Studies on egg albumen and whey protein interactions by FT-Raman spectroscopy and rheology

Analysis of Adhesion at the Interface of Steamed Bread and Eggshell

The adhesion phenomenon of polymers occurs in nature and in human activity. In the present paper, an adhesion system of steamed bread and eggshell was observed in formation when steamed bread and eggshells were placed in close contact and cooled slightly in the ambient air. The adhesion phenomena and mechanism of the adhesion interface between the steamed bread and eggshell were investigated and systematically discussed. Strong-bond interfaces were observed by scanning electron microscope (SEM). The formation process and mechanism of the strong-bond adhesion were also analyzed molecular dynamics simulation technology, and the results are discussed. The simulation analyses showed that the starch molecules at the calcite (104) crystal face were diffused in a water vapor environment, and the formation and solidification of multiple hydrogen bonds in the starch chain and oxygen atoms in the calcium carbonate were observed in detail during cooling. The diffusion rate of hydrogen atoms in hydroxyl groups on the calcite surface decreased gradually with the decrease of the cooling temperature of the steamed bread's upper surface. The strong adhesion of the steamed bread and eggshell is attributed to the synthetic effect of the absorption, diffusion, surface chemistry, and the formation of multiple hydrogen bonds between the starch from the steamed bread and the calcium carbonate crystals in eggshell. The interesting findings are helpful for the design of strong bonds, and provide an idea for new environmentally friendly adhesive materials.

Konjac glucomannan improves the gel properties of low salt myofibrillar protein through modifying protein conformation

Improving the characteristics of low salt proteins is the key to the gel properties of low-salt meat products which are demanded by people nowadays. The present study focused on the effects of KGM concentrations on the changes in structure and gelling properties of low-salt myofibrillar protein (MP). KGM addition (≤0.75 %) irrespective of salt concentration modified secondary and tertiary structures of MPs, enhanced the binding capacity of Troponin-T and Tropomyosin, augmented the gelling behavior of proteins, and remarkably improved the storage modulus (G') and gel strength of heat-induced MP gels. Interestingly, KGM addition in low salt condition showed the transformation of the all-gauche SS conformation into gauche-gauche-trans and trans-gauche-trans, and the partial transformation of α-helices into β-sheets. overall, KGM modified the structure of low salt MPs and thus improved the gel properties of low salt MPs. Therefore, KGM is recommended for low-salt meat processing to enhance the MP gelling potential.

Rheological properties of dairy desserts: Effect of rice bran protein and fat content

Rice bran protein (RBP) is an alternative plant protein that can be used in a wide range of foods due to its unique functional, nutritional, and hypoallergenic properties. The interactions of RBP with other biopolymers have revealed its feasibility for application in dairy products such as whipped cream and dairy desserts. Therefore, the effects of RBP and fat content on the rheological properties of dairy desserts were investigated. The pH value was not influenced by protein, but the nonfat milk solid content was changed by fat and protein content. All the desserts showed thixotropic properties which were mainly related to the molecular disentanglement at high shear rates. By increasing fat like RBP, the apparent viscosity (η_a ) was increased. Rheological parameters such as n value, thixotropic index, storage (G'), and loss moduli (G'') were increased by RBP. Moreover, the dairy desserts containing RBP and whole milk presented generally higher G', G'', complex modulus, and complex viscosity values, and lower tan δ values. The RBP enriched samples also had a higher hardness and gumminess. Syneresis was decreased by RBP, which was related to the formation of ordered mesh-like structures which enabled the entrapment of more water. There was a positive correlation between the rheological, textural, and physical properties of the dessert with added RBP, and therefore dairy dessert attributes can be improved along with fat reduction. However, a sensory evaluation is needed to unravel the acceptability rate of RBP in fat reduction from the view point of consumers. PRACTICAL APPLICATION: Rice bran protein (RBP) has nutritional and hypoallergenic properties which enable it to apply to many products such as dairy desserts. One of the main concerns in dairy technology is the growing interest in low-fat products due to health problems. RBP showed unique properties which makes the creamy behavior. The rheological results have elucidated the creaminess associated with RBP and can assist in the proper simulation of mouthfeel.

