduced albumin and globulin shared two common bands at 41 and 38 kDa. Reduced prolamin showed major bands at 29, 26, 17 and 15 kDa. In vitro pepsin digestibility of the four fractions (from high to low) was: albumin > globulin > prolamin and glutelin.     

Japanese barnyard millet (Echinochloa frumentacea): Protein content,quality and SDS–PAGE of protein fractions

Total protein from five varieties of Japanese barnyard millet (Echinochloa frumentacea,) was separated into albumin/globulin, prolamin and glutelin fractions. The protein fractions were examined by sodium dodecylsulphate polyacrylamide gel electrophoresis. Total protein of the varieties ranged from 110·5 to 139·3 mg g^?1 of which 11·3–17·2% was albumin/globulins, 6·8–9·3% prolamins, 7·5–11·6% prolamin–like, 5·9–9·1% glutelin-like and 39·3–54·4% true glutelins. Amino acid analyses of the total protein showed that the varieties had essentially the same ammo acid composition. With the exception of lysine the amino acid levels adequately matched the provisional FAO scoring pattern. The amino acid composition of the protein fractions was also very similar. Electrophoretic analysis showed that the albumin/globulin fraction contained three or four components; the prolamin and glutelin fractions each had five components. The glutelin fraction had higher molecular weight components than the other two fractions.     

萝卜籽粕蛋白质的组成及功能性质

以萝卜籽粕为原料,提取了其中的蛋白质;根据溶解性,萝卜籽粕蛋白中的清、球、谷、醇溶蛋白被分 离;用氨基酸自动分析仪测定了萝卜籽粕蛋白的氨基酸组成;物理化学方法测定萝卜籽粕蛋白的功能性质以及体外 清除1,1-二苯基-2-三硝基苯肼自由基、?OH、NO2 －、H2O2的能力。结果表明：萝卜籽粕蛋白中球、谷、清和醇溶蛋 白含量分别占总蛋白质的44%、33%、21%和2%;萝卜籽粕蛋白含18 种氨基酸,第一限制氨基酸为蛋氨酸,其氨基 酸评分为57。萝卜籽粕蛋白具有很好的功能性质及抗氧化能力,表明有很高的开发价值。     

热变性大米蛋白的结构和性质研究Ⅰ米蛋白加热前后的溶解特性和氨基酸变化

为探讨热变性米蛋白的性质与结构关系,分析了大米蛋白加热前后的溶解性能和氨基酸组成变化。结果表明,米渣中各种蛋白质的含量大大低于未受高温处理的原料大米;米渣蛋白中胱氨酸含量比大米谷蛋白提高83%,说明大米醇溶蛋白、球蛋白和清蛋白等受热后也存在于米渣中;米渣谷蛋白胱氨酸含量比米渣蛋白降低23%,说明胱氨酸是影响米渣蛋白溶解的重要因素。     

NUTRITIONAL EVALUATION OF BEAN (PHASEOLUS VULGARIS) PROTEIN. IN VIVO VERSUS IN VITRO PROCEDURE

Digestibility (D), Biological Value (BV) and Net Protein Utilization (NPU) of whole bean flour and of the protein fractions glutelin (GLU), globulin (GLO), globulin GI (GI), albumin (ALB) and a protease inhibitor/lectin rich fraction (PIL) were determined, after autoclaving (121C, 15 min). For the whole bean flour both in vivo and in vitro procedures were used. For the in vivo assay a nitrogen balance with rats was performed. In vitro evaluation was based on the mean essential amino acid index (MEAAI) and in vitro protein digestibility. Results for the whole bean flour (BF) showed no statistical differences (p ≤ 0.01) between in vivo and in vitro techniques. In vitro digestibility ranged from 75–93% for the protein fractions and was 76% for the whole bean protein; biological value for the protein fractions ranged from 62–79%, and was 85% in the whole bean protein; calculated NPU ranged from 47–76% for the fractions, and was 65% for the whole bean protein.     

