Functional Properties Of Proteins Research Articles

Extraction Optimization, Functional and Thermal Properties of Protein from Cherimoya Seed as an Unexploited By-Product.

Plant-based proteins are gaining in attraction compared with animal-based proteins due to their superior ethical profiles, growing concerns on the part of various organizations about animal health and welfare, and increased global greenhouse-gas emissions in meat production. In this study, the response surface methodology (RSM) using a Box-Behnken design (BBD) was applied to optimize the ultrasound-assisted alkaline extraction of cherimoya-seed proteins as valuable by-products. The effects of three pH, temperature, and time factors on the protein-extraction yield and protein content were investigated. The pH at 10.5 and temperature of 41.8 °C for 26.1 min were considered the optimal ultrasound-assisted alkaline-extraction conditions since they provided the maximum extraction yield (17.3%) and protein content (65.6%). An established extraction technique was employed to enhance the cherimoya-seed protein yield, purity, and functional properties. A thermogravimetric analysis (TGA) of the samples showed that the ultrasound-assisted alkaline extraction improved the thermal stability of the protein concentrate.

Application of Solid-State Fermentation for the Improving of Extruded Corn Dry-Milling By-Products and Their Protein Functional Properties.

In this study, the effect of solid-state fermentation (SSF) with Lactobacillus sakei MI401 and Pediococcus acidilactici PA-2 strains on functional properties of extruded (130 °C; 25 rpm) corn-milling by-products (CMB) and their albumin, globulin, and prolamin fractions was evaluated in order to produce stabilized and functionalized food/feed stock. Extrusion resulted in a considerable reduction of microbial contamination of CMB by five log cycles, increased damaged starch, water-absorption capacity, and lowered protein and fat contents by 12.4% and 37%, respectively. The application of SSF for the extruded CMB have been shown to improve the water absorption, foaming, and emulsifying capacity of albumins and globulins and also increased the digestibility and free radical scavenging activity of prolamins. The essential amino acid content (EAA) in CMB and antioxidant activity of prolamins was lowered after extrusion but significantly increased after SSF. The combination of the abovementioned treatments can be confirmed as a prospective functionalization of CMB, capable of potentially enhancing its safety and improving nutritional, biochemical, and technological properties of proteins.

Drying methods affect physicochemical and functional characteristics of Clanis Bilineata Tingtauica Mell protein.

Clanis Bilineata Tingtauica Mell Protein (CBTMP) was a kind of natural full-price protein which has a bright application prospect in the food industry. Since the functional properties of protein can be significantly affected by drying method, this study aims to explore the effect of different drying methods, namely freeze drying (FD), vacuum drying (VD),and hot-air drying (HD) on the structure and functional properties of CBTMP. The results showed that the degree of oxidation of CBTMP was found to be in the following order: HD > VD > FD. Functional characteristics revealed that the CBTMP prepared by VD had relatively high foaming ability (150.24 ± 5.34°C) among three drying methods. However, the stability of emulsion and rheological properties prepared by FD was superior to other samples. Differential scanning calorimeter (DSC) showed CBTMP made by HD had the relatively good thermal stability (Tp = 91.49 ± 0.19 °C), followed by VD and FD. Digestive properties reflected that heating treatment could significantly increase its degree of hydrolysis in vitro. To sum up, the research could provide experimental guidance and theoretical support for the preparation method and utilization of CBTMP.

Oxidation-mediated structure and molecular interaction transformation of egg white protein: The underlying mechanism of functional properties and in vitro gastric digestibility improvement

In this paper, the effects of hydroxyl radical-induced oxidation on structural characteristics, molecular interaction, functional properties, especially in gastric digestibility of egg white protein (EWP) were investigated. Altogether, oxidation enhanced EWP foaming stability, accompanied with even and loose arrangement bubbles by high interfacial and rheological properties. Additionally, structure and morphology characterization of hydrolysates as well as digestion kinetics results indicated the oxidized EWP had greater digestion degree and rate to release more free amino acids, along with hydrolysates composed by smaller globules and fibers. Briefly, oxidation might improve EWP functional and gastric digestive properties by providing more flexible conformation and strengthening non-covalent interactions. This work might provide an enlightening insight for enhancing protein functional properties and the nutrition of EWP via prompting amino acids release for the healthy food design.