Effect of high hydrostatic pressure on activity, thermal stability and structure of horseradish peroxidase

The mechanism of the high hydrostatic pressure (HHP) effect on horseradish peroxidase (HRP) is still unclear. The activity, thermal stability and structural changes of HRP after HHP treatments were studied in this work. Compared with the untreated sample, the enzyme activity reduces by 36% after 800 MPa processing. The results indicated that the conformation of the enzyme active center changes under pressure. Furthermore, HHP also changes the conformation of disulfide bonds and some secondary structures in HRP. These structural and conformational changes induce decreased activity. In addition, differential thermal scanning (DSC) results showed that the thermal denaturation temperature decreased from 103.74 °C to 85.78 °C after pressure treatment, suggesting HRP molecules formed large aggregates after pressure treatment. In this study, the interaction mechanism between pressure and enzyme was studied as well, and the results can provide some guidance for the application of HHP technology in fruit and vegetable products processing.

Cloning, characterisation and expression of the SERPINB14 gene, and association of promoter polymorphisms with egg quality traits in layer chicken

1. Ovalbumin (SERPINB14) is the most abundant protein present in egg white contributing about 54% of the total egg protein. In this study, the objectives were to clone and characterise the coding sequence of the SERPINB14 gene, to explore its expression profile, identify polymorphisms in the promoter of the gene and explore any association with egg quality traits in White Leghorn chickens.2. SNPs and mRNA expression of SERPINB14 in White Leghorn chicken lines were detected by PCR-single strand conformation polymorphism (SSCP) along with sequencing and qPCR. The open reading frame (ORF) was cloned in an expression plasmid vector and sequenced.3. The ORF of this gene was 1161 bp encoding a peptide of 386 amino acids. There were three SNPs observed in the coding region of the gene, one of which was of the mis-sense type, having c562G>A transition which resulted in substitution of alanine to threonine at position 188 in the protein sequence. In both the lines, an increase in expression of the gene was observed after onset of egg production with peak expression at the 40^th week of age compared to before onset of lay. The SERPINB14 gene was expressed in the magnum, but not in ovary and infundibulum, tissues of each White Leghorn line. The promoter region of the gene showed SNPs with three haplotypes; H1, H2, and H3. The haplo groups were associated with the egg weight and age at sexual maturity in the IWI line and Haugh unit and albumin index in the IWK line.4. It was concluded that the ORF of SERPINB14 gene in White Leghorn chicken lines is polymorphic. The promoter region of the gene is also polymorphic and has significant (P < 0.05) association with Haugh unit and egg weight in IWK and IWI chicken lines, respectively.

Quantifications of Oleocolloid Matrices Made of Whey Protein and Oleogels

Consumer demand for high protein content and plant-based fat has necessitated novel approaches to healthy food products. In response to this need, oleogels (OG) (structured liquid oils) emerged as a possible means of not only replacing saturated and trans fats but also delivering food protein. Nevertheless, an in-depth view of the structure of networks made of OG and protein is deficient. Hence, the objective of this study is developing oleocolloid (OC) (whey protein and rice bran wax OG) and hydro-oleocolloid (HOC) (OC + water) matrices with varying protein content (2.5–7.5%) to characterize their structural properties. Thermal analysis of the matrices via differential scanning calorimetry (DSC) documented the effects of hydrophobic interactions on the protein structure and its stability. Whey protein denaturation temperature increased from 74.9 °C to 102.8 °C in the presence of high oleic soybean oil. The effects of vegetable oil on WPI structure was also verified by FTIR spectroscopy. Data analysis revealed slight structural changes of the WPI secondary structure in the hydrophobic oil medium and the α-helix and β-sheet proportion in the emulsion medium was significantly altered. Similar analysis was performed in OC and HOC networks to quantify possible interactions between protein and rice bran wax. Results indicated that the protein was denatured during the thermal and mechanical conditions required for the oleogelation process, while it did not affect the systems’ solid fat content (SFC) and polymorphic patterns of the oleogels. However, DSC analysis showed different onset of melting for OC and HOC samples due to colloidal interactions between the protein and the lipid phase. The role of these chemistry was confirmed by microscopy analyses where OC and HOC matrices displayed notably different microstructural properties. The observed differences in the structural properties between OC and HOC matrices indicate the different colloidal interactions mediated by oleogelation process and the liquid medium type (oil vs. emulsion).

