Separation of the proteins of egg white and egg yolk and a study of their interactions in whole egg. I. Quantitative fractionation of proteins

Procedures developed for the fractionation and sub-fractionation of proteins in whole egg have been applied to separated white and yolk samples and to whole egg reconstituted from them. The fractionation pattern of whole egg soluble proteins on diethylaminoethylcellulose differed from a simple combination of the corresponding patterns for white and yolk soluble proteins. All the fractions and sub-fractions were dialysed and freeze-dried for analysis. The main effect of mixing yolk with white appears to be the conversion of some insoluble lipoproteins to a soluble form, the bulk of which has no affinity for diethylaminoethylcellulose but can be separated by chromatography on car-boxymethylcellulose into a number of fractions that have high lipid contents and are clearly derived from the low density fraction of yolk.     

The carrageenan from Iridaea undulosa B.; Analysis,fractionation and alkaline treatment

The carrageenan extracted from the seaweed Iridaea undulosa is devoid of a k-fraction and is composed of major amounts of ‘intermediate fractions’ (fractions which precipitate at potassium chloride concentrations higher than 0.125M) and lesser amounts of a ‘soluble fraction’ (soluble in 2.0M potassium chloride). It did not form gels in water or milk. The preparative fractionation of the carrageenan gave eight fractions which precipitated in narrow ranges of potassium chloride concentrations and on ultracentrifugation showed only one sharp peak. Analysis of these fractions, their infrared spectra, and the results of the periodate oxidation analysis permitted the identification of some structural units and suggested others. The alkaline treatment of the carrageenan gave a product comprising a k-fraction and a soluble fraction. The k-fraction, obtained with a high yield (53.6% of the modified polysaccharide), is capable of gelling.     

Preparation and characterization of molecular weight standards of low polydispersity from oat and barley (1→3)(1→4)-β- -glucan

Purified (1→3)(1→4)-β- -glucans (β-glucans) from oat and barley with broad molecular weight (MW) distribution were separated into seven fractions using gradient precipitation with ammonium sulfate (NH₄)₂SO₄. The MW of each fraction decreased consecutively with the concentration of (NH₄)₂SO₄ at which it was precipitated. The MW distribution of each fraction was much narrower compared to the parent sample and is comparable to commercially available pullulan MW standards. To determine whether the fractionation process was separating sub-fractions of different structure, the original β-glucan sample and each fraction were hydrolyzed by a (1→3)(1→4)-D-β-glucan-4-glucanohydrolase (lichenase, E.C.3.2.1.73) and the liberated oligosaccharides were analyzed by high performance anion exchange chromatography. The analysis revealed no differences in oligosaccharide pattern (DP 2–9) derived from each fraction and the parent sample. In particular, the tri/tetra oligosaccharide ratio remained constant for all fractions, indicating no fractionation based on structural features had taken place. The effect of starting β-glucan concentration on the fractionation process was studied. The results showed that it was possible to achieve good separation at overlapping parameter c[η] lower than 3.5. Further increase in starting β-glucan concentration hindered clear separation of the fractions. Temperature also affected the fractionation efficiency. The higher the temperature, the lower the amount of (NH₄)₂SO₄ that was necessary to precipitate the samples of same MW. A Mark Houwink relationship was derived from the measured MW and intrinsic viscosity for fractions from oat and barley, respectively.     

Antioxidant activity of the ethanolic extract from the bark of Chamaecyparis obtusa var. formosana

BACKGROUND: Chamaecyparis obtusa var. formosana (Taiwan hinoki) is an endemic conifer in Taiwan and the purpose of this study is to evaluate the antioxidant activity of various fractions obtained from the bark of this plant material. The ethanolic extract of the bark was sequentially separated into three fractions, including n‐hexane, ethyl acetate and ethanol soluble fractions, by liquid–liquid partition. Then the antioxidant activities of crude extract and three fractions along with 13 subfractions obtained from the ethyl acetate (EA) soluble fraction were tested for several antioxidant assays. RESULTS: The total phenolic content of the samples varied from 27.71 to 102.86 mg GAE g^?1 dry weight for fractions, and from 49.94 to 206.46 mg GAE g^?1 for subfractions (where GAE is milligrams of gallic acid per gram of extract). The Trolox equivalent antioxidant capacity (TEAC) ranged from 0.15 to 0.26 mmol L^?1 Trolox equivalents. The EA soluble fraction was found to be the best antioxidant‐rich fraction in terms of DPPH and reducing power assays. With further data analysis it was found that there was a positive correlation between the total phenolic content of extracts and TEAC is R² = 0.61. CONCLUSION: Results from various antioxidant assays showed that the EA fraction possessed strong antioxidant activity. This would provide additional information about the antioxidant activity of bark extract of this plant species. Copyright © 2008 Society of Chemical Industry     