Storage impact on egg white powder's physical and functional properties.

Changes in storage temperature and time alter the functional properties of egg white powder (EWP) and determine its quality and shelf-life, finally affecting the consumer acceptance of the products made from EWP. In the present study, the EWP samples were stored at four different temperatures (-20, 4, 25 and 37 °C) for 60 days, and then the protein structural, physical and functional properties of EWP were measured and assessed further for correlation with storage conditions using heatmap. The viscosity of the EWP solution increased after 30 days. Foaming ability and rheological properties increased first and then decreased compared to untreated samples with the prolonged storage time. Correlation analysis results indicated that the gel hardness, water holding capacity, foaming ability, emulsifying ability, particle size, dispersibility and viscosity of EWP were significantly related to storage time (P < 0.05). Only the gelation properties of EWP stored at 37 °C for 60 days changed significantly and were negatively related to its moisture content (P < 0.05). Additionally, the random coil content of EWP was positively correlated with particle size, moisture content, solubility and gel properties, whereas β-sheet was negatively correlated with them. Compared to other temperatures, the functional properties of EWP were relatively stable under 4°C. Therefore, the low temperature (4°C) was selected as the most suitable storage temperature for EWP. The results of the present study could provide a theoretical basis for the shelf-life extension of EWP. © 2022 Society of Chemical Industry.

Covalent interaction of soy protein isolate and chlorogenic acid: Effect on protein structure and functional properties

Covalent interaction of soy protein isolate (SPI) and chlorogenic acid (CA) through laccase catalysis was studied. The structure, interfacial properties (foaming and emulsifying properties) and antioxidant activities of soy protein isolate-chlorogenic acid (SPI-CA) adducts were characterized. The formation of covalent adducts was indicated by the result of the SDS-PAGE analysis. The UV–vis and FTIR analysis indicated that the addition of CA resulted in changes in the secondary structure of the protein. The spectroscopy analysis indicated that the structure of SPI tended to unfold. The emulsifying activity of SPI-CA80 (CA concentration is 80 μmol/g protein) adducts was the highest, which increased by 34.77%. Additionally, SPI-CA100 adducts exhibited high antioxidant capacity, with ABTS and DPPH radical scavenging rates increased by 24.83% and 14.41%, respectively. The results showed that the interfacial properties of SPI were correlated with changes in the concentration of CA. Overall, this study demonstrates that covalent binding of SPI to CA enhances the potential application of SPI as a functional ingredient in food.

Chemical composition, nutritional evaluation and functional properties of Elaeagnus mollis Diels (Elaeagnus L.) seeds

AbstractBackgroundElaeagnus L. seeds have high amount protein and are an important food source for humans. The chemical composition of Elaeagnus mollis Diels (Elaeagnus L.) seeds and the biochemical, nutritional, and functional properties of Elaeagnus L. seeds protein isolate (PPI) and protein fractions were studied, which is essential to the exploration of new protein sources.ResultsThe results indicated that Elaeagnus L. seeds contained 50.87% oil and 36.27% protein. Elaeagnus L. seeds oil was rich in unsaturated fatty acid (91.7%), especially linoleic acid, oleic acid and linolenic acid and ω‐6/ω‐3 was 6.33, closest to FAO/WHO recommended ratio. Alkali protein fraction (APF, 49.82%) was predominant and was rich in Glu, Arg and Pro. Water‐soluble protein fraction (WPF) had the highest SRC of 75.35, followed by PPI (70.66). The essential amino acids of PPI and WPF compared well with FAO/WHO recommended pattern for adults (except Lys and Trp). Functional properties of proteins were found to be comparable with soybean protein isolate. Low antinutritional factors enable the utilization of the proteins in nutrition food formulations.ConclusionThis study could be beneficial for enabling the utilization of Elaeagnus L. seeds proteins in nutrition and health‐related food formulations.