Physicochemical and antibacterial properties of fabricated ovalbumin–carvacrol gel nanoparticles

The applications of carvacrol are limited due to its poor stability, water solubility and high volatility. Herein we fabricated ovalbumin–carvacrol gel nanoparticles and then improved solubility, stability and antibacterial property of carvacrol.

Gelation of food protein-protein mixtures

Gelation of proteins is one of the principal means to give desirable texture to food products. Gelation of individual proteins in aqueous solution has been investigated intensively in the past, but in most food products the system contains mixtures of different types of proteins. Therefore one needs to consider interaction between different proteins both before and during gelation. Most food proteins can be classified as globular proteins, but casein and gelatin are also important food proteins. In this review the focus is on gelation induced by heating or cooling, which is the most commonly used method. After briefly discussing general features of protein aggregation and gelation, the literature on gelation of mixtures of different types of globular proteins is reviewed as well as that of mixtures of globular proteins with gelatin or with casein. The effect on the gel stiffness and the microstructure of the gelled mixtures will be discussed in terms of different scenarios that can be envisaged: independent aggregation and gelation, co-aggregation and phase separation.

RNA-Seq reveals seven promising candidate genes affecting the proportion of thick egg albumen in layer-type chickens

Eggs with a much higher proportion of thick albumen are preferred in the layer industry, as they are favoured by consumers. However, the genetic factors affecting the thick egg albumen trait have not been elucidated. Using RNA sequencing, we explored the magnum transcriptome in 9 Rhode Island white layers: four layers with phenotypes of extremely high ratios of thick to thin albumen (high thick albumen, HTA) and five with extremely low ratios (low thick albumen, LTA). A total of 220 genes were differentially expressed, among which 150 genes were up-regulated and 70 were down-regulated in the HTA group compared with the LTA group. Gene Ontology (GO) analysis revealed that the up-regulated genes in HTA were mainly involved in a wide range of regulatory functions. In addition, a large number of these genes were related to glycosphingolipid biosynthesis, focal adhesion, ECM-receptor interactions and cytokine-cytokine receptor interactions. Based on functional analysis, ST3GAL4, FUT4, ITGA2, SDC3, PRLR, CDH4 and GALNT9 were identified as promising candidate genes for thick albumen synthesis and metabolism during egg formation. These results provide new insights into the molecular mechanisms of egg albumen traits and may contribute to future breeding strategies that optimise the proportion of thick egg albumen.

Characterization of zein assemblies by ultra-small-angle X-ray scattering

Zein, a major corn protein, has an amphiphilic molecule capable of self-assembling into distinctly different structures, i.e., rods, sheets, and spheres. In this work, ultra-small-angle X-ray scattering (USAXS) was applied to investigate the formation of self-assembled zein structures in binary solvent systems of ethanol and water. The study included observing structural changes due to aging. Three distinctive regions, each corresponding to different co-existing structures having a hierarchical organization, were observed in zein-solvent systems. Rod shaped (R_g = 1.5-2.5 nm, P = 1) primary structural units were identified, believed to be molecular zein. Two-dimensional sheet-like structures (R_g = 80-200 nm, 2 < P < 3) were observed, believed to be formed by primary units first assembled into one-dimensional fibers and then into 2D sheet structures. Also, large three-dimensional spherical aggregates were observed (R_g > 1000 nm, P = 4), believed to have assembled from two-dimensional sheet structures. Aging did not change the size or the shape of the primary units, but USAXS detected changes in R_g and P values of the intermediate structures, pointing to a further level of self-assembly where proteins develop a more regular and organized structure. The viscoelastic moduli (G' and G''), the consistency index (K) and the flow behavior index (n), were also measured to investigate the effect of zein structural development by self-assembly on rheological behavior. Samples became more solid-like with aging. Raman spectra suggested that zein underwent secondary structure transformations from α-helix to β-sheets, which influenced the size and morphology of molecular assemblies and ultimately the rheological properties of zein solutions.