Antioxidative principals of Jussiaea repens: an edible medicinal plant

Jussiaea repens L. (JRL) is an edible medicinal plant and is also used as a vegetable by the local people in southwestern China. The crude extract and its four fractions derived from JRL were evaluated for the 1,1‐diphenyl‐2‐picrylhydrazyl radical‐scavenging ability, hydroxyl radical‐scavenging capacity and the potassium ferricyanide reduction property. The ethyl acetate‐soluble fraction (EAF) and EAF6 (a subfraction derived from EAF) were the most valuable fraction and subfraction, respectively. Furthermore, bioactivity‐guided chromatographic fractionation revealed that three pure compounds greatly contributed to the antioxidant activities. Qualitative and quantitative analyses of the major antioxidant constituents in the extract were systematically conducted by NMR, mass spectral analyses and RP‐HPLC. The result demonstrated that rosmarinic acid (2.00 mg g^?1 JRL dry weight) quercetin 3‐O‐β‐d ‐glucopyranoside (9.88 mg g^?1 JRL dry weight), and kaempferol 3‐O‐β‐d ‐glucopyranoside (1.85 mg g^?1 JRL dry weight) were the major antioxidative constituents in JRL. These compounds are reported for the first time from this plant.     

Chemical and microbial evaluation of Egyptian dried egg white prepared by different techniques

Egg white was dehydrated (pan drying, spray drying) without and with glucose removal (using bacteria, yeast and enzyme). Although, moisture, protein and ether extract percentage in spray dried samples were, in general, in the same range as the imported Swiss made spray dried sample (as standard), yet the least moisture percentage was found in samples in which sugar was removed by yeast. The standard sample had the best solubility (99.79%). followed by the spray dried sample desugarized by yeast (99.67%). Samples in which Streptococcus lactis was used gave the highest percentage of insoluble matter (4.24%). Pan dried and spray dried samples were similar in solubility. The total microbial counts were found to decrease in egg white after drying (max. 4.9 × 10 org. in prepared samples, zero in the standard). Salmonella was absent in all dried samples. There are variations in the type of protein fractions of liquid egg white when the enzyme treatment or controlled bacterial fermentation were used. When yeast fermentation was used a decrease in some protein fractions was noticed in comparison with the nondesugarized sample. The dehydrated egg white proteins indicate that there was no difference between the different techniques applied for glucose removal, between drying methods and between prepared samples and imported one; 5 fractions were obtained in each sample.     

Chemical Characteristics of Low-Fat Soymilk Prepared by Low-Speed Centrifugal Fractionation of the Raw Soymilk

Abstract: Large oil–protein particles (2 to 60 μm) were found in raw soymilk (or water extract of soybean), which was prepared in specific conditions. The large particles could be separated by sedimentation by centrifuging raw soymilk for 5 to 30 min at a low gravitational force ranging from 96 to 2410 × g. Chemical analysis showed that 80% to 90% of the total lipids and 30% to 40% of the total proteins were located in the precipitated fraction. The supernatant fraction had a dramatically higher protein-to-lipid ratio than the whole soymilk. The ratio of 11S/7S proteins and the ratio of 11S acidic/basic subunits were significantly (P < 0.05) higher in the precipitate than that either in the whole soymilk or in the supernatant. Besides centrifuging conditions, other factors, including soymilk concentration, grinding method, soybean variety, and soybean storage, also significantly (P < 0.05) affected the centrifugal fractionation. This study showed that low-speed centrifugation facilitated the separation of oil-protein particles from raw soymilk, and can be used as an innovative method for preparing low-fat soymilk and 11S protein-enriched ingredients. The findings also increased our understanding of the association or aggregation between proteins and lipids in raw soymilk after grinding. Practical Application: Soymilk has become a popular beverage in the Western world due to its health benefits. Consumer demands for low-fat and organic foods have been increasing in the recent years. Currently, there are no alternative methods for manufacturing low-fat soymilk from whole soybeans. We found that most, if not all, of lipids in the raw soymilk were located in large particles, which could be separated by low-speed centrifugation. This centrifugal fractionation was investigated by varying processing parameters, soybean varieties, and soybean storage conditions. The approach has potential to be used for manufacturing low-fat soymilk. This study also has increased our understanding of the interactions between lipid and protein in raw soymilk.     