PROTEIN EXTRACTABILITY, FRACTIONATION AND AMINO ACID COMPOSITION OF SOME LEGUMINOUS SEEDS FOUND IN NIGERIA

Protein content in eight minor legume seeds grown in Nigeria was determined, and protein was fractionated into albumin, globulin, prolamin and glutelin. Seed protein concentrates (SPC) were prepared from legume seeds; and extractabilities of protein N, total N content, yield and the amino acid profiles are reported. The globulins and glutelins were the major fractions. Mucuna seeds (velvet bean) appear to be the most promising species for obtaining SPC based on the high values for extractability of SPC, protein N and total N. Amino acid composition shows that the sulfur‐containing amino acids, methionine + cysteine, were the most limiting amino acids in the seed proteins. Lysine content (9.12 g/100 g) of Mucuna seeds was high. Prosopis africana (mesquite bean) contains remarkably high levels of methionine and lysine (3.55 and 6.50 g/100 g protein, respectively), which make it a good potential supplement to the starchy tuber and cereal diets of the local population. It was concluded that Milletia thonningii, Adenanthera pavonina (coral seeds), Lonchocarpus sericeus and Mucuna seeds have a promising potential as sources of low‐cost protein for possible use as food/feed supplements.     

Preparation and characterization of high‐quality rice bran proteins

Rice bran contains 120–200 g kg^?1 protein in addition to a large amount of fat, carbohydrate, and phytic acid. Rice bran protein (RBP) fractions were refined by a two‐step preparation to eliminate residual carbohydrate. The first step involved the sequential extraction of defatted rice bran into RBP fractions using their distinct solubility to give 37 g kg^?1 of albumin, 31 g kg^?1 of globulin, 27 g kg^?1 of glutelin, and 2 g kg^?1 of prolamin. In the second step, carried out by dissolving in respective solvent and isoelectric precipitation, the protein content of each fraction increased from 69% to 97% for albumin, from 71% to 90% for globulin, from 74% to 83% for glutelin, and from 18% to 20% for prolamin. The low protein content in the prolamin fraction might be due to its low solubility in the protein assay. Emulsifying stability index and surface hydrophobicity increased in the second‐step preparation of albumin and globulin, but not of glutelin. Emulsifying properties of RBPs were lower than that of a soybean protein isolate. Denaturation temperatures and enthalpy values of denaturation for albumin, globulin, glutelin, and prolamin were 50.1 °C/1.2 J g^?1, 79.0 °C/1.8 J g^?1, 74.5 °C/3.0 J g^?1, and 78.5 °C/8.1 J g^?1, respectively. No significant differences in the denaturation temperatures and enthalpy values of denaturation of RBP fractions were obtained with these two‐step preparations (P < 0.05). Copyright © 2007 Society of Chemical Industry     

Effects of gamma irradiation on edible seed protein,amino acids and genomic DNA during sterilization

This work describes radiation-induced effects on edible seed protein profiles, carbohydrates, amino acids and genomic DNA during gamma sterilization. The total protein and carbohydrate was decreased with increasing dose compared to control samples. Oryzasativa L. Cv-2233 exhibited a minimum effect in terms of its loss in total soluble protein content, compared to other seeds at 6 kGy, and the soluble protein fraction, containing 14–16 kDa albumins and 22 kDa globulin, was unchanged up to 6 kGy. In Cicer arietinum, the effect of gamma rays was more pronounced on albumin and prolamin with respect to glutelin and globulin. The easy-to-digest and difficult-to-digest proteins were not significantly affected up to 4 kGy. However, the soluble free amino acids of all the seeds increased with increasing dose. The total DNA content and band intensities both decreased with increasing absorbed dose; however, the band positions were unchanged for all seed types.     

Purification and characterization of antioxidative peptides derived from rice bran protein hydrolysates

Rice bran protein fraction (RBPF)—albumin, globulin, glutelin and prolamin were hydrolyzed with proteases M, N, P, S and pepsin under their optimal conditions for 24 h. Hydrolysates of various hydrolysis periods were collected and subjected to peptide mapping and the antioxidative activity measured by the 2,2-Azino-bis-3-ethylbenzothiazoline-6-sulfonic Acid (ABTS) method. Protease M hydrolysates showed high degree of hydrolysis (DH), but low antioxidative activity. On the contrary, pepsin hydrolysates showed low DH with high activity. Albumin and globulin hydrolysates had higher DH values, but lower values for glutelin and prolamin. The globulin hydrolysate (Opep2) from 2 h-pepsin hydrolysis was separated by using three consecutive purification steps with RP-HPLC. Nineteen antioxidative peptides were isolated and their amino acid sequences were determined by a gas-phase protein sequencer and MALDI-TOF mass spectrometry. These peptides were composed of 6–30 amino acid residues with molecular masses ranging from 670–3,611 Da. Tyr-Leu-Ala-Gly-Met-Asn had the highest antioxidative activity among them.     