Prediction of heat-induced polymerization of different globular food proteins in mixtures with wheat gluten

Egg, soy or whey protein co-exists with wheat gluten in different food products. Different protein types impact each other during heat treatment. A positive co-protein effect occurs when heat-induced polymerization of a mixture of proteins is more intense than that of the isolated proteins. The intrinsic protein characteristics of globular proteins which enhance polymerization in mixtures with gluten are unknown. In this report, a model was developed to predict potential co-protein effects in mixtures of gluten and globular proteins during heating at 100°C. A negative co-protein effect with addition of lysozyme, no co-protein effect with soy glycinin or egg yolk and positive co-protein effects with bovine serum albumin, (S-)ovalbumin, egg white, whole egg, defatted egg yolk, wheat albumins and wheat globulins were detected. The level of accessible free sulfhydryl groups and the surface hydrophobicity of unfolded globular proteins were the main characteristics in determining the co-protein effects in gluten mixtures.

Rheology and microstructure of binary mixed gel of rice bran protein-whey: effect of heating rate and whey addition

BACKGROUND

Rice bran protein (RBP) is a valuable plant protein which has unique nutritional and hypoallergenic properties. Whey proteins have wide applications in the food industry, such as in dairy, meat and bakery products.

RESULTS

Whey protein concentrate (WPC), RBP and their mixtures at different ratios (1:1, 1:2, 1:5 and 1:10 w/w) were heated from 20 to 90 °C at different heating rates (0.5, 1, 5 and 10 °C min(-1) ). The storage modulus (G') and gelling point (Tgel ) of WPC were higher than those of RBP, indicating the good ability of WPC to develop stiffer networks. By increasing the proportion of WPC in mixed systems, G' was increased and Tgel was reduced. Nevertheless, the elasticity of all binary mixtures was lower than that of WPC alone. Tgel and the final G' of RBP-WPC blends were increased by raising the heating rate. The RBP-WPC mixtures developed more elastic gels than RBP alone at different heating rates. RBP had a fibrillar and lentil-like structure whose fibril assembly had smaller structures than those of WPC.

CONCLUSION

The gelling structure of the mixed gel of WPC-RBP was improved by adding WPC. Indeed, by adding WPC, gels tended to show syneresis and had lower water-holding capacity. Furthermore, the gel structure was produced by adding WPC to the non-gelling RBP, which is compatible with whey and can be applied as a functional food for infants and/or adults. © 2015 Society of Chemical Industry.

Development of a gluten-free rice noodle by utilizing protein-polyphenol interaction between soy protein isolate and extract of Acanthopanax sessiliflorus

BACKGROUND

The potential of the protein-polyphenol interaction was applied to crosslinking reinforced protein networks in gluten-free rice noodles. Specifically, inter-component interaction between soy protein isolate and extract of Acanthopanax sessiliflorus fruit (ogaja) was examined with a view to improving its quality.

RESULTS

In a components-interacting model system, a mixture of soy protein isolate (SPI) and ogaja extract (OE) induced a drastic increase in absorbance at 660 nm by haze formation, while the major anthocyanin of ogaja, cyanidin-3-O-sambubioside, sparsely interacted with SPI or gelatin. Individual or combined treatment of SPI and OE on rice dough decreased all the viscosity parameters in rapid visco analysis. However, SPI-OE treatment significantly increased all the texture parameters of rice dough derived from Mixolab(®) analysis (P < 0.05). Incorporation of SPI in rice dough significantly reduced endothermic ΔH, and SPI-OE treatment further decreased this value. SPI-OE interaction significantly increased the tensile properties of cooked noodle and decreased 53.7% of cooking loss compared to the untreated rice noodle.