Effect of microwave treatment on the structural and functional properties of proteins in lentil flour

Microwave is the commonly adopted thermal technology for the cooking and other industrial processing of lentils. The study focused on evaluating the effect of microwave treatment (MT) on the protein profile and functional properties of lentil flour (LF). The lentils with 18% moisture content were exposed to MT at three different power levels (540, 720, and 900 W) and exposure times (2, 4, and 6 min). The treated lentil flour samples were defatted before further studies. The results revealed that the MT positively impacted most of the desired functional properties like water and oil absorption capacity and emulsion properties; also, MT has an insignificant effect on foaming capacity, and significantly reduced the foaming stability from 80.25% to 60%. The structure of the MT flours differed from the untreated counterparts, and MT improved the functional properties of lentil flour. Protein secondary structural changes were observed in MT flour. It was observed that MT altered the crystalline and amorphous natures of the LF, implying that MT is appealing as an alternative emerging technology to improve the functional and quality parameters of lentil proteins with potential applications for other pulse proteins.

Covalent bonding between polyphenols and proteins: Synthesis of caffeic acid-cysteine and chlorogenic acid-cysteine adducts and their quantification in dairy beverages

Protein-polyphenol interactions affect the structure, stability, and functional properties of proteins and polyphenols. Oxidized polyphenols (o-quinones) react rapidly with the sulfhydryl group of cysteine (Cys) residues, inducing covalent bonding between proteins and polyphenols. However, quantitative data on such reactions remain elusive, despite the importance of depicting the significance of such interactions on food structure and function. This work reports the synthesis, purification, and characterization of caffeic acid-cysteine (CA-Cys) and chlorogenic acid-cysteine (CGA-Cys) adducts and their stable isotope analogs, CA-[13C3,15N]Cys and CGA-[13C3,15N]Cys. A sensitive LC-MS/MS isotope dilution method was developed to simultaneously quantify these adducts in foods and beverages. Protein-bound CA-Cys and CGA-Cys were detected in the micro-molar range in milk samples with added CA and CGA, confirming covalent bonding between milk proteins and CA/CGA. These adducts were detected in commercial coffee-containing beverages but not in cocoa-containing drinks. Furthermore, the adducts were found to be partially stable during enzymatic protein hydrolysis.

Application of definitive screening design to optimization of the protein extraction and functional properties of proteins in Auricularia auricula.

Auricularia auricula (A. auricula) is one of the most abundant sources of plant protein in edible fungi. Problems of low protein yield exist in traditional methods of protein extraction such as alkali extraction and ultrasonic-assisted alkali after pretreatment with enzymes. Thus, the protein extraction process was investigated and optimized using a definitive screening design from A. auricula to improve the protein yield under practical operating conditions of temperature, the concentration of NaCl, meal/water ratio, extraction time and pH. The yield of protein isolates of the isoelectric-ammonium sulfate precipitation (9.34% w/w) was obtained almost three times and the protein content (55.23% w/w) was approximately 1.6 times that of the traditional extraction method of isoelectric precipitation. Next, the optimized method was successfully applied to the analysis of the functional properties of the protein. A. auricula protein isolate (AAPI) had better solubility, emulsification and foaming capacity than soy protein isolate (SPI) and pea protein isolate (PPI), and the oil holding capacity of AAPI exhibited extremely well, which was approximately five times that of SPI and six times that of PPI. The texture properties of AAPI gel were similar to those of PPI gels. AAPI extracted by the optimized method had a satisfactory yield and had the potential to substitute plant-originated proteins in food processing. © 2022 Society of Chemical Industry.

Cassava starch and chickpea flour pre-treated by microwave as a substitute for gluten-free bread additives.