米胚蛋白组分的提取及功能性质研究

采用Osborne的方法,从米胚中提取清蛋白、球蛋白、醇溶蛋白和谷蛋白,4种蛋白中谷蛋白的含量最高,占72.69%,其余3种蛋白的含量相差不大;考察4种蛋白的溶解性得出,在pH5下4种蛋白的溶解性最低,随着pH的增大或减小,溶解性逐渐增加,且清蛋白和球蛋白的溶解性较醇溶蛋白和谷蛋白高;在pH11、0.1mol/L NaCl浓度、1mg/mL蛋白浓度下,加入3mL大豆油,4种蛋白的乳化活性及乳化稳定性均达到最大值。     

Isolation of a novel peptide from silkworm pupae protein components and interaction characteristics to angiotensin I-converting enzyme

The hydrolysate of silkworm protein produced by acid protease (Asperqiius usamii NO. 537) contains angiotensin I-converting enzyme inhibitory activity. Four kinds of protein components were identified in silkworm pupae protein, albumin, globulin, prolamin and glutelin, and the albumin was in the highest quantity. The four component proteins were then further hydrolyzed by acid protease under the same conditions, and the hydrolysate of albumin was determined with the highest ACE inhibiting effect, followed by globulin. Albumin could be easily hydrolyzed under the aqueous conditions, and the overall albumin protein content was higher than the other three protein components. The peptide sequence “APPPKK” was determined by LC–MS/MS separation and X!Tandem software identification. The peptide inhibitory activity was 0.047 mg/mL in IC₅₀. The peptide was bonded to Asp⁴¹⁵, Asp⁴⁵³, Thr²⁸², His ³⁵³, Glu¹⁶² in hydrogen bond to ACE active pocket by flexible docking calculations. This study indicates that silkworm pupae protein may be a suitable candidate to explore functional foods with anti-hypertension bioactivity.     

Fractionation and biochemical characterization of moth bean (Vigna aconitifolia L.) proteins

Moth bean seeds contained 24 g/100 g protein (micro-Kjeldahl N×6.25) on a dry weight basis. Among the solvents tested, 0.1 mol/l NaOH and 0.1 mol/l sodium phosphate buffer (pH 7.5) were the most effective in solubilizing the seed flour proteins. Native isoelectric focusing of the total soluble proteins indicated moth seed proteins to be acidic (pI range 4.55-<6.55) with a few neutral to alkali proteins (pI range 7.35-9.3). Globulin fraction dominated the seed protein composition accounting for ∼64 g/100 g of the total soluble proteins in the seeds. The globulin fraction was composed of at least three major glycopeptides with an estimated molecular mass range of 45-55 kDa and several additional polypeptides in the 14-32 kDa range. Sulfur amino acids were the first limiting amino acids in the seed flour proteins. Native and heat denatured albumin and glutelin fractions were readily hydrolysed, in 30 min, by pepsin at 37 °C. Although resistant to proteolysis in the native state, heat denatured globulin (100 °C, 30 min, boiling water-bath) was completely digested to <14 kDa polypeptides by pepsin in 30 min at 37 °C. Moth bean was devoid of detectable phytohemagglutinating activity and had low trypsin inhibitory activity when compared with the corresponding activities in soybeans.     

Chemical investigation of Erythrina variegata Linn. seed proteins

Proteins were extracted from deoiled seeds of Erythrina variegata Linn., a potential source of non-conventional seed, in aqueous solutions of various pHs or by different concentrations of NaCl, KCl, CaCl₂ and MgSO₄ at pH 7.0. Nitrogen contents of the seeds and deoiled seeds showed good protein content. Fractionation of protein was done to separate albumin, globulin, prolamine and glutelin. Amino acid analysis of the total protein isolates (TPI) and the fractions isolated (except prolamine) identified 17 amino acids, most of which were essential. The molecular weights of TPI and the fractions were determined by SDS–PAGE electrophoresis. The results showed that TPI was composed of twelve bands, eight for globulin, nine for prolamine and six for glutelin. Studies on surface structure of the proteins and seed flour by scanning electron microscopy (SEM) are also included.     