Protein Components Precipitated from Egg White by Removal of Salt

A precipitate that formed in egg white at low ionic strength affected the transparency of heat-induced gels prepared at pH 2-4 and low ionic strength. The precipitate solubilized with SDS solution containing 2-mercaptoethanol and urea included major proteins of the egg white, as shown by SDS-polyacrylamide gel electrophoresis. The bands of ovalbumin, conalbumin and other protein were smaller when the precipitate was washed with water, but lysozyme and ovomacroglobulin probably remained in the precipitate fraction. It seemed that ovalbumin, conalbumin, and other proteins co-precipitated with these two kinds of proteins. Lysozyme added to the supernatant of egg white after dialysis, did not appear to produce turbidity upon heating at pH 2.5, but whole egg white was converted to a turbid gel upon being heated at this pH.     

Emulsifying properties of soy protein isolate fractions obtained by isoelectric precipitation

Soy protein isolate (SPI) fractions were produced by isoelectric precipitation based on results of isoelectric focusing carried out on the crude soy extract. The fractions were produced from crude protein extract (pH 9.0) sequentially and non‐sequentially at isoelectric points (pIs) of 5.6, 5.1 and 4.5. Emulsions stabilised by soy proteins with pIs between 5.6 and 5.1 had the highest (P < 0.01) emulsion stability index (ESI), while those stabilised with proteins having pIs between 5.1 and 4.5 resulted in the lowest ESI for sequentially precipitated fractions. Non‐sequential fractionation at pI 5.1 produced fractions with higher emulsifying activity index (EAI) than sequential fractionation. SDS‐PAGE profiles indicated that the fractions exhibiting high functionality in terms of ESI and EAI were also richer in 7S globulin protein subunits. © 2001 Society of Chemical Industry     

Fractionation of Extracts and Crystalline and Non-Crystalline Proteins from White Kidney Beans (Phaseolus vulgaris) by Ion-Exchange High-Performance Liquid Chromatography

Sodium hydroxide solution (0.02%) and citric acid solutions (0.08N, pH 5.5, CA1; 0.60N, pH 3.5, CA2) were used to extract proteins from white kidney beans (Phaseolus vulgaris). The extracts were subjected to ion-exchange high performance liquid chromatography (IE-HPLC) using a phosphate elution buffer (20 mM, pH 7.0). The charge properties of the protein fractions present in the NaOH extract and the CA1 and CA2 extracts were similar although the relative proportion of total peak area represented by each fraction was different in the different extracts. IE-HPLC of the isoelectric precipitate (amorphous microstructure) isolated from the CA1 (bipyramidal crystalline microstructure) and the CA2 (spheroidal microstructure) extracts indicated striking differences in the charge properties of the proteins which constituted the isolates. IE-HPLC also demonstrated that the precipitation processes did not affect the charge properties of the proteins which remained after the proteins were recovered from the different extracts.     

Effect of soapwort extract on physical and sensory properties of sponge cakes and rheological properties of sponge cake batters

Soapwort extract yields relatively stable, soap-like foam in aqueous solution because of its saponin content. The objective of this study was to utilise the advantage of the high foam forming capacity of soapwort extract in the production of sponge cakes. Egg white proteins were partially replaced with soapwort extract in the sponge cake formulation. The effects of soapwort extract addition on the rheological and physical properties of cake batters and on the physical and sensory properties of sponge cakes were determined. Replacing egg white proteins with soapwort extract, up to 75% by weight, did not have any significant influence on the specific gravity of batters (p > 0.05). Addition of soapwort extract into the cake mixture did not influence the flow behaviour indices (n) of cake batters nor the consistency indices (K) of cake batters. In general, replacing egg white proteins with soapwort extracts (up to 75% by weight) did not alter physical properties of sponge cakes. Replacing egg white proteins with soapwort extract had no unfavourable influence on the sensory properties of sponge cakes. Indeed, sponge cakes formulated with soapwort extract (by replacing egg white proteins by 50% and 75% on weight basis) received significantly higher chewiness scores than did control cakes (p < 0.05). This study showed that egg white proteins could be partially replaced with soapwort extract in the formulation of sponge cakes.     