There is an increasing demand for gluten-free products, which are regularly made by a combination of ingredients and additives. Microwave pre-treatment of gluten-free ingredients is an alternative to food additives because it may induce changes in protein and starch functional properties. In this context, this study aimed to apply microwave treatment in cassava starch and chickpea flour, analyzing their functional and thermal properties and their ability to substitute additives in gluten-free breads, comparing them to an additive-containing bread. All formulations were analyzed regarding their physical characteristics and quality parameters. The microwave-treated ingredients showed color, thermal properties and morphology changes. The bread made with chickpea flour treated with initial moisture of 40% showed the best quality parameters when compared to the control bread. The ingredients pre-treated with microwave have shown efficiency on gluten-free bakery additives substitution, allowing the use of a clean label terminology.

Influence of the fractionation method on the protein composition and functional properties

Mild wet fractionation can separate pea proteins into a soluble and a non-soluble fraction. Soluble proteins and solutes are extracted into the soluble protein fraction, insoluble proteins are collected in the non-soluble protein fraction. The protein composition in the respective fractions was investigated by further fractionating the protein fractions with isoelectric precipitation. The molecular mass of the proteins in the fractions was determined by SDS-PAGE and size exclusion chromatography. The protein fractions' solubility was determined in excess water, and the gelation properties were investigated at the same protein concentration. With mild wet fractionation, compared to conventional wet fractionation, both globulins and albumins are extracted. The protein fractions were mixtures of both proteins, although the non-soluble protein fraction contained mainly globulins. Solubility and gelation properties varied with protein type, composition and protein state; isoelectric precipitation decreased the gelation capacity of the protein fractions.

Extraction and properties of glutinous rice bran protein obtained by the mild alkaline extraction for the bran combined with enzymatic treatment for the residues

AbstractThe mild alkali extraction combined with the enzymatic hydrolysis was explored to extract protein from glutinous rice bran in the study, and the function properties of the proteins were investigated. The mild alkali extraction of pH 5.0 and temperature 50°C was carried out firstly for the water‐soluble protein extraction from the bran at the solid–liquid ratio of 1:10 (w/v) for 3.0 h, and the complex enzyme of cellulase and papain (7:3, w/w) were subsequently added to hydrolyze the residue for a better protein yield. After a mild proteolysis treatment under the conditions of enzyme addition 5.0%, pH 6.0, temperature 55°C and time 4.5 h, the final 90.2 ± 0.22% protein yield was obtained. It was interesting that the DPPH radical scavenging activity of the IC50 0.71 mg/ml was significantly improved, meanwhile, based on the combined extraction strategy, the protein solubility, emulsifying, and foaming properties were significantly enhanced in a wide range of pH environments. These results demonstrated that the mild alkali extraction combined with the enzymatic hydrolysis could be used in the glutinous rice bran protein extraction with high yield and good functionality, and the extracted protein could be potentially applied in food industry as nutraceutical ingredient or as the functional ingredient in the commercialized food products.Novelty impact statementAlthough the glutinous rice bran has an abundance of protein content, the protein has not been well extracted yet to be utilized in the food industry. Therefore, the proper procedure needs to be explored for glutinous rice bran protein extraction. The mild alkali combined with the enzymatic hydrolysis was firstly applied in the study, and the protein yield of glutinous rice bran protein was notably improved, furthermore, the antioxidant and function properties of glutinous rice bran protein also have been significantly increased because of the mild extraction and proteolysis.

PLP_FS: prediction of lysine phosphoglycerylation sites in protein using support vector machine and fusion of multiple F_Score feature selection.