Changes in gross chemical composition with emphasis on lipid and protein fractions during germination of fenugreek seeds

Germination of fenugreek seeds for 3 and 5 days increased moisture, crude protein, crude fibre, non-protein nitrogen and ash contents, but total lipids and carbohydrates were decreased. Marked increases of Na and P, as well as Mg and Zn were observed. Triacylglycerols decreased continuously and this was accompanied by an increase in free fatty acids, monoglycerides, sterolesters and polar lipids. Albumin was the major protein fraction followed by globulin, glutelin and prolamin. Germination increased glutelin and non-protein nitrogen; the other fractions were decreased. The protein in vitro digestibility was improved after germination. PAGE showed a marked dissociation of albumin and globulin fractions after germination.     

Composition of Cicer soongaricum seeds

The legume, Cicer soongaricum grows wild in high altitude regions of the Himalayas. The seeds are nutritionally rich, containing 19.1% protein, 44.5% starch, 7.2% oil and 3.4% minerals. Glutelin has been found to be the major protein fraction (43.7%) whereas albumin, globulin and prolamin are 11.5, 14.3 and 6.6%, respectively. The oil contains 29.8% phospholipids, wherein palmitic (30.0%), stearic (32.4%) and linolenic acids (13.6%) are the major fatty acids. The phospholipid fraction has an appreciable content of phosphatidyl choline (1.0% in the seed) which is higher than in soya bean, presently the commercial source of its manufacture.     

Isolation,fractionation, and some chemical studies on Kleinhovia hospita Linn. seed protein

Protein was extracted from the seeds of Kleinhovia hospita Linn., which is being a nonconventional source. Extraction of K. hospita seed protein at various pH values in aqueous solution and at pH 7, different salt concentrations were done. Fractionation of protein from seeds was performed to separate albumin, globulin, prolamin, and glutelin. The amino acid compositions of total protein isolate (TPI) and the fractions were determined. A total of 15 amino acids were identified including 9 essential amino acids. Gel filtration by Sephadex G-100 revealed the presence of three components in the TPI. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis analysis of TPI and fractions showed different polypeptide bands having molecular weights ranging from 12 to 42 kDa approximately. Scanning electron microscopic study of TPI and fractions revealed the surface topology of the protein.     

Characterisation and functional properties of watermelon (Citrullus lanatus) seed proteins

BACKGROUND: People in developing countries depend largely on non‐conventional protein sources to augment the availability of proteins in their diets. Watermelon seed meal is reported to contain an adequate amount of nutritional proteins that could be extracted for use as nutritional ingredients in food products. RESULTS: Osborne classification showed that globulin was the major protein (≥500 g kg ^?1) present in watermelon seed meal, followed by albumin and glutelin. Sodium dodecyl sulfate polyacrylamide gel electrophoresis indicated that the polypeptides had low molecular weights ranging from 35 to 47 kDa. Isoelectric focusing revealed that the isoelectric point of most proteins was in the acidic range 4–6. These proteins are rich in aspartic acid, glutamic acid and serine. An increase in pH (5–9) significantly (P < 0.05) decreased the denaturation enthalpy of these proteins. Among functional properties, albumin exhibited a much higher dispersibility index (810.3–869.6 g kg^?1) than globulin (227.8–245.4 g kg^?1), glutelin (182.1–187.7 g kg^?1) and prolamin (162.3–177.7 g kg^?1). Digestibility was in the ranges 760.6–910.0 and 765.5–888.5 g kg^?1 for Mateera and Sugar Baby watermelon protein fractions respectively, while surface hydrophobicity ranged from 126.4 to 173.2 and from 125.8 to 169.3 respectively. The foaming and emulsifying properties of albumin were better than those of the other proteins studied. CONCLUSION: The good nutritional and functional properties of watermelon seed meal proteins suggest their potential use in food formulations. Copyright © 2010 Society of Chemical Industry