Antioxidant properties of papain hydrolysates of wheat gluten in different oxidation systems

Enzymatic hydrolysis was used for preparing hydrolysates from wheat gluten which is by-product during production of wheat starch. The enzyme used for the hydrolysis was papain. The hydrolysate was separated based on the molecular weight of the peptides by membrane ultrafiltration (UF) with a molecular weight cut-off of 5 kDa into permeate (P) and retentate (5-K) fractions. The antioxidative activities of the hydrolysate and its UF fractions were investigated by using the TBA method and scavenging effect of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. The three fractions showed strong antioxidative activities in the linoleic acid oxidation system, and exhibited DPPH radical scavenging activity. The antioxidative activity of the P fraction was almost the same as that of vitamin E at pH 7.0. The molecular weight distribution of the P fraction was concentrated in 4.2 kDa (86.5%) after gel permeation chromatography fractionation using an HPLC system.The P and 5-K fractions had higher surface hydrophobicities (H₀) at pH7.0 compared with the hydrolysate. The resulting UF fractions were superior to the hydrolysate in terms of antioxidative activities.     

Modification of Egg White Proteins with Oleic Acid

Studies on the chemical modification of egg white with oleic acid (5-50 moles/50,000g of egg white protein) revealed that the reagent partitioned equally between supernatant and precipitate. The mole ratio of oleic acid to protein in solution at the 20 mole level of treatment was 14.6:1. Oleic acid did not selectively precipitate ovalbumin, conalbumin, or lysozyme. An increase in negative charge of proteins was observed in the chromatograms of treated egg white. No difference in molecular weights of treated egg white proteins was observed. The viscosity varied with the concentration of the reagent. In cooked, frozen, and thawed egg white water retaining index was 1.5-10X greater for treated than untreated material.     

Depletion of glucose in Egyptian egg white before dehydration

Glucose was completely removed from egg white in h by using Streptococcus lactis and 0.2% yeast extract at pH 6.0 and 30 °C. A distinct objectionable odour was developed accompanied by a change in the appearance of egg white. Using Aerobacter aerogenes at pH 7.0 and 37 °C, glucose depletion was completed after 3 to 4 h depending on the initial number of bacteria used. The undesirable changes in odour and appearance of egg white were not observed. Saccharomyces cerevisiae succeeded, in presence of 0.2% yeast extract, in depleting sugar in egg white in 9 h. The optimum pH for the reaction was in the range of 6.0 to 7.5 at 32 °C. Glucose oxidase powder of fungal origin was also used for glucose depletion. Glucose was completely removed after 8 h by adding 3.8 glucose oxidase units/100 ml egg white at pH 7.3 and 14.5 °C. 1.9 and 0.95 glucose oxidase units per ioo ml egg white were not enough for complete glucose removal. No objectionable odour or undesirable changes in egg white were observed.     

New studies on gum ghatti (Anogeissus latifolia) part I. Fractionation,chemical and physical characterization of the gum

This paper describes the fractionation, chemical and physical characterization of processed gum Ghatti (Gatifolia SD), and identifies the source of its surface activity. Four fractions were separated using the gradual ethanol precipitation method. With the increase of alcohol concentration, the chemical composition of the fractions exhibited a pattern: arabinose content increased, but the galactose, protein and uronic acid contents decreased in the order of: F50 (50% ethanol precipitate), F65 (65% ethanol precipitate), F80 (80% ethanol precipitate) and FS (the supernatant after 80% ethanol precipitation). Rheologically gum ghatti and its fractions exhibited Newtonian flow behavior until gum concentrations reached to 20% (w/v), at which point gum ghatti showed some shear thinning. At the same shear rate and concentration, the apparent viscosities of these fractions decreased in the order: F50 > F65 > F80 > FS. When compared at same concentration, the FS fraction had the highest surface activity relative to the Gatifolia SD, the other fractions and even gum Arabic. Monosaccharide composition and preliminary structural analysis showed that the branching of the polymer increased in the order of F50, F65 and F80. The degree of branching levels, protein and uronic acid content could be responsible for the different solubility of the fractions in alcohol. However, the molecular structure of FS is significantly different from the other fractions. FT-IR spectroscopy revealed no esterified carboxyl group in gum ghatti. Detailed structural elucidation of each fraction will follow.     

MICROSOMAL LIPID PEROXIDAHON SYSTEM FROM HERRING LIGHT AND DARK MUSCLE: EFFECT OF CYTOSOLIC FACTORS

Soluble fractions from the light and dark muscle tissue of herring (Clupea harengus) were tested for their effect on lipid peroxidation of the isolated mierosomal fractions from the respective muscle tissues. To determine the nature of the components involved, the supernatant fractions were heated and/or dialyzed before treatment of the mierosomal fraction. In addition, some mierosomal samples were pretreated for 60 min with the supernatant fractions prior to initiating lipid peroxidation, whereas in other cases the supernatant fractions were added on initiation of the lipid peroxidation reaction. Results indicated that light muscle cytosol contained factors inhibitory to mierosomal lipid peroxidation. Dark muscle cytosol did also, but in addition appeared, to contain activators. Preheating, dialysis, or preincubation indicated the nature of some of the compound's involved. High and low molecular weight compounds were involved as were thermostable and thermolabile substances.     