A newly invented post-translational modification (PTM), phosphoglycerylation, has shown its essential role in the construction and functional properties of proteins and dangerous human diseases. Hence, it is very urgent to know about the molecular mechanism behind the phosphoglycerylation process to develop the drugs for related diseases. But accurately identifying of phosphoglycerylation site from a protein sequence in a laboratory is a very difficult and challenging task. Hence, the construction of an efficient computation model is greatly sought for this purpose. A little number of computational models are currently available for identifying the phosphoglycerylation sites, which are not able to reach their prediction capability at a satisfactory level. Therefore, an effective predictor named PLP_FS has been designed and constructed to identify phosphoglycerylation sites in this study. For the training purpose, an optimal number of feature sets was obtained by fusion of multiple F_Score feature selection techniques from the features generated by three types of sequence-based feature extraction methods and fitted with the support vector machine classification technique to the prediction model. On the other hand, the k-neighbor near cleaning and SMOTE methods were also implemented to balance the benchmark dataset. The suggested model in 10-fold cross-validation obtained an accuracy of 99.22%, a sensitivity of 98.17% and a specificity of 99.75% according to the experimental findings, which are better than other currently available predictors for accurately identifying the phosphoglycerylation sites.

Extraction, conformation characteristics and functional properties of soybean lipophilic proteins

Elucidation of soybean lipophilic protein (SLP) structural characteristics and functional properties would enhance its application. This study aimed to optimize the extraction and investigate the structural properties of SLP extracted from soybean meal with high oil concentration. Additionally, soybean lipophilic protein was compared to extracted SPI, 11S and 7S to promote its potential utilization. The results revealed that, under the optimal conditions defined using the response surface methodology, the yield of soybean lipophilic protein was (11.8%). Meanwhile, compared with other soybean proteins, SLP showed the highest phospholipids concentration (12.1%). Moreover, structural analyses showed that SLP had higher α-helix and β-sheet contents, a more compact tertiary conformation, and better thermal stability than SPI, 11S, and 7S. Soybean lipophilic protein also showed a high fat-holding capacity, good foaming, and emulsifying properties but low protein solubility and viscosity. The results suggested that soybean lipophilic protein can be used in various food and nutraceutical formulations.

Utilization of fermented and enzymatically hydrolyzed soy press cake as ingredient for meat analogues

The aim of the present study was to improve the properties of soy press cake to be utilized as an ingredient of meat analogues. Soy press cakes were fermented with lactobacillus strains, and separately hydrolyzed by cellulase/xylanase mixture and α-amylase. Meat analogues were produced with 10% fermented or hydrolyzed soy press cakes. The effect of applied processes on protein oxidation, physical and functional properties of soy press cakes were analyzed, as well as sensory and textural properties of meat analogues. The results indicated that soy press cake was a suitable source of fibre and energy with low content of saturated fatty acids, and provided plant-based proteins and essential amino acids. The study demonstrated the potential of lactic acid fermentation, and enzymatic hydrolysis to improve water- and oil-holding capacity and reduce protein oxidation in soy press cakes. L. acidophilus 336 and cellulase/xylanase mixture were recommended for fermentation and hydrolysis of soy press cakes, respectively, regarding reduction of protein oxidation. Fermentation of soy press cakes with L. plantarum P1 improved the texture of meat analogues. Press cakes fermentation reduced bitterness, increased juiciness, and balanced the taste of meat analogues. Fermented soy press cake was recommended for the production of meat analogues.

Edge weights in a protein elastic network reorganize collective motions and render long-range sensitivity responses.

The effects of inter-residue interactions on protein collective motions are analyzed by comparing two elastic network models (ENM)-structural contact ENM (SC-ENM) and molecular dynamics (MD)-ENM-with the edge weights computed from an all-atom MD trajectory by structure-mechanics statistical learning. A theoretical framework is devised to decompose the eigenvalues of ENM Hessian into contributions from individual springs and to compute the sensitivities of positional fluctuations and covariances to spring constant variation. Our linear perturbation approach quantifies the response mechanisms as softness modulation and orientation shift. All contacts of Cα positions in SC-ENM have an identical spring constant by fitting the profile of root-of-mean-squared-fluctuation calculated from an all-atom MD simulation, and the same trajectory data are also used to compute the specific spring constant of each contact as an MD-ENM edge weight. We illustrate that the soft-mode reorganization can be understood in terms of gaining weights along the structural contacts of low elastic strengths and loosing magnitude along those of high rigidities. With the diverse mechanical strengths encoded in protein dynamics, MD-ENM is found to have more pronounced long-range couplings and sensitivity responses with orientation shift identified as a key player in driving the specific residues to have high sensitivities. Furthermore, the responses of perturbing the springs of different residues are found to have asymmetry in the action-reaction relationship. In understanding the mutation effects on protein functional properties, such as long-range communications, our results point in the directions of collective motions as a major effector.