CONCLUSION

SPI-OE treatment caused a considerable reinforcement of the network as shown by reducing cooking loss and suggested the potential for utilizing protein-polyphenol interaction for gluten-free rice noodle production.

Dispersive and FT-Raman spectroscopic methods in food analysis

Raman spectroscopy is a powerful technique for molecular analysis of food samples.

Effect of Pulsed Electric Field on Microstructure of Some Amino Acid Group of Soy Protein Isolates

The effect of a pulsed electric field (PEF) on the microstructure of some amino acids was studied. Raman spectrum was used to determine the effect of PEF on tyrosine, tryptophan, proline residues, histidine, arginine, aliphatic amino acid, disulfide bond, and polypeptide backbone in soy protein isolates (SPI). Results suggested that increasing the intensity of PEF gradually to 50 kV cm−1 led to a reduction in gauche C–S conformation of CCSSCC dihedral angles. The increase of the PEF intensity caused an increase in the gauche–gauche–gauche conformation of the disulfide bond accompanying a decrease in α-helix and β-sheet and an increase in antiparallel β-sheet and disorder structure. A critical pulse intensity of 30 kV cm−1 was observed for unfolding and reassembling of SPI, which was verified in our previous study (Liu et al., Eur Food Res Technol 233:841–50). When the pulse intensity gradually increased to around 30 kV cm−1, the exposure of tyrosine and tryptophan, the vibration of CH2 wagging in proline and CH2 in the midazole ring of histidine, the vibration of C—H bending and C—N stretching inside a charged arginine, and asymmetric H—C—H bending deformation vibration in CH2 and CH3 groups in aromatic and aliphatic amino acids gradually increased, suggesting an unfolding of protein molecules. When the pulse intensity continually increased from 30 to 50 kV cm−1, the microstructure of all above amino acids decreased due to the reassembly of unfolding proteins.

The self-assembly, aggregation and phase transitions of food protein systems in one, two and three dimensions

The aggregation of proteins is of fundamental relevance in a number of daily phenomena, as important and diverse as blood coagulation, medical diseases, or cooking an egg in the kitchen. Colloidal food systems, in particular, are examples that have great significance for protein aggregation, not only for their importance and implications, which touches on everyday life, but also because they allow the limits of the colloidal science analogy to be tested in a much broader window of conditions, such as pH, ionic strength, concentration and temperature. Thus, studying the aggregation and self-assembly of proteins in foods challenges our understanding of these complex systems from both the molecular and statistical physics perspectives. Last but not least, food offers a unique playground to study the aggregation of proteins in three, two and one dimensions, that is to say, in the bulk, at air/water and oil/water interfaces and in protein fibrillation phenomena. In this review we will tackle this very ambitious task in order to discuss the current understanding of protein aggregation in the framework of foods, which is possibly one of the broadest contexts, yet is of tremendous daily relevance.

Raman spectroscopic characterization of structural changes in heated whey protein isolate upon soluble complex formation with pectin at near neutral pH

The mechanism leading to an alteration of heat aggregation of whey protein isolate (WPI) in the presence of pectin was investigated by assessing structural changes of proteins using Raman spectroscopy. WPI solutions were heated without or with pectin at 0.015-0.2 pectin to WPI weight ratios and pH 6.0-6.4. In the absence of pectin, thermal denaturation resulted in a loss of α-helical structure and an increase in β-structure and random coils of protein. At pH 6.0 and 6.2, heat aggregation of WPI was suppressed when pectin (0.05-0.15 pectin to WPI ratios) was present as shown by a decrease in turbidity and particle size. Concomitantly, changes in the secondary structures were reduced, indicating the enhanced stability of protein structure by pectin. Raman results also revealed that α-helix and β-sheet are dominant structures in heated WPI--pectin soluble complexes, and hydrogen bonding between biopolymers increased. The effect of pectin was pH dependent, indicating the involvement of electrostatic interaction.