Neuronal cell protective effect of aerial parts of Chinese lizard’s tail (Saururus chinensis (Lour.) Baill.)

The antioxidant and neuronal cell protective effects of silica-gel open column chromatographic fractions, obtained from Chinese lizard’s tail (Saururus chinensis) methanolic extract, were investigated. The ABTS radical scavenging and ferric reducing antioxidant power (FRAP) assays indicated that the SC4 fraction (eluted with chloroform/methanol by 4:1, v/v) obtained from Chinese lizard’s tail was more potent radical scavengers and reducing agents than that of other 5 fractions. The SC4 fraction also presented protective effects against H₂O₂-induced neurotoxicity in a dose-dependent manner. Therefore, our study suggested that the SC4 fraction has strong antioxidant and neuronal protective effects which are correlated with its high level of phenolics, particularly quercitrin and quercetin.     

Fractionation by gel exclusion HPLC of proteins from acidic and alkaline extractions of Phaseolus beans

The proteins extracted from Phaseolus vulgaris (white kidney, navy) beans and P. lunatus (baby lima, large lima) beans by sodium hydroxide (NaOH) solution and citric acid (CA) solutions were fractionated by gel exclusion high-pressure liquid chromatography. The isoelectric amorphous proteins from the NaOH extraction and bipyramidal crystalline and spheroidal proteins from the CA extractions were also fractionated. Both the NaOH and the CA extracts of the beans contained 8–10 fractions. The proteins isolated from the extracts of the P. vulgaris beans were comprised predominantly of a relatively large molecular weight fraction, regardless of the microstructure of the protein precipitate; several of the fractions which were relatively major components of the extracts were not found in the precipitates obtained from the extracts. The differences in behaviour between the extracts and protein isolates of the different beans might be related to genetic variations.     

Effect of oxidation induced by hydroxyl radical‐mediated model on molecular structural and physical character of egg white powder

The objective of this study was to determine structure and functional properties changes of oxidised egg white protein derived from hydrogen peroxide (H₂O₂)/ferric chloride (FeCl₃) /ascorbic acid hydroxyl radical‐generating systems at room temperature, including carbonyls, sulfhydryl and total sulfhydryl groups, dityrosine, free amino, surface hydrophobicity, particle size distribution, intermolecular forces, and foamability and emulsibility. Protein carbonyl and dityrosine content of egg white protein were increased (P < 0.05) with increasing the concentrations of H₂O₂. Oxidation decreased free sulfhydryl, total sulfhydryl groups and surface of hydrophobicity comparing with nonoxidised egg white protein. Oxidation also reduced its free amino content (P < 0.05). The low concentration of H₂O₂ contributing the average particle size of egg white protein was smaller than the control group. However, the high concentrations of H₂O₂ caused that egg white protein aggregated and the average particle size became larger. To sum up, oxidation made EWP denaturation and aggregation.     

Factors in Various Fractions of Meat Homogenates That Affect the Oxidative Stability of Raw Chicken Breast and Beef Loin

ABSTRACT:  The fractions of meat homogenates were analyzed to find the factors that determine the susceptibility of raw chicken breast and beef loin to lipid oxidation. The fractions used in this study were meat homogenate, precipitate, and supernatant of homogenate after centrifugation, and high and low molecular weight fractions from the supernatant. Chicken breast showed greater oxidative stability than beef loin during 10-d storage ( P < 0.05). All fractions from chicken breast showed lower amounts of free ionic iron and myoglobin and higher total antioxidant capacity (TAC) than those from beef loin during storage. The TAC level of chicken breast maintained during storage. This suggested that the oxidative stability of chicken breast was ascribed to high, stable total antioxidant capacity with low level of catalysts for lipid oxidation. The water-soluble high molecular weight fraction, which contained myoglobin, was responsible for the high lipoxygenase-like activity and lipid oxidation potential (LOP) in beef loin. TAC in all fractions from beef loin decreased during storage. This suggested that high myoglobin content in beef loin caused the imbalance between pro- and antioxidant factors leading to the high susceptibility of beef loin to lipid oxidation. Myoglobin served a major source of catalysts, ferrylmyoglobin, hematin, and/or free ionic iron, for lipid oxidation.