Profiles of sturgeon protein prepared by two methods and the correlation between protein fractions and functional properties

SummaryIn order to find the potential functional components in sturgeon protein, the protein fractions and functional properties of sturgeon proteins (SP) prepared by two methods were investigated, including pH‐shift and subcritical dimethyl ether extraction (SDEE). In the case of the former method, four different experimental conditions were followed. The SP prepared by alkali‐aided pH‐shift had the highest salt‐soluble protein content as well as the lowest water‐soluble protein content, while the highest water‐soluble protein content was observed in SDEE‐produced SP due to a higher proportion of water‐soluble protein that was retained during SDEE. Besides, the significant variations in almost all detected myofibrillar and sarcoplasmic fractions were observed across protein samples, which was mainly due to the solubility of various proteins under different preparation conditions. Moreover, the SDEE‐produced SP possessed the greatest capacities in all the emulsification, foaming and gelation, followed by alkali‐aided pH‐shift and acid‐aided pH‐shift. In addition, the correlation analysis results indicated that enolase, aldolase, PM‐2, TI, NDK, parvalbumin, actin and tropomyosin might be the primary functional components, while PM‐1, CK, MLC3, degradation products and lipids had negative effects on its functional properties. Therefore, changes of the above components might be another important reason to explain how different methods affect the quality of protein, except for the degradation of protein.

Investigation on physicochemical, structural, and functional properties of protein from pecan (Carya illinoinensis (wangenh.) K. Koch) treated by three different peeling methods

Investigation on physicochemical, structural, and functional properties of protein from pecan (Carya illinoinensis (wangenh.) K. Koch) treated by three different peeling methods

Modulating molecular interactions in pea protein to improve its functional properties

Proteins exist in numerous spatial arrangements and are stabilized by various inter- and intra-molecular forces. The objectives of this study were to investigate the functional properties of pea protein isolate in terms of water/oil holding capacity, emulsifying and foaming properties, solubility, and gelation by modulating protein covalent and non-covalent interactions with specific denaturants/modifiers and to understand the physicochemical characteristics (e.g., free amino group content, free sulfhydryl group content, surface hydrophobicity, SDS-PAGE profile, secondary structures) of the unfolded pea proteins that are responsible for the functional changes. All the denatured proteins possessed significantly increased solubility. Both urea and SDS unfolded proteins had significantly higher water holding capacity and oil holding capacity of up to 5.01 and 5.09 g H 2 O/g, and 3.06 and 2.84 g oil/g compared with the control pea protein (4.12 g H 2 O/g and 1.29 g oil/g), respectively. The proteins unfolded with urea or SDS also showed improved emulsification properties. The trypsin hydrolyzed protein exhibited the highest foaming capacity and better gelation properties among all the treatments. Principal component analysis indicated strong associations between protein functional and physicochemical properties and molecular interactions. This study provides useful fundamental knowledge in tailoring protein structures in order to enhance its functionalities and broaden the food applications. • Both urea and SDS unfolded pea proteins had improved water/oil holding capacity. • Trypsin hydrolyzed protein had improved foaming and gelation properties. • All the denatured proteins possessed increased solubility. • Proteins unfolded with urea or SDS showed improved emulsifying properties. • The study provides knowledge in tailoring protein structure for improved functionality.